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Author Topic: A small comparison of colour accuracy, P45+ vs. Sony SLT99, C1 vs. LR5.3  (Read 2338 times)
Fine_Art
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« Reply #20 on: February 25, 2014, 05:23:31 PM »
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isn't IT8 way too glossy target to use (and wasn't that the reason why Colorchecker DC failed) ?

I don't know. I would think IT8 is fine in diffuse, high CRI light. I do know Silverfast says it is not designed for DSLR calibration. I settled on the idea of the IT8 as a gamut test more that a color test for DSLRs.



Imaging Resource has ISO100 raws for a huge number of cameras with a color checker in the shot (still life series). If there is a problem with a raw converter is should be easy to test.

C1 should be designed for MFDB compatibility so it is very surprising if they fail there.
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ErikKaffehr
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« Reply #21 on: February 26, 2014, 09:04:50 AM »
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Hi,

This is D800, Capture One using linear curve. LR 5 significantly more exact.

DPReview has an IQ180 test shot they have as reference shot. I have tested the CC with both C1 and LR5. C1 was more accurate.

From all tests I have done I would say that Capture One is pretty accurate on the Phase One shots I have tested with the linear curve, but less accurate on DSLRs. LR is easy to calibrate to each camera.

The differences are not really large. What I can see that saying that C1 and MFDBs are more accurate seems to be a blanket statement without much substance. It is very possible that they yield a more pleasant correction. Accuracy can be measured but pleasantness can not.

It would be helpful having more samples, and I will do some more testing.

Best regards
Erik

I don't know. I would think IT8 is fine in diffuse, high CRI light. I do know Silverfast says it is not designed for DSLR calibration. I settled on the idea of the IT8 as a gamut test more that a color test for DSLRs.



Imaging Resource has ISO100 raws for a huge number of cameras with a color checker in the shot (still life series). If there is a problem with a raw converter is should be easy to test.

C1 should be designed for MFDB compatibility so it is very surprising if they fail there.
« Last Edit: February 26, 2014, 09:44:23 AM by ErikKaffehr » Logged

ErikKaffehr
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« Reply #22 on: February 27, 2014, 06:21:07 PM »
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Hi,

The SLT 99 is pretty close the Alpha 900 in SMI rating. But I will repeat the test with the A900.

Best regards
Erik


Yes, the A900 was Sony's attempt to make a photographer's camera with no frills, no BS. A large part was the choice to give up some ISO noise for color separation on the filters.
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Sareesh Sudhakaran
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« Reply #23 on: February 28, 2014, 03:00:12 AM »
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Hi Sareesh,

Unfortunately, no. I have two issues with skin, I have exactly two portraits shot with my P45+, one of those is showing myself, and that one is discussed here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/79-p45-colour-rendition?start=6 .

The other issue is that as I am a landscape shooter, I cannot really say what skin looks like.

But, I have found some oddball issues with the Adobe Standard profile on the P45+, that I fixed by generating a DCP profile, see below:


So I would say that a profile may be reasonably accurate and still produce outliers. The P45+ with the C1 linear profile has outliers at DeltaE* = 17.2, while LR 5.3 with my home made profile has a Delta E of 7.13 for the same patch. Still, the very same patch on the SLT 99 has a Delta of 1.48.

I had downloaded a two raw files from Nikon D3X and Aptus (of some kind). In those images the D3X had a pinkish skin tone with the Adobe Standard profile, but the exposure also included a ColorChecker,
which enabled me to create a DCP profile that removed the pinkish tone. The D3X still looked flat compared to the Aptus.

The image below shows the outliers:

P45+ with capture one on the left, P45+ with LR5.3 at the center and SLT 99 on the right. The LR5.3 files use DCP profiles generated from a ColorChecker Passport.

Best regards
Erik

Thanks for sharing! From a quick peek at your photos on your site, I prefer the C1 look, but I might not know what I'm seeing so I'll read through them this week and get back to you.
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« Reply #24 on: March 02, 2014, 02:12:36 AM »
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Hi,

After doing some additional experiments here some summary.

My findings here focus Delta E* using the CIEDE 2000 formula. A possible interpretation DeltaE* may be:

  • DeltaE* = 1, barely detectible
  • DeltaE* = 3, visible in images
  • DeltaE* = 5, objectionable deviation

I found that of my two cameras tested the Sony Alpha 99 had the lowest DeltaE* using Adobe Lightroom 5.3 with a home made DCP profile, but Adobe Standard profile was close, so I will normally use the AdobeStandard profile on that camera.

With the P45+ the issue is a bit more complex. What I found initially was that Lightroom 5.3 with both Adobe Standard profile and my home cooked DCP profile produced smaller deviations than the Studio flash profile in C1 I compared with. But, I also know that I was not satisfied with the Adobe Standard profile, the very reason I generated my "dcp" profile. Very obviously Delta E* doesn't tell whole story.

Switching to linear curve improved the statistics, with linear curve C1 produced small deviations, almost as good as the Sony.

I would presume that DeltaE* takes both Luminance, chroma and hue into account, and the film curve varies luminance intentionally. Using the linear curve I assume L stays linear/straight in some sense.

So this would indicate that linear curve in Capture One gives good rendition and my guess is that film curve just adjusts tonality.

I also made a comparison between "Portrait natural" and "Flash" in C1 and the differences were very small (way below DeltaE* = 2 on individual patches) and mostly in areas nearly skin tones. I presume that we see some of the "image professor's" hand at work. Very small subtle effects in selected areas. Delta E* mean between the two was just 0.51. I enclose the comparison between the linear profile and portrait profile.

The outdoor daylight profile and the flash profile were essentially identical, no deviation at all.

Personally, I feel I have learned a lot about the options I have at hand.

Best regards
Erik
« Last Edit: March 02, 2014, 02:44:09 AM by ErikKaffehr » Logged

bjanes
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« Reply #25 on: March 02, 2014, 11:02:35 AM »
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Using Delta C or Delta L alone would not give any good information. C is essentially saturation, pretty meaningless without hue angle. H is hue angle (essentially). There can be large variations in hue angle for areas of low saturation without a visible difference. So Delta C or Delta H alone give little useful information.

Eric,

I think you are using ΔC too restrictively. My knowledge of color difference formulas is largely limited to those used in Imatest and explained in the supplementary documentation. ΔC* refers to differences in chroma, but other ΔCs include ΔCab, ΔC94, ΔCcmc, and ΔC00. One can omit L* with these formulas and they would be better for your purposes than ΔE. What are your thoughts?

Best regards,

Bill
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ErikKaffehr
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« Reply #26 on: March 02, 2014, 02:28:32 PM »
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Hi Bill,

I used "Patchtool" for this and I don't think it has a "Delta " mode which excludes L but includes color. I tested both C and H. C just says how saturated a color is and H can vary wildly. In some cases I have seen C = 0 and hue angle varying 180 degrees.

My version of Imatest doesn't handle IT 8.7 tagets, AFAIK.

I feel that a proper comparison needs to eliminate L, as it is essentially tone curve. Capture One having linear curve is really a nice feature, at least for testing by the numbers.

Best regards
Erik

Eric,

I think you are using ΔC too restrictively. My knowledge of color difference formulas is largely limited to those used in Imatest and explained in the supplementary documentation. ΔC* refers to differences in chroma, but other ΔCs include ΔCab, ΔC94, ΔCcmc, and ΔC00. One can omit L* with these formulas and they would be better for your purposes than ΔE. What are your thoughts?

Best regards,

Bill
« Last Edit: March 02, 2014, 02:39:13 PM by ErikKaffehr » Logged

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