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Author Topic: A small comparison of colour accuracy, P45+ vs. Sony SLT99, C1 vs. LR5.3  (Read 2734 times)
ErikKaffehr
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« on: February 22, 2014, 07:14:16 AM »
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Hi,

I just posted a comparison of colour accuracy  between my Phase One P45+ and my Sony Alpha SLT99 using both Lightroom 5.3 and Capture One.

The findings were essentially:

  • The SLT99 has the most accurate colours using LR5.3
  • On the P45+ LR 5.3 is more accurate than Capture One when using Capture One's "film curve" which is default.
  • Capture One is more accurate on the P45+ when using the linear curve than LR 5.3
  • Capture One is significantly less accurate than LR 5.3 on the SLT 99 with both tested curves.

The only case Capture One was better than LR5.3 was when "linear curve" was used with P45+. In all other combinations LR5.3 was more accurate.

Note, this was a measurement of accuracy and not goodness or pleasantness. All alternatives were decently accurate. The results indicate that neither raw converter is markedly superior in colour rendition, but I would say that LR5.3 with a decent DCP profile for the cameras tested seems a bit more accurate.

The results are here: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/79-p45-colour-rendition?start=3

In the figure below P45+ is on the left (using C1 linear curve) and SLT 99 on the right (using LR5.3). Patches Delta E is above 5 are marked.


In the figure below P45+ is on the left (using C1 linear curve) and SLT 99 on the right (using LR5.3). Patches Delta E is above 3 are marked, representing a stricter criteria.


DeltaE* values from an IT 8.7 target are shown below, based on 288 fields.


Best regards
Erik

« Last Edit: February 22, 2014, 09:59:13 AM by ErikKaffehr » Logged

Fine_Art
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« Reply #1 on: February 22, 2014, 03:12:22 PM »
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Nice target, where did you get it, if I may ask?
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ErikKaffehr
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« Reply #2 on: February 22, 2014, 03:26:55 PM »
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Hi,

I didn't show the actual target, it is just a normal IT 8.7, I bought it Woolf Faust, http://www.targets.coloraid.de. Very nice guy!

Best regards
Erik

Nice target, where did you get it, if I may ask?
« Last Edit: February 22, 2014, 03:28:46 PM by ErikKaffehr » Logged

Fine_Art
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« Reply #3 on: February 22, 2014, 03:55:07 PM »
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I like the IT8 target. The only concern with it is it was not designed for color checking DSLRs, it may be highly affected by the source light. Did you use a very high CRI lamp? The normal color checkers use special pigments not affected by the light.

Maybe the IT8 is good for answering the question of camera gamut mapping more than color accuracy?
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ErikKaffehr
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« Reply #4 on: February 22, 2014, 06:05:49 PM »
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No,

Electronic flash. But I don't think it was a problem, as all alternatives were pretty accurate. The reason I didn't use the colour checker this time was that I wanted a target that was different from the CC, specially as I was using the ColorChecker for calibration.

The ColourChecker did show larger Delta E, than my latest test. See below.

Best regards
Erik





I like the IT8 target. The only concern with it is it was not designed for color checking DSLRs, it may be highly affected by the source light. Did you use a very high CRI lamp? The normal color checkers use special pigments not affected by the light.

Maybe the IT8 is good for answering the question of camera gamut mapping more than color accuracy?
« Last Edit: February 22, 2014, 06:08:30 PM by ErikKaffehr » Logged

Sareesh Sudhakaran
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« Reply #5 on: February 22, 2014, 11:08:04 PM »
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Hi Erik, I know you shoot landscape, but was wondering if you have noticed any difference in how skin tones are reproduced?
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ErikKaffehr
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« Reply #6 on: February 22, 2014, 11:55:28 PM »
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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



Hi Erik, I know you shoot landscape, but was wondering if you have noticed any difference in how skin tones are reproduced?
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ErikKaffehr
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« Reply #7 on: February 22, 2014, 11:59:01 PM »
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Hi,

Here are two screen dumps of the Nikon D3X and Aptus images I have downloaded from the net. I don't know whom to attribute them, unfortunately.

The second one shows the image with Adobe Standards Profile to the left and my DCP profile to the right.

My understanding is that Adobe DNG Profile Editor just adjust an underlying base profile, so it is no a profile just based on the colour checker.

Best regards
Erik
« Last Edit: February 23, 2014, 12:28:06 AM by ErikKaffehr » Logged

bjanes
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« Reply #8 on: February 23, 2014, 08:16:16 AM »
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Eric,

Nice work as usual from you. Where does one get the color patch compare tool?

I see that you are using Delta E (CIEDE2000), but why did you choose this parameter which includes differences in luminance, hue and chroma. Exposure error can cause large delta E due to the luminance, but the luminance error component may not be perceptible. The delta C calculation eliminates the luminance component, and may be preferable for most purposes. In my experience with Imatest using the colorchecker chart, I always got the least delta E error using PV2010 with linear settings, but the results appeared flat. Many converters boost chroma leading to increased delta E due to the chroma error component,  but most observers find the increased chroma pleasing. It might be advantageous to correct for chroma error as done in Imatest. However shifts in hue are not welcome.

Regards,

Bill
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BartvanderWolf
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« Reply #9 on: February 23, 2014, 08:21:52 AM »
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Where does one get the color patch compare tool?

Hi Bill,

PatchTool a commercial product, available from here.

Cheers,
Bart
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ErikKaffehr
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« Reply #10 on: February 23, 2014, 10:14:06 AM »
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Hi Bill,

I checked on Delta C, but Delta C ignores both Luminance and Hue. It would be nice get rid of luminance, as it is very tone curve dependent, but I think hue must be kept in any meaningful comparison.
Best regards
Erik

Ps, good input is always appreciated! Thanks a lot!


Eric,

Nice work as usual from you. Where does one get the color patch compare tool?

I see that you are using Delta E (CIEDE2000), but why did you choose this parameter which includes differences in luminance, hue and chroma. Exposure error can cause large delta E due to the luminance, but the luminance error component may not be perceptible. The delta C calculation eliminates the luminance component, and may be preferable for most purposes. In my experience with Imatest using the colorchecker chart, I always got the least delta E error using PV2010 with linear settings, but the results appeared flat. Many converters boost chroma leading to increased delta E due to the chroma error component,  but most observers find the increased chroma pleasing. It might be advantageous to correct for chroma error as done in Imatest. However shifts in hue are not welcome.

Regards,

Bill
« Last Edit: February 23, 2014, 08:54:38 PM by ErikKaffehr » Logged

Fine_Art
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« Reply #11 on: February 23, 2014, 01:55:15 PM »
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Hi,

Here are two screen dumps of the Nikon D3X and Aptus images I have downloaded from the net. I don't know whom to attribute them, unfortunately.

The second one shows the image with Adobe Standards Profile to the left and my DCP profile to the right.

My understanding is that Adobe DNG Profile Editor just adjust an underlying base profile, so it is no a profile just based on the colour checker.

Best regards
Erik

Erik,

On the top comparison, the background on the Leaf looks warmer so the immediate impression is it is off relative to the nikon. Looking at the color checkers the nikon looks much more saturated especially the second column (Caucasian skin tone, blue). Pulling the RGB colors on the bottom grey row the white balance is red on the nikon, it is neutral on the leaf. I think fixing the nikon whibal based on the color checker would turn the person's skin a magenta hue. That profile is way off.
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Fine_Art
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« Reply #12 on: February 23, 2014, 02:01:12 PM »
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On the second one they both seem to drift to the blue at darker tones. The skin tone looks more pleasant with your correction.
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ErikKaffehr
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« Reply #13 on: February 24, 2014, 12:53:37 AM »
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Hi,

What I found was essentially:

- The Sony Alpha 99 had more accurate colours than the P45+, but the P45+ came pretty close using the linear curve with Capture One
- With the Sony Alpha 99 LR5.3 is more accurate than Capture One
- Generating a camera specific DCP profile helps LR 5.3 in both cases
- The linear curve is pretty linear on Capture One and that probably helps a bit on Delta E based evaluation
- The LR5.3 conversion with camera specific DCP profile is more accurate
- C1 conversions seem to shift deep blues and green towards extreme saturations
- C1 has some pretty extreme colour shifts in blues and greens

Some observations on the methods used.

The 288 colour pathches cover a significant part of Adobe RGB, with some patches slightly outside Adobe RGB.

The fact that Sony SLT and LR5 yields very good colour reproduction indicates that the experiment setup is decently useful. It is highly improbable that methodical error would not show up on Sony but on P45+. Also, the linear curve on the P45+ produces average Delta E close the Sony.

As a side note, the Sony is regarded to have good colour rendition by several authors, like Tim Parkin and also Iliah Borg. It also has a very high SMI-rating at DxO-mark.

I looked at using other Delta values than Delta E. Delta E uses L (Luminousity), C (Chromacity) and H (Hue) coordinates. Ideally I would like to ignore L (as this is essentially a grayscale component).

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.

Best regards
Erik
« Last Edit: February 25, 2014, 12:02:46 AM by ErikKaffehr » Logged

Fine_Art
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« Reply #14 on: February 25, 2014, 02:56:08 PM »
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Maybe, maybe not. 1 sample of 2 cameras is not scientific. It is not statistically significant. It is very interesting. I'm sure everyone appreciates the effort.

If your experiment is combined with the raws of many cameras provided by Imaging Resource (they all have a color checker in the shot) on the web, then other testers find the same conclusions, you would have enough to make a definitive statement of ACR vs C1. Probably even enough to get them to improve.

I don't dispute your method or findings, I am just saying it needs verification as well as a broader selection of products.

Maybe several forum members can start looking into the available raws. The work could benefit everyone in photography.
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ErikKaffehr
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« Reply #15 on: February 25, 2014, 03:13:52 PM »
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Hi,

MFD raw images are not a plenty. I have analysed several, and I have always found LR to have an advantage in accuracy. The problem is really that once you calibrate, you calibrate against the 24 colours of the ColorChecker. The real benefit of this test is that it goes "beyond" the colour checker and analyses 288 other patches.

I have no issue with the colour checker, it is just that it covers a limited of colours - albeit probably well choosen - and that it would often be used as base for calibration.

What my test does prove, sort of, is that MFDB is not in general more accurate than a DSLR. I may of course have a bad sample of the P45+ and a good sample of the SLT99. To sort out that question would need a decent sample of each.

Another point may be that the accuracy I have measured using the linear curve on the P45+ was by any means pretty decent. Using a more film like curve may give "better" tonality although it may be less "accurate".

Best regards
Erik


Maybe, maybe not. 1 sample of 2 cameras is not scientific. It is not statistically significant. It is very interesting. I'm sure everyone appreciates the effort.

If your experiment is combined with the raws of many cameras provided by Imaging Resource (they all have a color checker in the shot) on the web, then other testers find the same conclusions, you would have enough to make a definitive statement of ACR vs C1. Probably even enough to get them to improve.

I don't dispute your method or findings, I am just saying it needs verification as well as a broader selection of products.

Maybe several forum members can start looking into the available raws. The work could benefit everyone in photography.
« Last Edit: February 25, 2014, 03:24:53 PM by ErikKaffehr » Logged

Vladimirovich
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« Reply #16 on: February 25, 2014, 03:44:18 PM »
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As a side note, the Sony is regarded to have good colour rendition by several authors, like Tim Parkin and also Iliah Borg.
wasn't that about A900/A850 ?
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Fine_Art
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« Reply #17 on: February 25, 2014, 04:41:23 PM »
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wasn't that about A900/A850 ?

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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Fine_Art
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« Reply #18 on: February 25, 2014, 04:49:55 PM »
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Hi,

MFD raw images are not a plenty. I have analysed several, and I have always found LR to have an advantage in accuracy. The problem is really that once you calibrate, you calibrate against the 24 colours of the ColorChecker. The real benefit of this test is that it goes "beyond" the colour checker and analyses 288 other patches.

I have no issue with the colour checker, it is just that it covers a limited of colours - albeit probably well choosen - and that it would often be used as base for calibration.

What my test does prove, sort of, is that MFDB is not in general more accurate than a DSLR. I may of course have a bad sample of the P45+ and a good sample of the SLT99. To sort out that question would need a decent sample of each.

Another point may be that the accuracy I have measured using the linear curve on the P45+ was by any means pretty decent. Using a more film like curve may give "better" tonality although it may be less "accurate".

Best regards
Erik


I am with you on that, I always felt the standard color checker was lacking compared to the IT8. The special pigments may be hard to mix into the variety of the IT8, or at least the color brightness.

I believe your results on ACR being good. I have a small doubt on the C1 considering so many people like it. Maybe it is marketing and you have pulled the curtain back on the wizard of oz. It would be nice to know what products give a precise "neutral" color.
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Vladimirovich
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« Reply #19 on: February 25, 2014, 04:54:20 PM »
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I am with you on that, I always felt the standard color checker was lacking compared to the IT8.
isn't IT8 way too glossy target to use (and wasn't that the reason why Colorchecker DC failed) ?
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