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Thread: Take the highest MP count you can get....or

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    Take the highest MP count you can get....or

    Guy mentioned if two cameras were on a table he would take the one with the highest MP. He is not alone, for sure.

    But's it's very interesting to hear what the inventor of CMOS sensors has to say on exactly this issue:

    https://youtu.be/JkBh71zZKrM

    This is a long lecture at Yale I think, but you can just forward to 38 minutes where he talks about the problems with small pixels and how marketing is trumping engineering and physics with high mp cameras like the A7r2. It's really worth a listen as he basically says: high MP counts "sell", so we make them, despite the fact they are not better because of the diffraction limit.

    I did not get to this video as a way to "bash" the A7r2, which is obviously a very nice camera. I'm not mentioning the "L" word here at all. What got me here was another discussion about whether lens performance in general can vary at an aperture like f/11 or F/16.

    In trying to understand this issue I came across articles which claimed the diffraction limit was f/13 on a 12mp FF but f/11 on a 24mp FF camera. Several of these stated outright, that unless you planned on shooting fast all the time, a larger pixel was more desirable because diffraction did not set in so soon and thus you could use f/11 and f/16 to full effect when you wanted DOF.

    Now some think when you downsize a 42mp to 24mp the diffraction effects, which are greater at f/11, will magically disappear and the two images will be the same.

    I don't really know, but I would like to find out, because I do shoot alot of landscapes and I do use f/11 often

    I can't say I don't find it interesting the inventor of CMOS basically says outright: the MP race is a marketing scam. I'm not qualified to say to what degree it's true or not, but again I'd like to understand the issues better.

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    Re: Take the highest MP count you can get....or

    Why post it here? A 16mp m43 sensor has smaller pixels and a higher pixel density.

    Other than the RX100 cams, Sony cams with interchangeable lenses all have larger pixels.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by uhoh7 View Post
    Guy mentioned if two cameras were on a table he would take the one with the highest MP. He is not alone, for sure.

    But's it's very interesting to hear what the inventor of CMOS sensors has to say on exactly this issue:

    https://youtu.be/JkBh71zZKrM

    This is a long lecture at Yale I think, but you can just forward to 38 minutes where he talks about the problems with small pixels and how marketing is trumping engineering and physics with high mp cameras like the A7r2. It's really worth a listen as he basically says: high MP counts "sell", so we make them, despite the fact they are not better because of the diffraction limit.

    I did not get to this video as a way to "bash" the A7r2, which is obviously a very nice camera. I'm not mentioning the "L" word here at all. What got me here was another discussion about whether lens performance in general can vary at an aperture like f/11 or F/16.

    In trying to understand this issue I came across articles which claimed the diffraction limit was f/13 on a 12mp FF but f/11 on a 24mp FF camera. Several of these stated outright, that unless you planned on shooting fast all the time, a larger pixel was more desirable because diffraction did not set in so soon and thus you could use f/11 and f/16 to full effect when you wanted DOF.

    Now some think when you downsize a 42mp to 24mp the diffraction effects, which are greater at f/11, will magically disappear and the two images will be the same.

    I don't really know, but I would like to find out, because I do shoot alot of landscapes and I do use f/11 often

    I can't say I don't find it interesting the inventor of CMOS basically says outright: the MP race is a marketing scam. I'm not qualified to say to what degree it's true or not, but again I'd like to understand the issues better.
    That other thread was shut down. It seems that you want to restart the arguments all over again. Why don't you just accept that we are all a bunch of fools buying a 42MP camera, declare victory and go home.
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    Re: Take the highest MP count you can get....or

    C'mon. Be nice.

    It's a legitimate question - go for higher megapixels at the same sensor dimensions or not. I think that now that sensors are capable of managing noise very well there's little to recommend lower pixel count.

    I can tell you from experience with the Sony A7R and the A7RII the extra pixels are a real benefit, especially in the case where you want to crop an image. I am not sure I could tell the difference in prints smaller than 20x30 (yes I have the prints).

    I like the combination of a full frame 35mm sensor and 42 megapixels. The next camera I will look at will be the Leica SL, but with 24 megapixels it will be a hard sell to replace my A7RII.
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    Re: Take the highest MP count you can get....or

    It will be interesting to see a comparison of the Pentax 645Z (or IQ150/250 or any MFDB with Sony 33x44) sensor against the Sony A7RII. Based on OP, the 645Z with 1.7x the real estate should be noticeable better, but from what I have read so far (Lula review), this appears not to be the case.

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    Re: Take the highest MP count you can get....or

    You can always go up in megapixels and sensor size, right up to 80MP and beyond.

    At some point it comes down to what you like to shoot. For me that has never pushed me into MF, but it's personal taste.

    For me 35mm and small camera body is a sweet spot.
    Brad Husick
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by bradhusick View Post
    C'mon. Be nice.

    It's a legitimate question - go for higher megapixels at the same sensor dimensions or not. I think that now that sensors are capable of managing noise very well there's little to recommend lower pixel count.

    I can tell you from experience with the Sony A7R and the A7RII the extra pixels are a real benefit, especially in the case where you want to crop an image. I am not sure I could tell the difference in prints smaller than 20x30 (yes I have the prints).

    I like the combination of a full frame 35mm sensor and 42 megapixels. The next camera I will look at will be the Leica SL, but with 24 megapixels it will be a hard sell to replace my A7RII.
    TY Brad

    For Fossum, the issue is not noise but the lower diffraction threshold of smaller pixels. I agree, noisewise the A7r2 seems around the same performance as A7II, but it can't compare to the A7s, which is shooting with much less noise at high ISO. But 10mp is really a big difference vs 24, 36 or 42.

    I'm not trying to insult anyone here. But the 42mp is considered a major selling point of the camera, and taken for granted as "better" by many good shooters. I should not mention evidence to the contrary? Not the right place for it?

    I own and shoot Sony every day, and certainly I have considered the A7r2. This seems totally relevant as a topic of discussion here. I honestly do not yet understand how this limitation of smaller pixels effects us, but it certainly seems like a good question, some might want to understand before they spend 3 grand.

    People disagree about all sorts of stuff on photography forums, much of what I've learned has been when somebody has cared enough challenge my pre-conceptions. If everyone always agrees, what is there to discuss?

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    Re: Take the highest MP count you can get....or

    Okay let me take a stab at answering this. Actually he is correct but slightly misrepresenting a little.

    Let's take a Phase One IQ 180 back which is a 80 MPX back with a believe a 5.4 micron sensor. This baby is big but and this will depend on lens and its resolving power , very important . But with a Rodenstock tech cam lens you will start seeing diffraction coming in around F8. Sony and most of there high quality lenses it starts at F11. In all my tests I have done I see it every time on the Sonys that the image is starting to degrade. It's very slight and yes you start losing a little resolution but not down to a 24mpx sensor and even those sensors it's about F11 also. So yes once you start getting past F11 things will degrade to lower levels. Now it may happen slightly faster on the 42 MPX sensor over a 24mpx sensor because of the smaller pixel pitch but by and large that is very small. Now many landscape shooters will go to F11 to gain the DOF but knowing there in that diffraction range. Best technique is to focus stack. Most 35mm lens there optimum resolving power is F5.6 to F8. So best practice to gain the best resolving power is to shoot right in that zone but to gain DOF you do a focus stack of maybe 3 zones of focus. Also I should point out this is where Tilt becomes a very valuable tool both in Medium format and 35mm is you can tilt to gain a wider path of DOF without stopping down more. Why many landscape shooter will Cary TSE lenses or MF folks use tech cams.

    Now he is correct but I would not go as far to say what's the point of higher MPX cams both 24,36 and 42 MPX sensors will diffract but given this format size it's very small when that will happen.

    Honestly most folks would never know the difference unless there looking at things 100 percent on screen and even than its a little underwhelming the effect. To really see it shoot something at F8 and F22 you should see it a lot easier.

    No question I would pick a higher MPX. My client just emailed me tonight letting me know one of my shots there CEO loved and wants it printed really big in his office. As I said you just never know when you get that amazing shot and you need to go big. But I agree 24mpx is a very nice sweat spot until someone wants big or crop the hell out of your image. Rather have that elbow room myself. Besides all the technical reasons we are gear sluts it big or go home. Lol

    Now having said all that 24mpx most folks may never need bigger why the comment on the marketing from him and he is correct. Let's be honest if your a OEM your going to market it no question. That's marketing we will never get away from it. Everyone of them do it and no one is excluded either. I read some of this marketing stuff and some of it is a joke to think we are that stupid but in general the average Joe des not know any better and it becomes a big selling point. We can't blame anyone for any of that because people will buy it.
    Photography is all about experimentation and without it you will never learn art.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by jagsiva View Post
    It will be interesting to see a comparison of the Pentax 645Z (or IQ150/250 or any MFDB with Sony 33x44) sensor against the Sony A7RII. Based on OP, the 645Z with 1.7x the real estate should be noticeable better, but from what I have read so far (Lula review), this appears not to be the case.
    The real difference will come down to tonal range and smoother transition because of the bigger sensor. Better said it looks smoother but that gap is getting smaller. They really are Sony sensors . I tested the leaf cmos back , same sensor as the Pentax and it's a great sensor but it's not really night and day, it's close.
    Photography is all about experimentation and without it you will never learn art.

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    Re: Take the highest MP count you can get....or

    Something I should point out. Lenses have a maximum resolving power at a given aperture you get past that aperture you start losing the resolving power and at the same time your getting into that diffraction area , so your getting dinged twice just by going past the point of optimum IQ. Case in point I would rarely if ever go to F16 and the only reason would be I'm forced too because I can't focus stack let's say. Most high quality 35 lenses the highest resolving power is in that F 5.6 to F8 range but need to know once you hit F11 your on the downward slide like diffraction. So it's a balance of lens and diffraction.
    Photography is all about experimentation and without it you will never learn art.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by uhoh7 View Post
    TY Brad

    For Fossum, the issue is not noise but the lower diffraction threshold of smaller pixels. I agree, noisewise the A7r2 seems around the same performance as A7II, but it can't compare to the A7s, which is shooting with much less noise at high ISO. But 10mp is really a big difference vs 24, 36 or 42.

    I'm not trying to insult anyone here. But the 42mp is considered a major selling point of the camera, and taken for granted as "better" by many good shooters. I should not mention evidence to the contrary? Not the right place for it?

    I own and shoot Sony every day, and certainly I have considered the A7r2. This seems totally relevant as a topic of discussion here. I honestly do not yet understand how this limitation of smaller pixels effects us, but it certainly seems like a good question, some might want to understand before they spend 3 grand.

    People disagree about all sorts of stuff on photography forums, much of what I've learned has been when somebody has cared enough challenge my pre-conceptions. If everyone always agrees, what is there to discuss?
    The thing is I thought you already got your answer from your recent FredMiranda thread on diffraction. Lens's diffraction doesn't depend on the resolution of the sensor. It's an optical phenomenon. If a lens peaks at f/4 (we're talking about center here), it will peak at that aperture on any recording medium. Higher resolution sensor just makes thing easier to spot the drop in higher frequency contrast (smaller details).

    Of course, physics-wise, as the sensor gets denser, each pixel would receive less total light. Hence the noise at pixel level is always worse with the higher MP of the same tech generation. BSI in the A7RII helps because it reduces the travelling distance of photons from the microlens to the electron converter.

    But realistically, is there anyone here going to look at photo at 1:1 all the time? So pixel-level noise is irrelevant. That's why people are comparing different MPs at a common size (whether for web display or for print). Scaling down a picture would average out the noise; the more you scale, the smoother it looks.

    And I do hope this is not about Leica (24MP) vs. Sony (42MP) again.

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    Re: Take the highest MP count you can get....or

    IIRC isn't diffraction simply a function of the width of the lens opening?
    Diffraction is not a function of the f number, i.e. width/focal length, or the sensor.
    So larger formats than FF will suffer later, at higher f-numbers.

    My FF Leica lenses seem to be affected by diffraction typically by f/8 or f/11.
    However, the APO-Telyt-R 280/4 is already diffraction limited wide open.

    High MP FF sensors can nevertheless still be very useful and desirable, at least to me.
    With best regards, K-H.

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    Re: Take the highest MP count you can get....or

    To add, the talk is regarding capturing an image on the sensor, it doesn't take into consideration making prints.

    If you have a 24mp camera and need to print 30", a 200% enlargement has a more negative impact on IQ than the diffraction impact on a 50mp camera at it's native 100%. This is where mp's matter, however if you're never going to make prints, then yes there's no need for anything higher.

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    Re: Take the highest MP count you can get....or

    Well, how about cropping?
    With best regards, K-H.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by uhoh7 View Post
    TY Brad

    I'm not trying to insult anyone here. But the 42mp is considered a major selling point of the camera, and taken for granted as "better" by many good shooters. I should not mention evidence to the contrary? Not the right place for it?
    I don't think that the 6+ MP is what sells the camera. The slight IQ difference with respect to the A7r is rather due to the new technology used :

    1) The back side illuminated sensor (BSI).
    2) Then the on sensor PDAF, which is very efficient working in tandem with CDAF.
    3) Add IBIS

    and this body ticks all you need for a good picture (except those needing tracking AF for fast action). Personally I see too many pixels as a draw back for many because it eats storage space like mad and suppose higher processing resources. People are very aware of that.

    Also diffraction kicking in earlier with higher pixels density is nothing new. It has already been abundantly discussed with the Nikon D800 and the A7r (F8 being judged the sweet spot, smaller than that diffraction begun to kick in). It has even been discussed for MFT sensors where you try to keep your lens at F5.6 or wider to avoid it.

    One can use focus stacking to avoid the lack of DOF. Olympus for instance has announced they would implement that feature directly in the body with a firmware update for both the E-M1 and E-M5II. Rumors say that the E-M1II will get 20MB, which could explain why they are working on that feature.
    Last edited by Annna T; 3rd November 2015 at 23:55.

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    Re: Take the highest MP count you can get....or

    Sony advertises the A7RII has diffraction-reducing technology. What it does is a complete mystery but since there is some solution of either hardware or software I don't think you can just single out the A7RII as a sample of high megapixel causing diffraction. I believe BSI also increases diffraction.
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    Re: Take the highest MP count you can get....or

    Deleting all images except for the best keepers certainly will free up a lot of disk space for me!
    With best regards, K-H.
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Slingers View Post
    Sony advertises the A7RII has diffraction-reducing technology. What it does is a complete mystery but since there is some solution of either hardware or software I don't think you can just single out the A7RII as a sample of high megapixel causing diffraction. I believe BSI also increases diffraction.
    No, diffraction is a lens property AFAIK!
    It is a function of the opening diameter of the lens.
    It just reflects the wave nature of light.
    Of course with good lenses and sensors one notices it earlier.

    IIRC Olympus does something similar for their native lenses.
    I read somewhere it's a form of convolution sharpening.
    Can somebody please fill us in with the correct info? Thanks.
    With best regards, K-H.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by k-hawinkler View Post
    No, diffraction is a lens property AFAIK!
    It is a function of the opening diameter of the lens.
    It just reflects the wave nature of light.
    Of course with good lenses and sensors one notices it earlier.

    IIRC Olympus does something similar for their native lenses.
    I read somewhere it's a form of convolution sharpening.
    Can somebody please fill us in with the correct info? Thanks.
    I believe diffraction is from a combination of lens and sensor.

    Also I don't think diffraction is not all of a bad thing as it's the reason for sun stars.
    Last edited by Slingers; 4th November 2015 at 00:48.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Slingers View Post
    I believe BSI also increases diffraction.
    I would think the opposite since the active photosite area is larger with no vignetting from the circuitary above such a one in a regular CMOS.
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Vivek View Post
    I would think the opposite since the active photosite area is larger with no vignetting from the circuitary above such a one in a regular CMOS.
    My understanding is that BSI increases pixel crosstalk which then also increases diffraction due to less light reaching the pixels with red, green and blue each getting different amounts of light.

    It's possible I am wrong though as I just searched for reputable source to link but couldn't find it.

    EDIT: after reading some more I was wrong as it seems it was the older bsi sensors that suffered from crosstalk. New technology like samsung's isocell or olympus' stacked bsi doesn't have the same problems.
    Last edited by Slingers; 4th November 2015 at 02:52.
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    Re: Take the highest MP count you can get....or

    Should be pretty easy to make a real world test.
    I'm sure some of You own both a7ii and a7rii:
    Same lens, same focus point, same apertures 5,6/8/11/16.
    Let's ses what come through..
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    Re: Take the highest MP count you can get....or

    Craig, Yes, technology has improved enormously. There was even a significant jump from the NEX-5 to NEX-5N sensor (smaller pixels but much better results).

    Of course, it OK to be talking about old/archaic stuff since the L brand is invoked.
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by k-hawinkler View Post
    Well, how about cropping?
    Yep, that was my thought exactly. Having a higher pixel density sensor will allow you to have a higher res crop. To me, that is a major reason for wanting more pixels.

    Joel

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    Re: Take the highest MP count you can get....or

    The point the speaker made in the video is that its the um size of the photo site related to the resolving power of a lens.
    His point, to quote; "its the physics"

    He said that optimum photo site size is about 5 um and that large MP count 24x35mm sensors are getting well below that size as the MP count goes up.

    Presuming that he knows what he's talking about its simple: to achieve maximum resolving power from a lens use a sensor with approximately 5 um photo site.

    The more important test, in my view, is to shot something on a 5 um sensor with a lens, then shot the same scene on a 2 um sensor with the same lens, then print both of them, using the same printer to something like 40x60 inches and see which one is more impressive.

    I haven't bothered trying to see where defraction begins to degrade images. I accept the common statement that its about F11. So, I tend to use that as minimum aperture.

    I agree with Guy's inclination that high pixel count will mean I can print bigger if I want to and that's where its important. For most other applications we are throwing away most of the pixels to get an image down to a useful size.
    David

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    Re: Take the highest MP count you can get....or

    from a physics point of view, it all depends on the resolving power of the lens.
    Lets pick, for example, the Leica APO-Summicron-M 50mm f/2 as an example of a reasonably sharp lens with good resolving power.
    Looking at its MTF graph you see at f/5.6 you see 80% contrast at 40 line pairs per mm.
    To resolve a line pair you must sample it at least twice the periodicity of the signal according to Shannon sampling criteria. If it were to be sampled less frequently, then the pair would merge and would not be resolved.
    So that means to resolve what that lens produces at 80% contrast one must have at least 80 sensor sites per mm.
    1/80 yields a pitch of 12.5 micron.
    Most real lenses don't have a sharp cut-off in resolving power, it is just that the contrast (or signal to noise ration) simply declines as the frequency is increased.
    So I think, although it is not on Leica's chart, that that lens will provide at least 50% contrast at 80LP per mm. The lens will indeed pass higher frequencies, it is just that the contrast will drop as the frequency goes up. So what is your taste for the minimum contrast ratio that you would consider to be acceptable from a resolving power point of view?
    The idustry has used 50% for a long time as an engineering benchmark.
    So lets say we do and assume that this lens will produce 50% or better contrast at 80LP/mm
    that means it needs a sensor pitch of 6.25 micron at the largest to give us enough information to resolve the signal.
    it also means that anything larger will simply not give you what the lens is capable of producing.
    Anything smaller will then be in the territory of over-sampling the signal which unfortunately may lead to other phenomenon none of which is particularly pretty.
    So in other words, I tend to agree that unless lenses get a whole lot better, a pixel pitch smaller than say 5 microns or so will not give you more information. More pixels, yes, but no more information.
    Thus assuming one wants to print large, even having more pixels than that will not actually give you more information on the print.
    The simple reason is that is just not there unless you are satisfied with very low contrast in that information.
    Of course limiting the sample frequency does produce the effect of a resolution cut-off filter, but unless the lens produces more information, more frequent sampling just won't deliver the goods.
    So for a full frame 35mm sensor, anything more than 24Mpx is not theoretically beneficial.
    If you really want more information, and assuming the lenses are up to it, what you need is a larger sensor, not more pixels per inch.
    -bob
    Last edited by Bob; 4th November 2015 at 09:17.
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    Re: Take the highest MP count you can get....or

    Well, considering a better lens one might come to a different conclusion, no?
    With best regards, K-H.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Bob View Post
    from a physics point of view, it all depends on the resolving power of the lens.
    Lets pick, for example, the Leica APO-Summicron-M 50mm f/2 as an example of a reasonably sharp lens with good resolving power.
    Looking at its MTF graph you see at f/5.6 you see 80% contrast at 40 line pairs per mm.
    To resolve a line pair you must sample it at least twice the periodicity of the signal according to Shannon sampling criteria. If it were to be sampled less frequently, then the pair would merge and would not be resolved.
    So that means to resolve what that lens produces at 80% contrast one must have at least 80 sensor sites per mm.
    1/80 yields a pitch of 12.5 micron.
    Most real lenses don't have a sharp cut-off in resolving power, it is just that the contrast (or signal to noise ration) simply declines as the frequency is increased.
    So I think, although it is not on Leica's chart, that that lens will provide at least 50% contrast at 80LP per mm. The lens will indeed pass higher frequencies, it is just that the contrast will drop as the frequency goes up. So what is your taste for the minimum contrast ratio that you would consider to be acceptable from a resolving power point of view?
    The idustry has used 50% for a long time as an engineering benchmark.
    So lets say we do and assume that this lens will produce 50% or better contrast at 80LP/mm
    that means it needs a sensor pitch of 6.25 micron at the largest to give us enough information to resolve the signal.
    it also means that anything larger will simply not give you what the lens is capable of producing.
    Anything smaller will then be in the territory of over-sampling the signal which unfortunately may lead to other phenomenon none of which is particularly pretty.
    So in other words, I tend to agree that unless lenses get a whole lot better, a pixel pitch smaller than say 5 microns or so will not give you more information. More pixels, yes, but no more information.
    Thus assuming one wants to print large, even having more pixels than that will not actually give you more information on the print.
    The simple reason is that is just not there unless you are satisfied with very low contrast in that information.
    Of course limiting the sample frequency does produce the effect of a resolution cut-off filter, but unless the lens produces more information, more frequent sampling just won't deliver the goods.
    So for a full frame 35mm sensor, anything more than 24Mpx is not theoretically beneficial.
    If you really want more information, and assuming the lenses are up to it, what you need is a larger sensor, not more pixels per inch.
    -bob
    Mystery solved.

    In fact, a couple of mysteries solved.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by k-hawinkler View Post
    Well, considering a better lens one might come to a different conclusion, no?
    Sure,
    Have an example?
    -bob

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    Re: Take the highest MP count you can get....or

    Hi,

    Well, I have a great respect for Mr. Fossum but that presentation was quite a few years ago. Things develop quite a lot in five years. What happens is that design rules get smaller. A single junction (transistor) get smaller, that means that optimum resolution shifts. With 500 nm resolution, it may be that 8 MP is optimal, but with 180 nm technology used today 54 MP may be optimum. Modern sensors are also much simple designs, so sensor to wiring ratio has been much improved.

    Now, getting back to diffraction. Diffraction is really benign to sharpening there is some empirical research indicating that say 36 MP stopped down to f/22 still beats 24 MP stopped down to f/8, once optimal sharpening is applied. Check here: https://www.onlandscape.co.uk/2012/0...-is-too-small/

    There is also empirical research showing that putting a mediocre zoom on a 36 MP DSLR beats the best of class zoom on a 21 MP camera.
    LensRentals.com - Roger Buys a Camera System: A 24-70mm System Comparison

    The final issue is that the resolution of the lens should not exceed the resolution of the sensor. Once this happens the sensor will show a lot of detail, all of which is fake. So it is better to have high resolution sensor that actually resolves the detail than a sensor that cannot resolve the detail and turns it in artefacts. OK, the correct image will look soft at actual pixels and the low resolution will show a lot of fake detail at reasonable contrast.

    The simple fact is that high resolution is always good. A high resolution sensor will always give better detail with smoother contours and more malleable images, until pixels get that small that resolution is lost. There is a limit to resolution, but it is not at 12, 16 or 24 MP on a full frame sensor. Correct rendition with the best lenses today may require as much as 250-300 MP.

    Best regards
    Erik






    Quote Originally Posted by uhoh7 View Post
    Guy mentioned if two cameras were on a table he would take the one with the highest MP. He is not alone, for sure.

    But's it's very interesting to hear what the inventor of CMOS sensors has to say on exactly this issue:

    https://youtu.be/JkBh71zZKrM

    This is a long lecture at Yale I think, but you can just forward to 38 minutes where he talks about the problems with small pixels and how marketing is trumping engineering and physics with high mp cameras like the A7r2. It's really worth a listen as he basically says: high MP counts "sell", so we make them, despite the fact they are not better because of the diffraction limit.

    I did not get to this video as a way to "bash" the A7r2, which is obviously a very nice camera. I'm not mentioning the "L" word here at all. What got me here was another discussion about whether lens performance in general can vary at an aperture like f/11 or F/16.

    In trying to understand this issue I came across articles which claimed the diffraction limit was f/13 on a 12mp FF but f/11 on a 24mp FF camera. Several of these stated outright, that unless you planned on shooting fast all the time, a larger pixel was more desirable because diffraction did not set in so soon and thus you could use f/11 and f/16 to full effect when you wanted DOF.

    Now some think when you downsize a 42mp to 24mp the diffraction effects, which are greater at f/11, will magically disappear and the two images will be the same.

    I don't really know, but I would like to find out, because I do shoot alot of landscapes and I do use f/11 often

    I can't say I don't find it interesting the inventor of CMOS basically says outright: the MP race is a marketing scam. I'm not qualified to say to what degree it's true or not, but again I'd like to understand the issues better.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Bob View Post
    So for a full frame 35mm sensor, anything more than 24Mpx is not theoretically beneficial.
    If one takes that as true, the whole of m43rds, the top tier Canon, Nikon and Sony cameras can be summarily dismissed as ineffective.

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    Re: Take the highest MP count you can get....or

    Hi,

    I see a couple of problems with your reasoning.

    1) It is quite true that 50% (or 35%) MTF is an often used criterium for perceived sharpness, but that reasoning excludes sharpening which is a part of the digital work flow. I guess no one with argue that it is good to achieve say 50% MTF at 180 PPI in print without sharpening. But it may matter little if it is native MTF from the lens or achieved by sharpening.

    2) Now, consider two cases, say you make an A2 size print from a camera that delivers 50% MTF at 180 PPI and is limited to 180 PPI which would correspond to 16 MP. Now let's put the same lens on a camera with 64 MP. That camera would still produce at least 50% MTF at 180 MPI. Actually, it would produce quite a bit more as system MTF is MTF (lens) * MTF (sensor) and MTF of the 64MP sensor will be higher at 180 PPI than that of the 16 MP sensor.

    3) The higher resolution sensor will still give a lot of detail once you go beyond A2 size.

    I am pretty sure I have actually seen this in prints. I have shot 16 MP pictures which I felt were more usable than 24 MP pixels . Technically this was a newer generation APS-C sensor compared with older generation FF. This was under windy condition with both shutter speed, accurate focusing and shutter speed being an issue. The APS-C camera had live view, allowing more accurate focusing. With the APS-C camera I needed a shorter focal length so I could use a slightly better lens. The APS-C camera also had a cleaner high ISO, so I could have a shorter shutter time. Both images printed fine in A2 size.

    On the other hand I have seen very little advantage from 39 MP MF over my APS-C sensor at A2 size. Going to A1 which is 41% larger (in linear dimension) I felt the 39 MP MF came to advantage.

    So, what I see is that more megapixels actually yield a better image. But, you have to work for it. Also, it may be that the advantage of more pixels may be visible only in relatively large prints.

    These are of course just reflections of what I have seen in my own work. My standard print size is A2, around 16"x23", with a few 30"x40".

    Best regards
    Erik


    Quote Originally Posted by Bob View Post
    from a physics point of view, it all depends on the resolving power of the lens.
    Lets pick, for example, the Leica APO-Summicron-M 50mm f/2 as an example of a reasonably sharp lens with good resolving power.
    Looking at its MTF graph you see at f/5.6 you see 80% contrast at 40 line pairs per mm.
    To resolve a line pair you must sample it at least twice the periodicity of the signal according to Shannon sampling criteria. If it were to be sampled less frequently, then the pair would merge and would not be resolved.
    So that means to resolve what that lens produces at 80% contrast one must have at least 80 sensor sites per mm.
    1/80 yields a pitch of 12.5 micron.
    Most real lenses don't have a sharp cut-off in resolving power, it is just that the contrast (or signal to noise ration) simply declines as the frequency is increased.
    So I think, although it is not on Leica's chart, that that lens will provide at least 50% contrast at 80LP per mm. The lens will indeed pass higher frequencies, it is just that the contrast will drop as the frequency goes up. So what is your taste for the minimum contrast ratio that you would consider to be acceptable from a resolving power point of view?
    The idustry has used 50% for a long time as an engineering benchmark.
    So lets say we do and assume that this lens will produce 50% or better contrast at 80LP/mm
    that means it needs a sensor pitch of 6.25 micron at the largest to give us enough information to resolve the signal.
    it also means that anything larger will simply not give you what the lens is capable of producing.
    Anything smaller will then be in the territory of over-sampling the signal which unfortunately may lead to other phenomenon none of which is particularly pretty.
    So in other words, I tend to agree that unless lenses get a whole lot better, a pixel pitch smaller than say 5 microns or so will not give you more information. More pixels, yes, but no more information.
    Thus assuming one wants to print large, even having more pixels than that will not actually give you more information on the print.
    The simple reason is that is just not there unless you are satisfied with very low contrast in that information.
    Of course limiting the sample frequency does produce the effect of a resolution cut-off filter, but unless the lens produces more information, more frequent sampling just won't deliver the goods.
    So for a full frame 35mm sensor, anything more than 24Mpx is not theoretically beneficial.
    If you really want more information, and assuming the lenses are up to it, what you need is a larger sensor, not more pixels per inch.
    -bob

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    Re: Take the highest MP count you can get....or

    i think it was Smokey Yunick of Nascar fame whose relevant quote was "there's no substitute for cubic inches" you can fit the metaphor to your own liking in this context...

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Bob View Post
    Anything smaller will then be in the territory of over-sampling the signal which unfortunately may lead to other phenomenon none of which is particularly pretty.
    Isn't one of the things it can do however, is render smoother tonality? When oversampling by a factor of N, the dynamic range increases by log2(N) bits, because there are N times as many possible values for the sum. (Hence one reason we typically get more DR as sensor resolution goes up past the 24MP point on 35mm sensors.) Of course noise goes up too, but raw algorithms have gotten very good at dealing with it (averaging). So while the data may be an interpolation and not "real," it gets implemented in a way most photographers (or audiophiles) pleasing -- the smoothing out of harsher point-to-point transitions between rapidly changing values. Analog film did this as well through halation (and analog tube-amp audio did it through latency).
    Jack
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    Re: Take the highest MP count you can get....or

    Hi,

    Oversampling is always good. It is undersampling that is bad. Oversampling yields smooth countours, undersampling gives jagged contours just as an example.

    Regarding noise it is mostly dependent on the number of photons collected. It doesn't matter if those photons are collected on an 8MP, 16 MP, 36MP or 42MP as long as similar technology is used. A larger sensor will collect more photons, there a full frame 24 MP sensor will have less noise than a 24 MP APS-C sensor. (*)

    Regarding dynamic range it may decrease a bit with pixels size, according to the math at least, but that decrease has been met with better readout noise from modern sensors.

    So smaller pixels are mostly advantageous. The exception is really high ISO capability where large pixels are at some advantage. (**)

    Best regards
    Erik

    (*) This is not entirely true. With smaller pixels there will be more wiring so photodetector area to wiring area ratio will worsen. But design rules also shrink, so wiring area also gets thinner as sensor making technology develops. For each generation of technology there will be an optimum megapixel count.

    (**) DR is normally defined as Full Well Capacity / Readout Noise. If we merge two pixels we double FWC but readout noise is the same. Now if we do it in software FWC will be the same as with the bigger pixel, but readout noise will be 41% (square root of 2) higher.

    In the figures below you can see that DR increases a bit when Sensor+ kicks in on the IQ-180 but the noise curve is not affected. On screen there would be a dramatic change if we viewed the image at actual pixels, but activating sensor plus is like going from 100% view to 50% view. For those who don't know Sensor+ it is a Phase One technology doing pixel binning in hardware. So when Sensor+ is activated 4 pixels will be interconnected and form one pixel. Megapixels go down to 25% while linear resolution is halved. That binning is a Phase One invention and it avoids colour sampling errors. Quite smart.
    Click image for larger version. 

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    Quote Originally Posted by Jack View Post
    Isn't one of the things it can do however, is render smoother tonality? When oversampling by a factor of N, the dynamic range increases by log2(N) bits, because there are N times as many possible values for the sum. (Hence one reason we typically get more DR as sensor resolution goes up past the 24MP point on 35mm sensors.) Of course noise goes up too, but raw algorithms have gotten very good at dealing with it (averaging). So while the data may be an interpolation and not "real," it gets implemented in a way most photographers (or audiophiles) pleasing -- the smoothing out of harsher point-to-point transitions between rapidly changing values. Analog film did this as well through halation (and analog tube-amp audio did it through latency).

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    Re: Take the highest MP count you can get....or

    Hi,

    I would agree, with some small remarks.

    1) Having a slightly larger sensor with a similar pixel count makes the pixels larger. The larger size of pixels makes less demands on the lens. So the lens on the Sony may need to perform say 25-35% better than a lens on the 50 MP CMOS back to yield the same fine detail contrast.

    The other point is that as both sensors use similar generation technology, so noise levels per sensor area will be about the same. But, the 50MP CMOS sensor being larger it will have it will have a slightly better Signal to Noise Ratio (SNR). Not a dramatic difference just corresponding to 2/3 EV exposure change.

    2) Now, in a real world we probably have plenty of SNR with any modern imaging system at low ISO, assuming the sensor is not too small. So the real advantage of that larger sensor will show at high ISO. High ISO has not been the forte of MFD, but that has been due to the relatively noisy readout of the CCD sensor combined with low quantum efficiency. With the CMOS based MFD sensors this turns around. The Pentax 645Z is probably the best performing camera of all at high ISO. The other CMOS backs are probably as good in a real world just a bit restrained by reality :-)

    The 645Z should have a 2/3 stop advantage over say a Canon 5DIII at high ISO and it probably has. So you now can put your 85/1.4 Otus on the Pentax and have 2/3 stop advantage over the Canon 5DIII.

    3) Just to explain, the Canon sensor is a different story. Canon sensors have noisy readout, so they cannot deliver the dynamic range of the Sony sensors at base ISO. But the signal coming of the sensor i actually quite clean, the purity is lost in the AD-converter. At high ISO the image is underexposed so amplification (analogue gain) is applied to the signal before AD-conversion. The camera makes good use of the sensor and the camera shines at high ISO. But, high ISO will not help with shot noise :-(

    4) Now, why are Sony sensors that good at low ISO? They use a large number of simple but accurate ADCs situated on the sensor chip. So connections are short. There is an ADC for each column of pixels so each converter handles just a few thousand pixels.

    Sony is not exactly alone with this technology. Leica has it on their CMOSIS designed sensors and so have Toshiba and Samsung, I think.

    Digital sensors are probably among the hardest challenges in analogue microcircuit design. So the design of the pixels also matters a lot.

    Best regards
    Erik


    Quote Originally Posted by Guy Mancuso View Post
    The real difference will come down to tonal range and smoother transition because of the bigger sensor. Better said it looks smoother but that gap is getting smaller. They really are Sony sensors . I tested the leaf cmos back , same sensor as the Pentax and it's a great sensor but it's not really night and day, it's close.

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    Re: Take the highest MP count you can get....or

    I know its different, but this reminds me a little of the discussions on film formats years ago, where people cited maths and physics to argue that a 35mm Leica with the right film and lens would outperform 5x4" and therefore there's no point in using a big heavy LF camera. Unfortunately it tended to fall flat on its face in practice (not to mention the other factors at play, which impacted the look of the printed image).

    I agree that the 50MP FF cameras seem to be nudging the practical limit for FF sensors and lenses to really deliver a meaningfully better print in normal use (i.e. regularly used apertures). However, tests show that at commonly used apertures the 5DSR does indeed resolve a little more detail than the D810, even though both have very small pixels (and where the difference in resolution is smaller than 24:42MP). At f16, I would agree that the difference may be gone or hard to see. Certainly the differences between the 5DS and 5DSR are already gone.

    In my experience, 24MP and 36MP can be clearly distinguished in common use (f5.6-f11) and although the difference is not massive or guaranteed. Its more obvious with a very sharp lens at f4 (like the 55mm FE) than with a less sharp lens at f11.

    In answer to what I regard the underlying question to be, 'can you really tell much of a difference between 42MP and 24MP in terms of resolution', the answer is 'yes'. As resolution increases, there are greater demands on technique and also aperture related limitations, but you really have to push all of that hard to the right to force 42MP down to the level of 24MP - far harder than one routinely encounters in normal use.

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    Re: Take the highest MP count you can get....or

    As to the broader question of whether I would always take more MP ...

    Took my A7s2 out for Haloween. Left my A7r2 behind.

    I popped on the insanely great 35/1.4 FE.

    I took many shots at over 50,000 ISO and quite a number at over 100,000 ISO. In some of these I still had to lift the shadows.

    My Slideshow of images to friends and family was a big hit.

    Mostly all color images, I only converted to B&W when the lighting was so garishly mixed that it was impossible to get all the faces looking decent without making a long term project out of it.

    Could the A7r2 do the same thing? No idea really. I wanted easy. I got easy.

    Is 12MP better than 42MP? No idea there either. I do know that the A7s2 does some things with less work than the A7r2. And it makes lovely files.

    So, would I always choose more MP?

    Nope. Apparently not.

    -Bill
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    Re: Take the highest MP count you can get....or

    Yeah, choice is good.

    I have 12, 24, 36 and 42 to choose from.
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    Re: Take the highest MP count you can get....or

    Hi,

    I don't agree that diffraction is kicking in earlier with small pixels. I have made aperture series tests on almost all my cameras and in every case I achieved best result at f/5.6. These cameras were 6MP APS-C, 12MP APS-C, 24MP full frame and P45+.

    What is true is the you loose more MP with small pixels than with large pixels when stopping down, the more you have the more you loose.

    But, there is another axis, and that is sharpening. With good sharpening MTF can be regained but resolution cannot be regained.

    Tim Parkin, the publisher of OnLandscape has looked into this in some detail, and he found that he could get better fine detail from a Nikon D800 he tested at f/22 than from his Sony Alpha 900 at f/8, with adequate sharpening.

    I must say, I have not been able to reproduce his results with the gear I had that time.

    Best regards
    Erik



    Quote Originally Posted by Annna T View Post
    I don't think that the 6+ MP is what sells the camera. The slight IQ difference with respect to the A7r is rather due to the new technology used :

    1) The back side illuminated sensor (BSI).
    2) Then the on sensor PDAF, which is very efficient working in tandem with CDAF.
    3) Add IBIS

    and this body ticks all you need for a good picture (except those needing tracking AF for fast action). Personally I see too many pixels as a draw back for many because it eats storage space like mad and suppose higher processing resources. People are very aware of that.

    Also diffraction kicking in earlier with higher pixels density is nothing new. It has already been abundantly discussed with the Nikon D800 and the A7r (F8 being judged the sweet spot, smaller than that diffraction begun to kick in). It has even been discussed for MFT sensors where you try to keep your lens at F5.6 or wider to avoid it.

    One can use focus stacking to avoid the lack of DOF. Olympus for instance has announced they would implement that feature directly in the body with a firmware update for both the E-M1 and E-M5II. Rumors say that the E-M1II will get 20MB, which could explain why they are working on that feature.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by ErikKaffehr View Post
    Hi,


    But, there is another axis, and that is sharpening. With good sharpening MTF can be regained but resolution cannot be regained.

    Tim Parkin, the publisher of OnLandscape has looked into this in some detail, and he found that he could get better fine detail from a Nikon D800 he tested at f/22 than from his Sony Alpha 900 at f/8, with adequate sharpening.

    I must say, I have not been able to reproduce his results with the gear I had that time.

    Best regards
    Erik
    Then I wish I were a better sharpener ! I have read Bruce Fraser's book on sharpening, not skipping a single page, but I still feel that I don't master it.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Annna T View Post
    Then I wish I were a better sharpener ! I have read Bruce Fraser's book on sharpening, not skipping a single page, but I still feel that I don't master it.
    It's not an easy thing to master, especially since it is very different for every shot.

    I've recently put my trust into OnOne's filter set, which includes a whole parcel of sharpening options. Much more often than not, the defaults work great.

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    Re: Take the highest MP count you can get....or

    The right image looks over-sharpened to me. I see zigzags and jaggies. Sorry.
    With best regards, K-H.

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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by k-hawinkler View Post
    The right image looks over-sharpened to me. I see zigzags and jaggies. Sorry.
    Yes, you are correct. That's what I get for grabbing a random screen capture from Google. But it's the only one I could find, and used it for illustration. This is also a highly compressed .png image from the screen capture, the underlying image already magnified well over 1:1.

    BTW, I never use "progressive" nor go to 100% (and doubtful I'd ever sharpen a portrait). I'd show you what I mean, but this is the wrong thread.
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by uhoh7 View Post
    Guy mentioned if two cameras were on a table he would take the one with the highest MP. He is not alone, for sure.

    But's it's very interesting to hear what the inventor of CMOS sensors has to say on exactly this issue:

    https://youtu.be/JkBh71zZKrM
    That is very interesting. Thank you for the link.

    Now some think when you downsize a 42mp to 24mp the diffraction effects, which are greater at f/11, will magically disappear and the two images will be the same.

    I don't really know, but I would like to find out, because I do shoot a lot of landscapes and I do use f/11 often

    Basically, your question is "which camera will give the sharpest results at f/11 when downsized to 24mp?". The simple answer is the 42mp camera, but the gain will be minimal.

    The full answer is complex, because diffraction is not a hard limit and can be compensated visually a bit (with emphasis on "visually" and "a bit") and also because smaller pixels get the benefit of better color sampling (Bayer array structures are still larger than the diffraction spot).

    The video is more relevant to smart phones and their tiny pixels. The engineer building those and other cameras with similar sensors like P&S or video cameras already know they cannot use small apertures. This is the reason why these cameras use a ND filter internally instead of a diaphragm and usually run their lenses full open all the time. Then, otoh, using a lens full open means one has the full effects of optical aberrations, the lens designer can only do so much.

    In practice, for real life photography, that means the following:

    -if one photographs flat subjects (distant landscape, astronomy, test charts): the optimal aperture for sharpness will be around f/8-f/11 for 24mp and f/5.6-f/8 for 42-50 mp (on a 24x36 sensor size). These are not hard numbers and indeed one can use f/16 with visually sharp images with the help of advanced sharpening techniques.
    -if one wants to use f/11 because of depth of field, the 42mp camera will be a tiny bit sharper on extremely large prints (at least 18"x24" ~ A2 size).
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  46. #46
    Senior Member Annna T's Avatar
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    Re: Take the highest MP count you can get....or

    In the context of this thread, This comparison may be of interest :


    Sony A7R II vs. A7 II - Print Test - Admiring Light

    Admiring light compared the 24MP A7II to the 36MP A7rII at two different print sizes and at F8 or F11.

    He comes to the conclusion that there is a difference but it is subtle with the A7rII showing a little more details. He has downloadable raws and 100% crop of the prints.
    Last edited by Annna T; 6th November 2015 at 07:22.
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Annna T View Post
    In the context of this thread, This comparison may be of interest :


    Sony A7R II vs. A7 II - Print Test - Admiring Light

    Admiring light compared the 24MP A7II to the 36MP A7rII at two different print sizes and at F8 or F11.

    He comes to the conclusion that there is a difference but it is subtle with the A7rII showing a little more details. He has downloadable raws and 100% crop of the orints.
    That the perfect link !
    To resume:
    -if you print A1 or smaller 24mpx is enough
    -If you print larger, with 42mpx you'll start to see a difference, if you print much larger you'll probably see a very big difference.
    -if you want/need to crop a lot you'll also see a big difference.
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  48. #48
    Senior Member ErikKaffehr's Avatar
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    Re: Take the highest MP count you can get....or

    Hi,

    That is sort of what I have seen when i compared my Sony Alpha 99 (24 MP) with my P45+ back (39 MP). No visible difference at A2-size. At A1-size I think there was a visible advantage to the P45+, though.

    If I looked at the images with a loupe, the P45+ had an advantage. So it was not printing that was the limiting factor but my vision. Young people with perfect vision may be able to see differences that I may not.

    Best regards
    Erik



    Quote Originally Posted by daf View Post
    That the perfect link !
    To resume:
    -if you print A1 or smaller 24mpx is enough
    -If you print larger, with 42mpx you'll start to see a difference, if you print much larger you'll probably see a very big difference.
    -if you want/need to crop a lot you'll also see a big difference.

  49. #49
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    Re: Take the highest MP count you can get....or

    Quote Originally Posted by Annna T View Post
    In the context of this thread, This comparison may be of interest :


    Sony A7R II vs. A7 II - Print Test - Admiring Light

    Admiring light compared the 24MP A7II to the 36MP A7rII at two different print sizes and at F8 or F11.

    He comes to the conclusion that there is a difference but it is subtle with the A7rII showing a little more details. He has downloadable raws and 100% crop of the prints.
    Can you give me the link to the raw files? I can't find them anywhere in the article. Thank you.

  50. #50
    Senior Member ErikKaffehr's Avatar
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    Re: Take the highest MP count you can get....or

    Hi,

    On the other hand the images from DPReviews image comparison tool tell a story of cleanness of resolution. Admittedly this is a difficult case, with fine detail having high contrast and photographed under ideal conditions with high resolution lenses.

    Click image for larger version. 

Name:	Screen Shot 2015-11-06 at 23.52.25.jpg 
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ID:	113984

    Interestingly, out of the camera JPEGs don't show colour artefacts.
    Click image for larger version. 

Name:	Screen Shot 2015-11-06 at 23.58.57.jpg 
Views:	24 
Size:	20.7 KB 
ID:	113985

    Best regards
    Erik

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