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Thread: sensor size question

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    Senior Member danlindberg's Avatar
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    sensor size question

    Although I am truly satisfied with my 'baby' DB Aptus II 5, ofcourse I cannot help but looking at the latest of the latest....(P1 - IQ)
    However, there is one factor that keeps me hesitating towards the full format sensors and that is the amount of shift possible with any given lens! Isn't there anybody out there that actually chose an IQ140 33x44 sensor over the big guns because of this?
    Yes, ofcourse I realise that most (I would) would need an extra lens (HR23) which means the total cost would be roughly the same as to have chosen an IQ160 instead of the 140. So it is not really about saving money.

    I also realise ofcourse that considerably more mp is a good thing, BUT, in my world 40mp would be more than enough, today my tiny 22mp is bringing my bread to the table and not once has a client commented on filesize.

    Bottomline question is: Why is the larger sensorsize so attractive? What is so much better that you are willing to give up movements?
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    Senior Member yaya's Avatar
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    Re: sensor size question

    Larger sensor means wider AOV for a given focal length plus the DOF becomes narrower at a given aperture

    If you need movement to increase the image area (stitching) then the larger chip gives you some of that already

    If you need movements like rise/ fall to correct perspectives then in reality your Aptus-II 5 (or the 7) will give you more of that because of the larger pixels (9 or 7.2 respectively) and the resistance to severe colour casts and falloff at the edges, compared to the 40MP (6) backs

    Saying that, Graham Welland shoots on a tech camera with an IQ140 quite happily I think:-)
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    Re: sensor size question

    Dan,
    I just opted for the IQ140 to use with a tech camera. Of course, budget reasons were a big factor, but in reality I don't need the extra resolution. The only limitations (for me) are: 1) less ability to crop the file later on 2) not seeing a full
    frame in my DF viewfinder, which is quite annoying to me. But this is eliminated with tech camera use. And 3) not being able to get the full wide angle benefit of the wider lenses. So since the 35 becomes equivalent to a 46, I plan to eventually add an SK 24 which is considerably less expensive than the other wide lenses. There's still some room for minimal shift with the 140 sensor, and the crop factor helps with the edges. The downside is that lens is not too good if you move to a 160 sensor. and is probably useless with the 180.

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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: sensor size question

    I think that Yair and Gary sum up the aspects and advantages (or at least lack of disadvantages) of the smaller sensors very well for technical camera use. There are definitely less headaches with lens image circles, LCC casts (and in the past there were image banding issues too on superwides/small pixels) than you get as the sensor size increases and pixel pitch decreases. Be careful about what you wish for ..

    Btw, I actually chose to get an IQ160 in the end vs IQ140 but for reasons unrelated to image quality or capture capabilities, especially as they pertained to a technical camera. I do think that the IQ series capabilities for image assessment in the field are a game changer vs the P+. I love focus mask for example. That said, the Leaf backs also are outstanding for technical camera use too. Overall the IQxxx is just plain cool but that's not what you're asking about! Looking at it rationally just as it pertains to technical camera use I know that I personally would have been just as happy with an IQ140 vs IQ160/IQ180. The extra resolution is great but not the overriding factor for me - for others it is no doubt much more important. That said, I'm not going to give it back either

    One thing I would look at carefully is the sensor pitch and how that affects your DoF. 9um is a lot more forgiving than 6um or 5.2um for example.
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    Re: sensor size question

    The larger the sensor, the more signal one records (compared to a smaller sensor). More signal means a better signal-to-noise (SNR) ratio. When recording digital data nothing beats SNR. As the SNR increases the bits used to digitize the noise decreases. In the end, a larger sensor has more dynamic range.

    While the following article by Emil Martinec discusses the theory and shows empirical results for DSLRs, the principles regarding sensor size are relevant.

    Noise, Dynamic Range and Bit Depth in Digital SLRs

    The Big Pixels VS Small Pixels section is most relevant to this thread.

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    Re: sensor size question

    When comparing the Phase sensors, the pixel size of the p40+, p60+, IQ140, and IQ160 are all the same. In fact, the sensors of those backs are all identical. The smaller sensors are literally just smaller in physical dimensions than the full frame versions. So if you stiched with a p40 or IQ140, you could end up with a file and image with the same image quality, dynamic range, etc. as the larger backs.
    The IQ180 is a different sensor.

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    Senior Member Graham Mitchell's Avatar
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    Re: sensor size question

    My own reasons:

    - my widest lens (40mm) is now equivalent to a 27.7mm lens on 35mm. With my 36x48mm sensor it was equivalent to 30mm. If and when DHW release the 35mm lens, that will now be equivalent to 24mm.

    - I mostly use manual focus, and the larger sensor means that a larger proportion of the viewfinder is now active. Another way of looking at it is that my view has now been magnified by 8%, making manual focus a little easier.

    - the cropped sensor and viewfinder were just untidy.

    - I wanted to be able to achieve shallower DOF when using the lenses wide open.

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    Senior Member danlindberg's Avatar
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    Re: sensor size question

    AAArgh I just wrote a longish post and lost it while submitting it.....

    Must leave, but thanks for your replies. Interesting.

    If I may put a followup question from a architectural photographers point of view - if you could choose any DB and it would be used exclusively on a tech cam with as much movements as possible, which one would you pick?
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    Re: sensor size question

    Dan, If your concerns are around the edge cast problems on the larger sensors, I think the 60mp sensors are worth considering. Well proven. I concur with Graham, no real game changer in terms of image quality. IQ backs are all about usability.

    In case, what you're aiming at here is that more shift means you can get more of the subject in frame before it becomes necessary to point the camera upwards. As the image circle is fixed in size, the larger sensor gives more choice, to shift more and crop off the vignetted corners or even use context aware fill/cloning to get rid of them. In fact it was a compromise you might be willing to make even on film, ultimate sharpness may be compromised on some lens designs by tilting the lens from the film plane.

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    Re: sensor size question

    Same resolution, different size sensor -> different diffraction.

    Larger sensors can suffer more closed apertures, at the same diffraction.

    This goes in the opposite direction from DOF, but is stronger, i.e. Overall sharpness can be better with a larger sensor.

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    Senior Member danlindberg's Avatar
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    Re: sensor size question

    yes, wback, I think the IQ 160 might be the best choice all things considered for a tech cam. I am not around the corner to upgrade so I'll keep on reading on progress

    Interesting shlomi, so diffraction is visible 'sooner' with larger sensors. I did not know!
    Last edited by danlindberg; 9th October 2011 at 11:44. Reason: wrong wording
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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: sensor size question

    Dan,

    If you are looking at the IQ160 I'd also recommend taking the opportunity to try an Aptus II 10 (or DM 56 as it's now called). For technical camera use it's also a very very able back as far as the UI is concerned. I was very impressed with the latest version compared to my own IQ160 this week. The sensor aspect ratios a little different but that may or not concern you if glutting.
    Remember: adventure before dementia!

    As Oscar Wilde said, "my tastes are simple, I only like the best"

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    Re: sensor size question

    Yair, I am showing off my ignorance here, but I am trying to understand why does a bigger sensor produce a shallower depth of field with the same lens and camera and thus focal distance to capture plane?
    Last edited by arionelli; 10th October 2011 at 04:51. Reason: clarity
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    Re: sensor size question

    There are a lot of moving parts here.

    The focal length of the lens is a factor in DoF, the format has nothing to do with DoF. However if you use a 50mm lens on small format, to achieve the same view you'd need roughly an 70-80mm lens on MF and a 150mm lens on 4x5 format. Therefore to have a normal perspective would actually cause a drop in DoF. This may be the confusing factor here is that the focal length must increase as the format size increases, thus limiting DoF.

    Secondly a smaller dot pitch on the sensor would require a smaller CoC for max resolving power. What you will find is that you wish to have a smaller CoC with finer pixel dot pitch. So, for example on an IQ160 with a 6u dot pitch would use the same CoC as the smaller 56MP sensor, which also has a 6u dot pitch. Whereas the IQ180 (which is the same size as the IQ160 roughly) has a smaller CoC and therefore to extract maximum resolution, would require a smaller aperture, thus creating a smaller DoF.

    In summary a IQ180 vs IQ160 would require smaller aperture, thus have less DoF for the same size sensor (to extract maximum resolution)!!

    Paul

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    Senior Member yaya's Avatar
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    Re: sensor size question

    Quote Originally Posted by arionelli View Post
    Yair, I am showing off my ignorance here, but I am trying to understand why does a bigger sensor produce a shallower depth of field with the same lens and camera and thus focal distance to capture plane?
    Imagine you're shooting table top with an 80mm lens on a 645 camera and a large sensor like the Aptus-II 12 (41x54mm). You move the camera back/ forth until you get all the subjects on the table into the frame

    Let's say that your desired DOF (or depth of focus) is now achieved at f11

    You then change the back to one with a smaller sensor, say an Aptus-II 8 (44x33mm). You are not changing the lens and you're not changing the aperture

    If you want to get the same composition and angle of view, you will have to move the camera BACKWARDS. Because you have not changed the aperture and/ or the lens's focal length, you are "compressing" the scene and thus increasing the DOF

    In other words, because the distance between the scene and the film plane is increased but you're viewing it through the same glass/ hole combination, there is going to be a deeper part of the scene that will fall into focus

    I hope this makes sense?

    If I get a chance I'll post some images that demonstrate it

    Cheers

    yair
    Last edited by yaya; 10th October 2011 at 07:41.
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    Re: sensor size question

    Excellent way to describe it Yair!

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    Re: sensor size question

    Quote Originally Posted by wentbackward View Post
    Excellent way to describe it Yair!
    Agreed, perfect way to look at it. And using that as an example, if I could step further back from my typical landscape infinity to fill the crop frame, I might have considered one instead of a full-frame sensor!
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    Re: sensor size question

    Thank you, Paul and Yair. Yes, that is very well understood. One very technical, the other practical.

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    Re: sensor size question

    Does anyone know if the IQ140/Credo 40 uses a sensor with microlenses, which would make it unsuitable for heav shifting on a tech cam?

    thanks,

    geb

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    Re: sensor size question

    Quote Originally Posted by danlindberg View Post
    If I may put a followup question from a architectural photographers point of view - if you could choose any DB and it would be used exclusively on a tech cam with as much movements as possible, which one would you pick?
    I'm having my eyes on Hasselblad CFV-50. 48x36mm 50 megapixels I think seems to be the ultimate tradeoff in terms of maximizing resolution while keeping movement possibilities. However the Kodak sensors have some color cast and not as good color reproduction and need special synching so I'm not sure anyway. An IQ160 is probably "the best" for tech cameras today I think although movements will be a bit limited.

    I'm myself very pleased with my Aptus 75, 33 megapixels 48x36mm, very little color cast and works perfectly with normal synch cable. I'd love to see a 50 megapixel 36x48mm Dalsa-chip for tech cameras, I think 54x41mm reduces movements a bit too much on the current wides.

    With more than 50 megapixels it becomes so hard to utilize all resolution that it may take out some of the enjoyment. I'm not so fond in focus stacking, I rather use some tilt and a small aperture but I realize if you have 80 megapixels you'd be tempted to stack a lot.

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    Re: sensor size question

    Dan, its a bit different for myself as I shoot a P65+ so the sensors and IQ of the new IQ/Credo's backs are basically the same but at this moment in time I personally would have a hard time justifying investing a large lump of money into an IQ or Credo when considering the leaps and bounds CMOS technology has jumped in the new Nikon.

    I don't know if its possible for MF companies to adopts CMOS yet but it has to happen at some point as the advantages of CCD are getting smaller and smaller, year on year.

    I love my P65+ on the Arca and wouldn't swap it for any 35mm system but upgrading for funky features alone on the IQ's/Credos is just not worth it IMO. Obviously for you, the upgrade in IQ from the Aptus to an IQ140/160 would be quite different image quality wise but if your clients love your work and its just for the toys I'd be tempted to wait and see what develops in MF land. I personally think HB are up to something and wouldn't be surprise if they are first to the finish post with new MF chip technology.

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    Senior Member danlindberg's Avatar
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    Re: sensor size question

    This is a very old thread that has come alive.

    My position today is that I am totally happy with my Aptus II 5. I am getting very good results for what I and my clients need. Ofcourse, I would love to be able to shoot a modern Credo, but in all honesty, it isn't necessary.

    Photokina will be incredibly interesting.
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    Re: sensor size question

    heh, I didn't notice the thread was old

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    Re: sensor size question

    I can run a test today . The IQ 160 I just sold for the IQ 140 I could get a safe rise/fall movement with the Roadie 28 on the 160 of about 7mm . Now I will get more movement on the IQ 140 which I'm thinking will be 10mm but I need to move back to equal the same focal length the 160 had which is 18mm in 35 world compared to 22mm on the iq 140. All things being equal and I could move back than the movement advantage will go to the 140.

    I've been meaning try this but been busy. I shot 2 frames on this back , need to go break her in. LOL

    This was one reason I was not to unhappy to drop down to the crop of the 140 since it really don't matter much on a tech cam except if you can't move than obviously the FF would be better and you do lose some look with wide angles .
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    Re: sensor size question

    Quote Originally Posted by danlindberg View Post
    ...I also realise ofcourse that considerably more mp is a good thing...
    Why? Your clients don't notice it. You have more than enough detail as it is. The larger images bring larger file sizes which means more storage and more processing power. But with a doubling of pixels, you only get a 40% increase in resolution and a doubling of file size.

    I would go with a larger sensor for how it impacts things like DoF and being able to use lenses at lower frequencies so I can get better contrast/MTF, but not worry about how pixel pitch. The subtle impacts on the image because of sensor size would be the only reason for me to jump--but the darn file sizes are a turn off. Now, a 40MP 6x4.5 sensor would be great.

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    Re: sensor size question

    BTW, just because you can move a smaller sensor back further than a larger one, does not mean you actually end up with more movement--it will end up have the same apparent field of view if you are stitching. The sensor is not a limit to movements, the lens image circle (and camera) is.

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    Senior Member danlindberg's Avatar
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    Re: sensor size question

    Shashin, it's an old thread/question (I've learnt a thing or two since then). I'm happy with my workhorse Aptus II 5 and I am not looking for any upgrade.
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    Administrator, Instructor Guy Mancuso's Avatar
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    Re: sensor size question

    Im not so sure about that. I have limits on the lens movement on how far it will go the Roadies have disks in them that cut you off at a certain point. Maximum I could rise the 28mm is 7mm before the disk kicks in on a 160 Full frame ( it shows on the image) on a IQ 140 that will not show until about 10 or 11mm ( i need to make sure of this too). Now if i pull the camera back to the same focal length as the 160 it should give me net overall more rise. Im at the same focal length but I get more rise
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