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Thread: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

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    DT Tech Cam Test - IQ250 vs IQ260 vs IQ280



    Phase One IQ250 Tech Camera Testing

    Go crazy guys. Ask questions. Tear the files apart. Find the good. Find the bad. Let me know what you think of my effective image circle evaluations - they are very much a work in progress.

    I'm going to try my best NOT to be online tonight. Bit burnt out - I worked all weekend and then sat on a tarmac for 3 hours yesterday - the entire time I was working on processing and working up this test.

    We have a few more tests captured, including a great ISO sweep at this same location (I say great because it's a good location for an ISO sweep - lots of dark and light tones, lots of fine detail, lots of color) but it will probably be a few more days before I get to post them as we have an IQ250 Open House in NYC on Wednesday that I have to help prep.
    Last edited by dougpeterson; 10th February 2014 at 16:41.
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Wow. Not looked at the files yet, but clearly a huge amount of work gone into this.

    Thanks Doug.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Doug,
    Fantastic test! Thanks for your time and dedication in finding answers to the questions posed by these new sensors.
    Test looks fantastic. Take a rest. You deserve it.
    Rod
    US Representative, Arca-Swiss International
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    What a great setting! This should be fun.

    Thanks Doug.

    Robb

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I'm just waiting for someone to yell murder and claim false results because you used an an Arca–Swiss ballhead instead of the Cube...
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    On a more serious note, I think the link to the IQ260 and 40HR composite file wrong. It brings up the 35XL composite?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by tjv View Post
    On a more serious note, I think the link to the IQ260 and 40HR composite file wrong. It brings up the 35XL composite?
    Thanks for pointing this out! I've now corrected the link.
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I thought people would be discussing all the details and outcomes of this to death by now… What I want to know is, as a technical camera shooter, forgetting crop factor for a moment, which sensor out of the 250 and 260 looks the most appealing for a tech cam user who already has retrofocus, Rodenstock lenses?

    On LL there is discussion about the 250 having better detail and dynamic range, and the performance with shifts and after LCCs being pretty comparable to the 260 all things considered. What's the consensus here? Being a film shooter and Imacon 949 user at present, I'm not completely sure what to make of these tests. I have suspicions that the 260 would be a better option for me, but can't quite explain what I'm seeing.

    NB: I will add that I can't afford either at the moment, but live in hope. I can see a second hand IQ160 in the mid term, but this gear is a little out of my league.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    The 250 for the most part pretty much blows the 260 away in the tests shown by DT. Especially on the shifts. No CF was used and the 260 would most likely benefit from that but so would the already excellent shadow detail of the 250.

    My take away:

    250 works just like any of the modern Sony sensors does (in 35mm) excellent shadow range and at base iso no loss of details in the shadows.

    260 shows noise in the shifts but the areas that were shifted were almost black on the raw file. The 260 just can't pull up as well as the 250 can. The 250 actually shows the fabric of the wall on the left which also looks very dark on the 250 raw.

    260 has a lot more aliasing and the shifts seem to be a bit softer, but that tends to be the case on underexposed shifting. This subject was extremely challenging.

    The 260 seems to have a lot more stuck pixels even after the dark frame, I was surprised by this. Even after Capture One sets it's defaults and you move the single pixel noise slider to 100% blue stuck pixels remain. This was only a 6 second exposure on the 260 at iso 50.

    To me the 250 show where the future is going, and the only question is with Sony showing no new large MF chips coming (only the 54MP 35mm chip in 2015) will the continue to work on a full frame solution for MF and if so will it be 60MP or 80MP. I have to think that Dalsa is working on something, but I will be frank here, Sony set the bar 2 years ago with the D800, and they just improved it again with the 250. Dalsa will have some work in front of them to get there and as far as I know they don't have a CMOS chip in this market place, I am sure they make CMOS somewhere in their fab plants. But the trick to the Sony chip, is the ability to pull up the details from shadows.

    As a owner of a 260, seeing the results of the 250, I would attempt a move immediately if the crop factor was 1:1. I really have to consider the 1:3 and now am considering upgrading to a 280 so I would have 20MP sensor plus when I need it. In my work the 260 long exposure mode is not needed that much and the 20MP sensor plus should be pretty clean.

    Paul C.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by tjv View Post
    I'm just waiting for someone to yell murder and claim false results because you used an an Arca–Swiss ballhead instead of the Cube...
    Uh yeah, Doug. Could you do these all over again using the Cube?


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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I'm a bit concerned by the uneven pixel vignetting on the green channels of the IQ250, and also how color is affected by the color cast. I'm afraid that if we instead of a colorful ceiling had an overcast sky I we would see uncorrectable color shifts with the IQ250, and we would reduce the usable image circle diameters substantially.

    I think I see that already in Doug's example but it's hard to evaluate as lighting condition could change in the ceiling too. Putting the IQ250 32HR and IQ260 32HR jpeg images side by side makes me think that the IQ250 has some serious color stability problem in shifted areas, due to it's strange angular response.

    For the IQ250 to be a real option for someone with similar shooting style to mine, it must handle ~32mm with 10mm shift, or else I'm it does not go wide enough. I have not been able to see if that is possible or not with maintained color fidelity. I also think that Rodenstock 32mm on a 44x33 sensor is overkill (especially if only a limited part of the image circle is usable), but if you're into a back which is $35K I guess you could shell out $7K for a 32mm lens too.

    This sensor has extremely low read noise, meaning that even if we lose 4 stops in the shifted areas we don't get much noise. However I'm a bit concerned that with so few photons captured that we could lose color fidelity for that reason too. Pushed dark areas are rarely colorful even if they are low noise.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    The results from the 32mm Rod show that a CF would benefit both cameras. I agree that a blue sky shift would be a great test as it's hard enough to balance on the 260 at times when shifting with no clouds.

    I need to look at the 60mm and 40mm Rod shots.

    Torger, did you look at the 40mm so see if has the same color issues you see on the 32mm?

    Paul C

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by Paul2660 View Post
    Torger, did you look at the 40mm so see if has the same color issues you see on the 32mm?
    I looked at it now, and if it's there it surely much smaller. So I don't think I see any color issue on the 40mm, but as said this type of ceiling is more forgiving than an overcast sky.

    What I did see on the 32mm JPEG is demosaicer failure, look just above the "15 mm Rise" label were you see a stitch seam, the topmost image has quite severe mazing and desaturated colors. I think this is due to the different angular responses of the two green channels, and the LCC has not succeeded balancing that out. Possibly with improved LCC algorithm the demosaicing failures and color issues could go away.

    A full-frame CMOS with identical sensor technology like the IQ250 would probably work with the 40mm, and fullframe+40mm is wide enough for many. Let's hope such a back appears soon. If we're lucky they make pixel size a little larger so we get better angular response too. 60 megapixel full-frame CMOS would be nice.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Torger,

    ...look just above the "15 mm Rise" label were you see a stitch seam...
    Why would a seam be visible, given that the back alone moved between captures?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Thanks a lot Doug for that good piece of work.

    Very interesting ! One thing that is definitely not expected (well I suspected it but now there is proof) - the CMOS beats the CCD´s in about any aspect besides that the IQ280 is bigger.
    The IQ260 is a disappointment, grainy, bad shadow details, color noise and actually less quality than the 50 Mpix at 100 ASA though it was shot at 50 ASA. The IQ280 is on 35 ASA and just reaching the level, probably better with more light and less critical brown tones (compliment Doug for this honesty. It is the ultimate test - brown with lowlight shows everything !)

    One hint: the standard settings in C.O. 7.2 are oversharpened (for all 3) and the 260 needed addition of moire.

    This needs to settle down a bit, but in my brain it already forms a BIG question: if the CMOS is SO much better, who will stil buy a CCD ?

    ? ? ?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Torger,

    You have a good eye. I still can't see the stitch line, but on reading you post on the 250 and color sat, I missed that as I didn't look at the finished image or the top images. You are exactly right, the color saturation does fall off, and it's especially noticed on the brown elongated ovals towards the top center.

    What's also is that the stitched 260 image has a strange noise blob on the large partition. The top 1/3 of the partition is actually OK to me, but the lower 2/3's, areas I saw in looking at only the bottom row of images, is way to full of noise. Here is quick shot.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by AreBee View Post
    Why would a seam be visible, given that the back alone moved between captures?
    Even if alignment is perfect a seam can be visible if the two stitched images has different noise levels, ie you see a line where the noise suddenly increases. In this case there is a misalignment though. In the 32HR IQ250 stitched jpeg just below the "15mm Rise" label you see a alignment error (below the "15" before the 60mm IC line, ie just 35 pixels below). I stated incorrectly in my previous post that it was directly above.

    So why is there an alignment error? The camera might have been ever so slightly moved, turning the knobs on the camera body to shift the back can be hard without disturbing the the setup the tiny amount needed to cause a few pixels misalignment.

    A state of the art stitching algorithm can stretch images to make them fit anyway, but I would guess that there is some simpler stitching algorithm used here that don't stretch the images -- and surely we would not want that in this case as we want to pixel peep and see the true pixels the back has captured and not some possibly slightly scaled stretched and rotated image.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by Paul2660 View Post
    Torger,

    You have a good eye. I still can't see the stitch line, but on reading you post on the 250 and color sat, I missed that as I didn't look at the finished image or the top images. You are exactly right, the color saturation does fall off, and it's especially noticed on the brown elongated ovals towards the top center.

    What's also is that the stitched 260 image has a strange noise blob on the large partition. The top 1/3 of the partition is actually OK to me, but the lower 2/3's, areas I saw in looking at only the bottom row of images, is way to full of noise. Here is quick shot.
    I updated in a post above about where the seam is, my first post was misleading I said above instead of below, sorry!

    Concerning the noise blob I think you see a seam between two images. The images overlap a lot so the stitching algorithm don't have to make a straight seam and it has not done it here, so the noisy part is from a noiser image which has been stitched in.

    The question is why so large difference in noise when exposure time has been the same for all images? My guess is that there's some heat problem involved here and the IQ260 is performing much worse than it should, and obviously varying in performance between images. The high noise levels and large amount of hot pixels seen is so surprising I think something is wrong with the back or how it was used in the shoot.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Another issue;

    To make LCC correction the algorithm must have a reference color, ie it must have some point in the picture which is neutral. However with extreme shifts, like in the 30mm upwards shift, there probably is no part of the picture that is neutral for the IQ250, ie the whole picture has color cast. This means that the LCC algorithm cannot know what neutral is and will probably fail to develop the same color balance as the unshifted image.

    The desaturation of the ceiling we see can be due to this.

    The demosaicing failure (mazing) seen in parts of the ceiling is due to that the LCC algorithm fails to balance out the G1/G2 differences that occur due to color cast, this could also be a side effect from that the whole image has color cast.

    I think it could be technically possible to get better IQ250 results than Capture One can do now, but you need a better LCC algorithm.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I am used to seeing the loss of Saturation in extreme shifts, as I believe it's just do to the limit of the lens in question image circle.

    For example the SK35, when shifted on the IQ160 or any 60MP begins to show this at around 9mm of shift and by 12mm the image is basically close to B&W, not to mention the extreme magenta color.

    The corresponding LCC will correct actually quite a bit of the magenta shift, surprisingly so, but it's can't bring back the loss of saturation.

    What you caught in the top of the ceiling shot to me is just the IQ250/32mm Rod limit of rise due to the image circle. The IQ260 does better here, but it's a larger sensor which may account of the differences.

    What I see in the ceiling shot with the IQ250, is no extra detail smearing or noise, (which you can get with the IQ260) just loss of saturation and that can be recovered.

    Your point of a pure blue sky however is very good one, and I don't know how well it would recover as here you are trying to blend back on pure blue and that to me is one of the hardest things to do. If there were clouds in the sky to break up the blue, it would be much easier.

    It would also be interesting to see if the CF makes any difference on this as it would most definitely make the LCC have to work less to recover.

    Paul C.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Okay, I've studied the problem a bit more with my own algorithms and read up a bit on sensor technology. My current theory, and I think it's right this time, is that the desaturation is due to pixel crosstalk. Desaturation is a known artifact of pixel crosstalk.

    What is pixel crosstalk? The angle of incoming light is so low that when it for example passes the the red filter it crosses over to the next pixel and gets registered in the green photodiode. This means that the photon counts between R G B evens out, ie you get desaturation, and slight blurring of details (but the blurring is not very strong, may be less than blurring due to limited lens performance).

    Pixel crosstalk cannot be corrected by LCC, at least not the algorithms seen in current software. So when you see desaturation, it's game over.

    Since the desaturation increases gradually, it is very subjective how usable the IQ250 is with these lenses.

    At this point my opinion is that one should really be careful with IQ250 and wides, it's hard from these tests to know how it's actually performing. What I would do is to make a color checker experiment, first have it in the center and then shoot the same color checker on a strongly shifted lens and see how the colors differ after LCC has been applied. Hmm... I might do this experiment with my Aptus 75 and 35XL...
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    took a quick look at the 250 at Digital Transitions, (courtesy of Doug and Lance) and would comment, from the point of view of a tech camera user:

    the live view is just what you want for composing and setting focus, esp. combined with the IQ quality and image magnification. it does not measure any sort of exposure or provide any sort of exposure information (no histogram, it auto-corrects it's own exposure), so from the point of view of exposure, it is not WYSISYG. this is not a problem, nor is the delay, from my perspective. you do have the ability to live view at whatever aperture you want (unlike GG, which needs to be wide open or is too dim)

    didn't try a tilt/focus experiment, but i have every reason to believe the 250 live view will offer a superior method which may be it's very strongest point

    the crop factor means you will want a still shorter FL lens; the wide angle pixel issue will affect how wide you can go and how much you can shift. one can always go vertical and stitch, (subject to the same limitations)

    high iso is not my bag, but from what examples I saw, 800, 1600 are perfectly fine in print, and you could go more, depending on your own demands.

    have to say, I wanted one
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    There is a post on LL that shows an extreme amount of hot pixels (or something that looks like hot pixels) on the IQ260 shots with NR turned off. I was really shocked to see them! Can anyone comment on if this is normal or not?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Actually noise reduction was on with normal Capture One defaults in images I posted. Even taking single pixel NR to 100% did not get rid of all of them.

    I was a bit surprised by this as I believed the manditory dark frame taken by the camera would have factored them out. Also as exposure was 6 seconds as I recall and that many stuck pixels was a bit excessive.

    The only other CCD camera I worked long exposures with was the P45+ and it was never this bad with stuck pixels.

    What I don't know was was the temp in the room. It may have been warm and caused some excess.

    Comparing it to the 250 either exposure there are no stuck pixels showing I could see.

    Paul C

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by torger View Post
    Hmm... I might do this experiment with my Aptus 75 and 35XL...
    Did a quick one with a color checker in the center and then at the image circle border (90mm) with the 35XL and aptus 75. I used a center filter so the vingetting was essentially zero.

    Similar effect is seen, but to a lesser extent. There's pixel crosstalk which reduces saturation of the colors, and G1/G2 difference that causes demosaicing artifacts (mazing), unless a two-greens-separate algorithm is used like VNG-4 (possible choice in rawtherapee, not in Capture One afaik). I have no screenshots to show now, might do it later if anyone is interested.

    Anyway, I think it's possible to make some sort of correction of this but it's not easy, and Capture One's LCC does not do it for sure.

    When going for an IQ250 I'd suggest that you borrow/rent and do this simple experiment with the widest wide you intend to use:

    Shoot a color checker in the center, turn and shift the camera and shoot the color checker at the image circle border (or any other limit you choose), apply LCC and compare visually. Do you see mazing in the demosaicing? Is the color difference acceptable to you or not?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    one thing i find a bit odd...seems the main feature of the CMOS is the ability to use live view, yet that is primarily of use for tech cameras, not DSLR work, unless tethered, i suppose.
    also the lack of exposure information/histogram in the live view seems an oversight that would have suit the tech camera user quite well.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by jlm View Post
    one thing i find a bit odd...seems the main feature of the CMOS is the ability to use live view, yet that is primarily of use for tech cameras, not DSLR work, unless tethered, i suppose.
    also the lack of exposure information/histogram in the live view seems an oversight that would have suit the tech camera user quite well.
    Good point and may come with a firmware update later on or with the next model.

    Paul C

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by jlm View Post
    one thing i find a bit odd...seems the main feature of the CMOS is the ability to use live view, yet that is primarily of use for tech cameras, not DSLR work, unless tethered, i suppose.
    I shoot a lot of static, planar subjects. I find I can only nail focus with live view. Viewfinder focusing delivers peak detail less than half the time.

    (Actually, what I would really like is a live view mode that goes to 100% at the center and all four corners, all at the same time. I just need a little slice of each to verify that everything is square and in focus. Today I go hunting across the frame to check that focus, which takes ten times as long.)
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    interesting you mention that; as a tech camera tilt user, that would be extremely useful

    listening, Phase?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    And when it comes to the exposure display, how about a view of the histogram that has greater magnification at the highlight/shadow ends - we don't normally care so much about the middle. But make it an option.

    Live View with technical cameras - now that really will be the game changer. I'm using my GG more these days for tilt but dust clean up and taking the back on & off is a bitch.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Actually, when zoomed in 100%, they could add a feature that allows us to do something like double tap one of the four existing buttons (or hold down for 1sec) and that sends you to the corresponding corner of the image. Not as good as seeing all four at once, but it could be implemented with a simple firmware update to all of our existing backs.

    Dave
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I hope Phase will listen to Tech Cam users more. Having two simultaneous selectable magnified screen areas would allow watching near and far focus points as you apply tilt. That would save so much time compared to zooming in, check focus, then out, selecting a new spot, zooming in, tilt, check focus, zoom out, repeat, repeat, repeat. Now that high quality CMOS Live View is becoming a reality, tech camera operation could be greatly simplified and achieve much more accurate results.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by Steve C View Post
    I hope Phase will listen to Tech Cam users more. Having two simultaneous selectable magnified screen areas would allow watching near and far focus points as you apply tilt.
    That would be AWESOME in real life. I'd upgrade to a back that could do that.
    Remember: adventure before dementia!

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

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    These are all great ideas - and things that should be doable in software fairly easily. CMOS really does open up a whole new world for the non-DSLR MFDB user, I just hope the next iteration is more wide-angle friendly. One final thing - again which should be available in software - a real-time focus mask. Imagine tilting the lens and watching the location and extent of the plane / zone of focus in real-time across the whole image. Er, yes please.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I've been using these images to tune the LCC algorithm in Lumariver HDR. I'm not done yet but I've made progress and can report a bit about the IQ250 performance. I use the IQ250 + 32HR raws for the testing.

    This combination has the worst color cast I've seen, and therefore my algorithm needed to be improved to make the best possible out of it.

    The result Doug has succeeded getting is surprisingly good, so good that one can believe that the IQ250 works better than it does for the wides.

    For the 32HR only within the 50mm image circle the back is well-behaved. Then we start to get green channel separation (G1 != G2) and crosstalk. Crosstalk affects color fidelity and green channel separation affects demosaicing precision. In theory the green channel separation should be cancelled out with the LCC, problem is that the main shot and the LCC does not have the same separation, I'd guess because it's a phenomenom that differs depending on exposure, ie the LCC is a bit darker and has less separation, meaning that after LCC has been applied there's still some separation left and demosaicing suffers. The difference between G1 and G2 is about 1/3 stop as most. There are tricks to work around this and I will probably implement that in Lumariver HDR, but the crosstalk is harder to fix. Actually it's impossible but you could hide some of the effect with post-processing techniques. As crosstalk seem to vary over the sensor surface and you can't really know how much crosstalk you have in a certain position it has to become manual guesswork in photoshop.

    Crosstalk means that colors channels are mixed (see attached image) and you get reduced saturation and color precision. If you look at the IQ260 jpeg and compare it to the IQ250 jpeg you'll see that straight ahead the color is quite close between the backs. But if you look above the front window you start to see substantial differences in color. The color does not necessarily look bad, but you have a shift and it's not correct. Further out it's not just a shift the desaturation becomes obvious though.

    There are no raws for the 40HR or 60XL, but based on the JPEGs I'd say that there's large problems there too of this type, and it matches the theory the angles are not much smaller for these than for the 32HR (less retrofocus on the 40 and 60). As soon you start to shift you'll get issues.

    When sensors are designed they are designed with a maximum angle before crosstalk occurs. To avoid crosstalk you put a mask around each pixel, this mask reduces the fill-factor though so you don't want to have it too large. If I remember correctly the KAF-39000 is designed for 39 degrees max angle before crosstalk. The Rodenstock Digaron-W series is probably designed with some sensor design in mind. As retrofocus gives bad properties (more distortion, harder to make sharp) you want as little as possible, only as much to avoid crosstalk for the target sensors. I don't know what design target the Digaron-W series had, but Phase One can probably find out the angle the Sony sensor is designed for and also what the Digaron-W is designed for so it would be quite easy for them to find out what should work per design.

    With post-processing and good LCC algorithms you stretch it a bit more, ie make it work okay despite some crosstalk, but if you invest in a $35K back I think you as a buyer has a right to know which lenses that actually work by design and those which don't.

    As far as I can tell none of the lenses used in Doug's test work well. This sensor requires strong retrofocus lens designs for wide to normal lenses. Still you can get images out of it as this test shows, but tech cameras are intended to excel in image quality and if you start to get color fidelity issues at 5mm shift that's not my definition of high image quality, ie you need both color and resolution to work.

    To make a tech camera friendly CMOS sensor with current manufacturing techniques you need to enlarge pixels and increase the light shield to reduce pixel vignetting and crosstalk (crosstalk is the larger problem here, vignetting is not too bad especially when we have this much DR to dig from and the tests didn't use a center filter). Sony could probably do this quite easily if they wanted. With backside illumination and stacking you can make a sensor where the vertical distance between the photodiode and the color filter is much shorter and thus you can handle much larger angles without pixel vignetting and crosstalk. Sony has these manufacturing techniques but the largest sensor possible to make with this so far is a 1" sensor afaik. It remains to be seen if sensor design will adapt to current tech cam lens design, or if tech cam lens design will adapt to current sensor design.
    Last edited by torger; 18th February 2014 at 01:12.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Fascinating analysis torger.

    It's interesting to note that - to the best of my knowledge - we are still to see a single example of the 23HR with this sensor.

    I'm assuming there's a reason for that, which your analysis may go someway in explaining...

    Kind regards,

    Gerald.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Gerald,

    No conspiracy theory required regarding not having 23HR shots posted. We are more than glad to show which lenses work and which don't. See for instance the 35XL which, frankly, does very poorly with movements on the 250 and 180 and are still shown in the test.

    The reason we don't have a 23HR test posted is more practical: we don't have one in our demo/rental inventory.

    If anyone in the NYC area has one an wants to set up an appoinment I'll be very glad to test.

    I actually think it will hold up fine, including with some minor movement; but only a real world test would say for sure!
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Torger, I really don't agree with the pessimism of your analysis.

    You say "none of the lenses" tested work well with the 250 and I just can't possibly understand how you come to that conclusion. Are there color issues on the outside of the image circle? Yes. But within the usable image circles the color and tonality and detail are really good.

    Perhaps you should 1) request the raws of the 40 and 60 (you say "there are no raws of the 40/60" but in the article I clearly state we have them and are glad to provide them; we only opted not to post hard links to all 100 raws from the test out of concerns we'd overuse our storage account.

    Also, as 99.9% of our customers are using capture one to work up their phase/tech files you might consider doing your analysis there, rather than inventing your own algorithms.

    Of course you're free to come to your own conclusion - that's why I post the raw files and a test this complete.
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Doug,

    you don't need to be so defensive, no criticism intended. I'm very grateful that you've posted this that we can see and use for evaluations. I know I can request the additional files from you (I should have been clearer about that), and I probably will at some point as they will be very good input to algorithms. Just now I haven't, simply because there was no direct link to casually download them and I have not strictly needed more test material yet. I've put in a lot of hours in this analysis so far. When finished my algorithm will most likely outperform Capture One's current which will be good for everyone. Capture One isn't necessarily best at everything you know ;-). Lumariver HDR supports loading a raw file, apply LCC and export as a cooked raw DNG so one can further process in any raw converter with DNG support.

    My analysis is based on what's actually there in the raw files, and compared to other digital backs and what is in their raw files. I see bad behavior as described in my analysis, and that it should primarily affect color fidelity very early on and demosaicing issues further out (mazing).

    To me it's not acceptable that color crosstalk starts occuring with very small shifts, and I have very strong indications that it's happening. Sure you can shoot a scene where color shift and desaturation is less important, but when I buy into a tech camera system I want very high image quality, and that includes color fidelity. I think many other customers also care about color fidelity, tech cameras is more than just wide angle images with sharp corners.

    A test which would make it clearer is to shoot a color checker, first in the center, then further and further out and see how color reproduction change. If "usable image circle" is defined as the image circle where color is the same as in the center (ie no crosstalk) I'm quite sure it will be considerably smaller than the image circles you've stated so far. And that it's exactly the definition I've used in my analysis. You may think it's too strict, that's fine by me, but I would guess there are others that would prefer to use this definition too.

    I think it's wise to be a bit pessimistic until these color issues have been thoroughly investigated. As it's impossible to see what's crosstalk and what's just pixel vignetting in raw analysis of a LCC shot one have to make a color checker test. I have very strong reasons to believe there is crosstalk early on though, as green channel separation and crosstalk happens about the same time on other digital backs. I also see color differences in the jpeg stitches that indicate the same.

    If I was selling these high end systems I would for sure investigate this property. The thing is that a customer may very well make a mistake when buying into it. Detecting a color shift is not too easy especially if you don't know that you should look for it. Say if you rent it a couple of days and you don't know what to look for you may actually miss that the system can't reproduce colors right when shifted, and you buy into this back for doing your interior shots and only a month later or so you realize that color fidelity is not acceptable. I would then be disappointed if the dealer had not informed me.

    You can't just shoot a test scene and "well this looks kind of good, then it must work". The sensor has been designed for accepting a certain max angle before crosstalk occurs, and the lenses have been designed to deliver a certain max angle. If I was buying into this system I would surely want to know from the seller how large image circles that are crosstalk free.

    These library shot gives indications that crosstalk happens early, but a color checker test or other method is required to give an appropriate answer. With your contacts in the industry you can probably get the design targets in terms of angles for both the sensor and lenses too, which is hard for me to get, as they're not available in the public data sheets.

    I'm not here to try to trashtalk the IQ250. But I'm not here to raise it to the skies and try to get people buy it either, I'm just sharing my analysis based on my special expertise so potential buyers know what to look for.

    Quote Originally Posted by dougpeterson View Post
    Torger, I really don't agree with the pessimism of your analysis.

    You say "none of the lenses" tested work well with the 250 and I just can't possibly understand how you come to that conclusion. Are there color issues on the outside of the image circle? Yes. But within the usable image circles the color and tonality and detail are really good.

    Perhaps you should 1) request the raws of the 40 and 60 (you say "there are no raws of the 40/60" but in the article I clearly state we have them and are glad to provide them; we only opted not to post hard links to all 100 raws from the test out of concerns we'd overuse our storage account.

    Also, as 99.9% of our customers are using capture one to work up their phase/tech files you might consider doing your analysis there, rather than inventing your own algorithms.

    Of course you're free to come to your own conclusion - that's why I post the raw files and a test this complete.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Actually, before I started to analyze the IQ250 I didn't even know that pixel crosstalk could be a real problem. And it's true that crosstalk has not been a big problem previously (although I do see it on my Aptus 75 and SK35XL for extreme shifts now when I've learnt what to look for) as CCDs have had quite high critical crosstalk angles with some notable exceptions.

    Problem is that this Sony sensor seems to have a rather low critical crosstalk angle, so crosstalk becomes an issue to look into, and this is a "new" problem which few users are aware of. I don't think many dealers know about it either, as tests would have been devised otherwise if so.

    And perhaps most important -- unlike color casts (comes from angular response variations) crosstalk cannot be corrected with an LCC shot.

    There still is a chance that the crosstalk-free image circle is larger than I think it is, as I cannot say anything for sure based on the current test material. I just have indications.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Torger

    Thanks for the testing and detailed report. I would be interested in your findings on the 260 32mm results if you get time in the future.

    Paul C

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    curious about cross talk and the color effect. how does this work given the Bayer array?

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Torger, you're "discovering" an issue that has been previously discussed on this forum and is even mentioned in the test article I wrote that this thread is about: color fidelity suffers with large movements. This is not new - it was first meaningful with the Aptus II 12 about four years ago and came to broad prominence with the IQ180 when users noticed they could get color casts so severe you couldn't restore high fidelity color.

    I'm not being defensive. We both agree that loss of color fidelity occurs at some point in the movement range and that it occurs earlier in the image circle than with a 260. I'm just saying I've thoroughly evaluated the images and I don't share your pessimism about how early it occurs.

    This was designed to be a worst case scenario full of bright vivid colors which would show the real world impact of any loss of color fidelity. And to my eye they show that the 250, combined with Rodenstock lenses allow a good amount of movement before quality suffers. Less than the 260 for sure, but more than enough to make a 250 a compelling option to consider for a tech camera user. Obviously anyone considering such a system should do their own testing and look out for color fidelity (which is mentioned in my article) as well as light falloff, artifacts, and noise.
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Yes I've known about those color fidelity issues, but I thought this was mainly a dynamic range issue, ie too much signal loss so you can't recover properly. This can also happen, but the IQ250 loses no more than 4 stops of its large dynamic range towards the edge, and that's without center filter. The IQ180 had some micro lens issues too if I remember correctly.

    As far as I can recall the term "pixel crosstalk" or "color crosstalk" was never used so the model I had in my head, and I guess most others too, is that it was all about color casts not becoming too extreme. Color crosstalk is not a difficult term to explain to a layman, it's actually simpler to understand and show in one picture than why color cast occurs. So I find it remarkable that color crosstalk term is not used if dealers have been aware about it for so long. Especially since it's a different phenomenom from color cast and it cannot be corrected with LCC.

    With this sensor we (probably) start to get crosstalk before we've lost even as much as a stop in vignetting and maybe as little as 5mm shift. It's a different mix than before. In other words, the picture looks perfectly okay in terms of sharpness and structure and the LCC shot may look kind of fine, but colors are not right. Knowing that the color channels become mixed makes you look upon the problem in a different way.

    Again, I think it would not be too much to require from a seller of at $35k back to inform potential customers that this sensor is designed with a critical crosstalk angle X, and these XYZ lenses fit this design criteria, these XYZ do not to the IC edge but you can use it up to X mm, and if color fidelity can be compromised you can stretch it a bit more -- but then you are on your own.

    Maybe the P30+ had similar properties, I don't know, but noone really suggested that it would be used with wide angle tech cam lenses. Now there is suggestion that the IQ250 can work, and then I think one can expect a bit better information about this issue. I don't think it's fair to push the testing to the customer, the customer may not be an expert on color fidelity issues, may not even have the best color eyesight, but still want to be able to produce accurate colors from the camera system.

    A gradual increase in noise (caused by corrected color cast) is quite easy to evaluate and find if it's acceptable or not. But a gradual decrease in color accuracy and saturation (caused by crosstalk) is much harder. Therefore I would like to have support from proper targeted tests/measurements concerning those aspects. Maybe I'm alone on that, I don't know, but crosstalk do worry me more than color cast.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by dougpeterson View Post
    Torger, you're "discovering" an issue that has been previously discussed on this forum and is even mentioned in the test article I wrote that this thread is about: color fidelity suffers with large movements. This is not new - it was first meaningful with the Aptus II 12 about four years ago and came to broad prominence with the IQ180 when users noticed they could get color casts so severe you couldn't restore high fidelity color.

    I'm not being defensive. We both agree that loss of color fidelity occurs at some point in the movement range and that it occurs earlier in the image circle than with a 260. I'm just saying I've thoroughly evaluated the images and I don't share your pessimism about how early it occurs.

    This was designed to be a worst case scenario full of bright vivid colors which would show the real world impact of any loss of color fidelity. And to my eye they show that the 250, combined with Rodenstock lenses allow a good amount of movement before quality suffers. Less than the 260 for sure, but more than enough to make a 250 a compelling option to consider for a tech camera user. Obviously anyone considering such a system should do their own testing and look out for color fidelity (which is mentioned in my article) as well as light falloff, artifacts, and noise.
    Notwithstanding the fact that I've been pretty impressed with many aspects of what I've seen so far of the 250, I do think it's worth highlighting the (sure, maybe it's obvious) point re the bolded bit (if it is to be taken verbatim).

    If you're looking to shift to get the top of something in shot (very typical in architectural shots of course), there's a double whammy with the 250.

    You need to shift more than the 260 because of the cropped sensor, and you can't shift as much as you can with the 260.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Quote Originally Posted by gerald.d View Post
    Notwithstanding the fact that I've been pretty impressed with many aspects of what I've seen so far of the 250, I do think it's worth highlighting the (sure, maybe it's obvious) point re the bolded bit (if it is to be taken verbatim).

    If you're looking to shift to get the top of something in shot (very typical in architectural shots of course), there's a double whammy with the 250.

    You need to shift more than the 260 because of the cropped sensor, and you can't shift as much as you can with the 260.
    I was actually meaning to refer to final-subject position. If I wanted to be more generous to the 250 (and be more marketing oriented) I could talk about maximum allowed rise/fall, but as you point out this would be a bit disingenuous as the 250 has to be risen several mm before it's seeing what a 260 would see with no rise. But yes, someone interested in choosing between the two backs for tech cam use will definitely want to download the composite test files which clearly show how far each back can go into a specific area of the subject with a given lens and how much rise/shift that translates to.
    Doug Peterson , Digital Transitions | Email
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    I've looked a bit more on the files, and I've become even more sure that the green channel separation is a crosstalk indicator.

    If you have the sensor in horizontal orientation and shift left, you don't get the same separation of greens. Why? Probably because the sensor has some horizontal wiring between pixel row pairs which photons hit instead of crossing over to the next pixel. If we shift left though this wiring does not become a barrier and we get a more evenly distributed crosstalk, but we still have it of course. Due to this phenomenom you will probably get a slightly different color result depedning on which orientation you have the sensor, and you'll more likely to see demosaicing mazing artifacts if you shift up the sensor horizontally rather than vertically.

    When raw analyzing the LCC shots of the IQ260 from the 32HR there's no significant separation of greens anywere in the image, from which I assume that there's no crosstalk and thus likely that the whole image surface has proper color reproduction, which also seems reasonable as the Digaron-W 32 was designed when 6um CCD sensors existed on the market.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Oh, while out running I figured out the mystery why the green separation is different on the LCC shot compared to the main image. This is because it's a directional crosstalk phenomenom.

    For exampe we may have leaks from blue to green and green to red, but not as much from green to blue and red to green, depending on the direction of the shift and orientation of the sensor. This means that a particular shift and sensor orientation will have a particular crosstalk, and that crosstalk will cause larger effect for some colors and smaller for others.

    The LCC shot is made with some light source diffused through a white card, which will lead to one particular crosstalk distribution which is different from if the sensor sees say a clear blue color in the same position.

    Maybe my explanation is not too easy to follow, but anyway the result is that depending on shift and orientation of the sensor the color fidelity will be affected in different ways. If you're lucky the scene you're shooting won't contain the colors that are affected the most.

    Due to the complexity of the effects of crosstalk, ie that you can get different results depending on scene content and composition, it's not wise to draw conclusions that "it's good enough" from one test. The right way is of course to not use the sensor with shifts that introduce crosstalk.

    I only need to look at LCC raw files to make a good estimate where crosstalk begins (which is where greens start to separate), and for the IQ250 with 32HR it starts around 40mm IC, ie the corners of the unshifted image is slighthly affected. You need certain strength before color differences start become visible (and as said, how colors are affected is hard to predict), but you need to be inside that to be safe.

    So if color fidelity is important to you, the 32HR + IQ250 is not a great combination for you. The only reason I see the IQ250 to be suggested for this type of combination is live view. If the IQ250 did not have live view noone would think it would be a good idea to push crosstalk limits and hope for the best.

    For professionals that need consistent results with tech wides the IQ260 must still be the recommendation over the IQ250 at all times.

    I've attached an image that maybe helps to show my concern about the color fidelity. It shows how similar IQ250 and IQ260 are in the center of the image (as they should be assuming a sane profile has been used), and how quickly the colors start to separate quite significantly. It might partly be a white balance issue in the processing (it's from the example jpegs, not my own processing), but turning a green dress into blue without an otherwise severe cast is likely not a white balance issue alone, and there is documented crosstalk there, as I also show in a magnification of the green channels directly from the raw file which shows the horizontal lines due to separation (ie a crosstalk artifact).

    The dress color change from green to blue in the painting may look extreme, but I don't think it is from a crosstalk perspective. Muted colors (ie a high and similar content from all three RGB channels) is more likely to change hue due to a crosstalk phenomenom (as you only need a small change to make the balance tip over to a different hue) than saturated colors which probably is just going to look a bit desaturated. But it will as said depend on the sensor orientation too as that decides in which direction the crosstalk flows. If the same painting had been shot with the sensor in vertical position I'm quite sure the color would be yet another. Probably different if you attach the back horizontal but upside down too.

    Maybe I am the last person to know about this phenomenom and this is just old news. But as the last one I can sure tell you that if I had tested the system with the knowledge I had say one year ago, I could have missed this, you need to know that you should look for color, and not just be blinded by the fantastic sharpness and lack of noise, and the liveview of course. I hope the potential buyers that rent for testing know more about crosstalk than I did.
    Last edited by torger; 18th February 2014 at 13:47.

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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Till your last post it was pretty clear to me, that you are some kind of crazy scientist that lost his mind in numbers and other dimensions. It wasn't easy for me to get any content out of your first gazillion word posting which seemed to never had an end... and I was scared that I would end up in an alternative timeline, if I would continue reading your posts. So I stopped.

    But that last crop cleared things up a lot for me.
    A picture... worth a thousand words.

    Thanks Torger!

    To me, this looks like big bad news.
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    Re: DT Tech Cam Test - IQ250 vs IQ260 vs IQ280

    Here's another picture which shows where I took out the crop of the painting (the green rectangle). Note that it's just outside the unshifted frame. I reattached the original crop comparison image for reference.

    The picture also shows the whole IQ250 and IQ260 32HR stitched images side by side so you can see that in the center area of the lens the color rendition is very similar, and outside you start to get quite different colors, due to crosstalk occurring on the IQ250, while the IQ260 provides the whole image circle free from crosstalk.

    Note how quickly the IQ250 color fidelity fails vertically while it handles quite okay sideways, this is extra clear on the right side of the image where you get a sudden color shift/desaturation in the large painting on the right wall, almost a sharp edge. This is because the different crosstalk behaviour vertically vs horizontally on the sensor. I'm not sure if horizontal crosstalk is less or if it's just more evenly distributed hurting those particular colors in the image less. More thorough testing in lab conditions would be required to figure that out. I think though that if we put a color checker just outside to the left or right of the unshifted frame we would see a color shift, just not as large as we do vertically.

    Currently the DT page states 80mm usable image circle for color images for the IQ250/32HR combination. I do not agree with that. From my test results presented here I'd say that the guaranteed circle for color fidelity is no more than 40mm (supported by my measurements of crosstalk in the LCC shot), and the area with reasonable amount of crosstalk to only produce slight color shifts is not a circle, it's an oval related to the sensor orientation, which is about ~40mm high and ~55mm wide for horizontal orientation. You're free to make your own interpretations.

    I hope I've presented enough material so any user trying out this combination or others know what to look out for.
    Last edited by torger; 19th February 2014 at 01:18.

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