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IQ3 100MP technical camera tests: color cast, mazing artifact, tiling issue, DR etc

Let's continue with the mazing artifact tests for the 40HR. The worst part has shifted a little bit upwards for this lens. It is now between the blue cast region and the magenta cast region as shown below.

Mazing artifact is about to start at +15mm shift and happens for +18mm shift. So my advice is to stay within 15mm range of this lens when you shift it along the shorter edge of the sensor.

14.JPG

16.JPG
 

torger

Active member
It should be said that C1's demosaicer is very robust, you need to get into pretty extreme amounts of crosstalk for it to start mazing. If you use a plain DCB demosaicer you practically have a crosstalk detector, it starts mazing with only a few percent of crosstalk.

That it happens more easily in certain lights is expected, to trigger it more easily you should have some light that is a lot stronger in one CFA filter (red blue or green) than the others as the crosstalk will be more evident then. If light matches up on red/green/blue then nothing happens if there's crosstalk. This makes the effect color and light dependent meaning that I personally don't like to play with high levels of crosstalk as it can look fine in some circumstances and then problems can jump at you when you have some particular saturated color in the frame or there some particular light.

That said if the IQ3100 really does have less issues than the IQ250 then it looks pretty good to get down to an acceptable level for many/most people.

You almost 100% certain can't read 16 bit IIQ files correctly in rawdigger, so forget that until someone reverse engineers the format (probably some minor extension).
 

torger

Active member
15mm shift is good for the 40mm, I'd be quite happy with that. However as I know mazing means pretty gross amounts of crosstalk I'd like to do more thorough tests on color fidelity before accepting 15mm a within the okay range for safe high end image making.

I guess you can say that mazing is the "stop range" where the image is truly ruined, but you have a zone before that where you have color fidelity significantly affected by crosstalk and how visible that is will be a lot "it depends", plus how good eyes you (or your clients) have.
 
15mm shift is good for the 40mm, I'd be quite happy with that. However as I know mazing means pretty gross amounts of crosstalk I'd like to do more thorough tests on color fidelity before accepting 15mm a within the okay range for safe high end image making.

I guess you can say that mazing is the "stop range" where the image is truly ruined, but you have a zone before that where you have color fidelity significantly affected by crosstalk and how visible that is will be a lot "it depends", plus how good eyes you (or your clients) have.
Color is something very personal so...

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jagsiva

Active member
Strange purple glow in the blacks, even on the image above. Also the neutral shades look a little green. Hopefully both related to the LCC bug
 
Now, the show time of the Sony CMOS sensor - dynamic range under long exposure!

First of all, it was lucky that I bracketed a bit for the long exposure shots so I have had just the right parameters for analysis!

Indeed, when Phase One wraps up the ISO settings (along with the dedicated long exposure mode for the IQ380 and IQ260) things can get very confusing - what is the real native ISO?

Instead of starting another long debate here, I employ a simpler method to try to minimize dispute:

I shoot each back at the lowest possible ISO (where for the IQ380 it is ISO 200 in the dedicated long exposure mode). I use the Lee Big Stopper. I shoot at the same aperture.

What I have found is that regardless of the difference of ISO among these three backs, indeed the same exposure time gave me about the same highlight headroom! See proof below: I converted all RAW files by Capture One v9.0.2 then checked the mean value of the fixed sky region. These are about the same.

Then I used the following settings for each image: I match the exposure of each image, then use the "Pick white balance tool" on the same spot, then push +100 shadow and pull +100 highlight, then disable noise reduction.

Note that for these two CMOS backs when I took the long exposure shot I disabled darkframe noise reduction by setting "Camera Mode" to "Aerial". This is indeed a key feature for landscape photography so to avoid waiting for the noise reduction countdown! Then for these three backs I moved the slider of "Single Pixel" to 1 (out of 100).

Now we look into the shadow: boom! You know what I'm talking about and why I am a fan of the Sony CMOS sensor! It is really the king in this kind of shootings! This is what I am willing to sacrifice other things for.

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20.JPG
 

torger

Active member
This can turn out maximum painful for me, that is it will work, but on my lower limit of acceptable shift range plus having to play in the uncertainty zone concerning color fidelity. Aaaaaaaaaargh I could be sleepless for less.

It feels like "We can improve these five things but you need to sacrifice these three." At some point the "why am I messing with this stuff" feeling will get too large and it's SLR or even film for me...
 
By shooting the BClaff DR test chart, I have found that ISO 50 and ISO 100 are indeed the same for the IQ3100, i.e. ISO 50 behaves as an extended ISO (just like ISO 32 for Nikon D810).

Proof is attached below: just read the numbers. These dng files are converted by Capture One v9.0.2 so there is no blame for RawDigger to take.

22.JPG
 

yatlee

Member
Thanks for the great overview. I also notice the green cast on the LLC and hope the new version will fix it.

A question for you; you mentioned - "Note that for these two CMOS backs when I took the long exposure shot I disabled darkframe noise reduction by setting "Camera Mode" to "Aerial". This is indeed a key feature for landscape photography so to avoid waiting for the noise reduction countdown!" Any draw back by not doing the noise reduction countdown?

Top IQ3100, bottom IQ260
 

Attachments

Thanks for the great overview. I also notice the green cast on the LLC and hope the new version will fix it.

A question for you; you mentioned - "Note that for these two CMOS backs when I took the long exposure shot I disabled darkframe noise reduction by setting "Camera Mode" to "Aerial". This is indeed a key feature for landscape photography so to avoid waiting for the noise reduction countdown!" Any draw back by not doing the noise reduction countdown?

Top IQ3100, bottom IQ260
You could use Capture One v9.0.1 to remove (perhaps almost completely) the color cast and I guess the 32HR will look very nice. ;)

By not doing the noise reduction countdown, a CCD back (e.g. IQ260 or IQ380) will suffer from major degradation of image quality depending on the length of the exposure time. On the other hand, a CMOS back (e.g. IQ250 or IQ3100) will only introduce some hot pixels, which can be easily fixed when you move the slider of "Single Pixel" to 1 (out of 100) without impact of sharpness or details.
 
According to my friend from Sony's sensor department, the Phase One IQ3 100MP (IQ3100) is not based on the IMX161 technology of the IQ250. It is not based on the IMX251 technology (A7R-II) either. It is not a BSI design. The part number of the sensor used in the IQ3100 is something like IMX3??, which is still under NDA (Phase One exclusive? I doubt).
 

torger

Active member
According to my friend from Sony's sensor department, the Phase One IQ3 100MP (IQ3100) is not based on the IMX161 technology of the IQ250. It is not based on the IMX251 technology (A7R-II) either. It is not a BSI design. The part number of the sensor used in the IQ3100 is something like IMX3??, which is still under NDA (Phase One exclusive? I doubt).
The behavior does look a bit different than the others, so indeed it looks like something new. It's a nice surprise that something new can be introduced at the largest size first. Looks like Sony has taken the next little step in DR here first for example?
 

torger

Active member
There's no obvious color issues in the 15mm shifted 40HR shot, and this is very promising. It's strange though that they've made the IQ3100 so different in saturation than the IQ380, it shouldn't be necessary. I'd like to analyze some raws myself at some point, preferably the 14 bit ones so I don't need to mess with the new format.
 

jagsiva

Active member
There's no obvious color issues in the 15mm shifted 40HR shot, and this is very promising. It's strange though that they've made the IQ3100 so different in saturation than the IQ380, it shouldn't be necessary. I'd like to analyze some raws myself at some point, preferably the 14 bit ones so I don't need to mess with the new format.

Anders,

If you look at post #24 above, specifically at the wall above and below both sets of windows, the colour are quite different. The left set have a green shading, and the right set have a purple shading when compared to the IQ180 file.
 
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Astralark

New member
CA issue for 100MP is because that lens have CA measured in microns. In 80MP sensors, the pixel size is larger than 100MP one. For example, a lens have 12um CA will use 2 pixels to show residual color in 80MP back but takes 3-4 pixels to show in 100MP back.
 

torger

Active member
Anders,

If you look at post #24 above, specifically at the wall above and below both sets of windows, the colour are quite different. The left set have a green shading, and the right set have a purple shading when compared to the IQ180 file.
I noted the differences and think they're surprisingly large. However it seems like the IQ3100 is overall more saturated, perhaps a bit oversaturated, but I'm not able to spot any obvious uniformity differences. The walls above and below the top left windows are indeed of different color which is suspicious (especially the duller gray above window has a typical crosstalk-desaturation look to it), but as its the same on the IQ380 I'm guessing it's an actual color difference of the wall, unless the 380 has similar issues.

Likewise it can be seen as suspicious that the brick wall is less saturated close to the upper edge, but I'm assuming that's a lighting/glare thing.

I know from previous analysis that the 80MP sensor has more issues with the rodies than the 60MP and I always thought the 60MP is a better choice for tech cam users that like to shift, but I never had a look on crosstalk-desaturation issues, so unfortunately I don't know if the IQ380 color can be trusted or not, but I would be surprised if it wouldn't handle 15mm shift of the 40mm.

On the other hand if you look at post #21 it's shown that the IQ3100 should have some issues at 15mm shift, it's a meaner lighting condition in the #21 test but there should be some effect there.

Say if it really is the case that the brick should be uniform saturation and the concrete(?) above and below the window should be the same color than the performance shown in #24 would not be acceptable to me personally, even if it obviously works as an image. So the color stability is something I'd like to have further investigated.

The scary thing about crosstalk is that its effects can easily pass undetected in the enthusiasm for lots of other CMOS advantages, meaning that we start compromising tonality and color fidelity -- that is one of the classic key selling points for medium format digital. It can be fully acceptable in many use cases but it is one aspect that at least I would want to fully understand before I would invest in this type of gear.
 
CA issue for 100MP is because that lens have CA measured in microns. In 80MP sensors, the pixel size is larger than 100MP one. For example, a lens have 12um CA will use 2 pixels to show residual color in 80MP back but takes 3-4 pixels to show in 100MP back.
I have down-sampled the IQ3100 image to 80MP but it still has that purple glow there.

34.JPG
 

torger

Active member
I don't know what the purple glow is, but as it's in direct connection to a bright edge on that CCTV I'm thinking that it's some sort of internal reflection, could it be a reflection in the sensor glass or something? Just speculating. If it would have been normal CA of the lens I would have expected it to show more on other edges too, and of course be seen on the IQ380...
 

ErikKaffehr

Well-known member
Hi,

Diglloyd has observed something similar on the Leica S2. He found it was caused by insufficient filtering of either IR or UV, I don't recall. He discovered it was not visible on subjects illuminated bye LED-light, and started experimenting with IR and UV cut of filters.

Best regards
Erik

I have down-sampled the IQ3100 image to 80MP but it still has that purple glow there.

View attachment 115607
 

jagsiva

Active member
Hi,

Diglloyd has observed something similar on the Leica S2. He found it was caused by insufficient filtering of either IR or UV, I don't recall. He discovered it was not visible on subjects illuminated bye LED-light, and started experimenting with IR and UV cut of filters.

Best regards
Erik
Could be, the blacks going purplish is a bit like the M8 issue IR cut off issue.
 
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