Accuracy of color rendition in converters - lightly quantitative

[Erik Kaffehr]

I can tell an interesting experience. I spilled some curry on my clothes. I washed them and they did not show any stain after washing. So, I went on a business trip and discovered that the stain was still there in daylight. Painful!

At home I checked, no stain. I had some power saving light.

So, I pulled out my Ott-lamp, that has some oddball combination of spectral spikes that approximate daylight and the stain became visible again.

Interesting story, Erik !

It would be cool, to see how that can work at the level of the various spectra. I am particularly curious about the curry stain and the Ott lamp which is unknown to me.

A person, so interested in color science as you, may still have missed the fact that with the i1Studio, you can buy a versatile photo-spectrometer for color management and more for about 500$. I got one. For spectra, I operate it in Argyll line command control using its function spotread. To grossly check its calibration, I measured the solar spectrum on a suitable day and compared it to the official published reference spectrum.


Solar Spectrum 380-730nm, area plots derived from ASTM G-173 reference spectra: box averaged for 10nm resolution. blue: extra terrestrial spectrum, green total AM1.5 spectrum, details see ASTM, red direct+circumsolar light. White line as measured in high resolution mode (3.33 nm steps, 10 nm resolution) using X-Rite i1Studio photo-spectrometer near Zurich on April 20 2019 13:30,. sun altitude 54.1 deg. Slightly hazy conditions. Take from 1st floor window. Readout by Argyll spotread -a -s -H (units mW/m^2/nm)

Hi Bernard,

Thanks a lot for the info!

I was aware of the use of Argyll software with the ColorMunki I have. One use was to check out the light from the Ott-lamp, another to determine voltage for 5000K on my Solux lamps when shooting my color calibration targets.

So, nothing new for me, but thanks anyway.

Best regards

Erik

--
Erik Kaffehr
Website: http://echophoto.dnsalias.net
Magic uses to disappear in controlled experiments…
Gallery: http://echophoto.smugmug.com
Articles: http://echophoto.dnsalias.net/ekr/index.php/photoarticles

 

[Bernard Delley]

I was aware of the use of Argyll software with the ColorMunki I have. One use was to check out the light from the Ott-lamp, another to determine voltage for 5000K on my Solux lamps when shooting my color calibration targets.

Just curious, what light is the Ott lamp ? Is this a small fluorescent desk lamp ? The spiky spectrum of fluorescent lamps can do funny things to colors.

 

[Mark S Abeln]

All light sources are difficult. If it’s not pollution turning the air yellow, it’s trees and grass throwing their green cast on everything.

Interesting observation. I'm not usually color-critical—although I've had clients who were extremely sensitive to color shifts—and in ordinary use, I don't have trouble in direct sunlight.

As for shooting Color Checkers at noon, one of the recommendations is to make a dual profile shooting the card in both daylight and a tungsten which reminded me of the original official measurement for the Kelvin of daylight which was made at noon in long ago Washington DC.

The Daylight preset white balance for Nikons seems to match mid-day, mid-summer direct sunlight in the latitude of Tokyo, which is about 35.5 degrees North, and where Nikon is headquartered. I've heard from folks who find the white balance preset on their cameras far too blue, but then they lived at high latitudes. Also, I've read that Leica's

According the manual:

Loading…

www.xrite.com

The general idea is to use two light conditions, widely separated by correlated color temperature, and the software interpolates between them for intermediate color temperatures. So I wouldn't use a Daylight/Incandescent split for fluorescent or LED lighting, as it would not accurately correct for them: I'd rather calibrate for the specific light sources.

 

[Brian Kimball]

Remember that what counts is the shape of the SPD, as opposed to absolute 'height', so they are really very different light sources.

If one shoots indoors under such LED lights, by all means build a profile around it. On the other hand if one shoots outdoors a lot, my feeling is that having a number of daylight illuminated profiles for shooting in such conditions is likely preferable.

Hi Jack,

After watching Andrew Rodney's video on profile creation I've only ever profiled for different illuminants, not for different conditions under the same illuminant.

Specifically, Andrew makes the case that golden hour light, mid-day sun, and overcast conditions all still have the same fundamental illuminant (the sun), and thus nearly equivalent SPD "shapes", and therefore do not require separate profiles.

Your first paragraph quoted above seems to agree with that, but your second paragraph quote that I've bolded doesn't.

Care to expand? I'm not well-versed on these subjects and unfortunately have to rely on the wisdom of others!

Here's a relevant screenshot from Andrew's video. His discussion of this particular topic starts at 9m28s.


From

 

[MrBrightSide]

I’d rather go to Tokyo.

I'd rather calibrate for the specific light sources.

 

[Mark S Abeln]

I’d rather go to Tokyo.

Way too crowded for me! But I greatly enjoyed visiting some of the smaller cities and rural areas in the southwest part of Honshu.

 

[Jack Hogan]

Though there is merit in having dedicated profiles for the approximate conditions one shoots in. Daylight, once compensated, varies less than one might think (or more depending on one's starting point.

Remember that what counts is the shape of the SPD, as opposed to absolute 'height', so they are really very different light sources.

If one shoots indoors under such LED lights, by all means build a profile around it. On the other hand if one shoots outdoors a lot, my feeling is that having a number of daylight illuminated profiles for shooting in such conditions is likely preferable.

Hi Jack,

After watching Andrew Rodney's video on profile creation I've only ever profiled for different illuminants, not for different conditions under the same illuminant.

Specifically, Andrew makes the case that golden hour light, mid-day sun, and overcast conditions all still have the same fundamental illuminant (the sun), and thus nearly equivalent SPD "shapes", and therefore do not require separate profiles.

Your first paragraph quoted above seems to agree with that, but your second paragraph quote that I've bolded doesn't.

Care to expand? I'm not well-versed on these subjects and unfortunately have to rely on the wisdom of others!

Right bf, this is a really easy question to answer qualitatively but a very tough and time consuming one to answer quantitatively. What is equivalent and what is good enough? Different people will have different answers depending on their needs.

I am afraid that I have not put in the time to be able to give you a quantitative answer but I can tell you that I try to stick to a simple matrix for my landscape work (light, color and our imaging/reproduction systems are supposed to be linear all the way to the optic nerve, no?) - and in critical light I tend to capture the illuminant via pocket gray card and CC24 to determine it.

Andrew is quite knowledgeable. I have not watched the video but my feeling reading your bullets is that he is speaking to a generic audience whose objectives may be different than accuracy. For instance, golden hour shooting can be mighty challenging on colors and most people are quite happy to switch to artistic mode, throwing accuracy into the wind, together with any pocket cards.


Golden hour, Accurate Mode, CCT and white balance off the card. Where is the gold?

That looked nothing like what I saw. This was more like it:


Golden hour, CCT via Creative Mode

So maybe one profile is enough, maybe not

Jack

 

[MrBrightSide]

Though there is merit in having dedicated profiles for the approximate conditions one shoots in. Daylight, once compensated, varies less than one might think (or more depending on one's starting point.

Remember that what counts is the shape of the SPD, as opposed to absolute 'height', so they are really very different light sources.

If one shoots indoors under such LED lights, by all means build a profile around it. On the other hand if one shoots outdoors a lot, my feeling is that having a number of daylight illuminated profiles for shooting in such conditions is likely preferable.

Hi Jack,

After watching Andrew Rodney's video on profile creation I've only ever profiled for different illuminants, not for different conditions under the same illuminant.

Specifically, Andrew makes the case that golden hour light, mid-day sun, and overcast conditions all still have the same fundamental illuminant (the sun), and thus nearly equivalent SPD "shapes", and therefore do not require separate profiles.

Your first paragraph quoted above seems to agree with that, but your second paragraph quote that I've bolded doesn't.

Care to expand? I'm not well-versed on these subjects and unfortunately have to rely on the wisdom of others!

Right bf, this is a really easy question to answer qualitatively but a very tough and time consuming one to answer quantitatively. What is equivalent and what is good enough? Different people will have different answers depending on their needs.

I am afraid that I have not put in the time to be able to give you a quantitative answer but I can tell you that I try to stick to a simple matrix for my landscape work (light, color and our imaging/reproduction systems are supposed to be linear all the way to the optic nerve, no?) - and in critical light I tend to capture the illuminant via pocket gray card and CC24 to determine it.

Andrew is quite knowledgeable. I have not watched the video but my feeling reading your bullets is that he is speaking to a generic audience whose objectives may be different than accuracy. For instance, golden hour shooting can be mighty challenging on colors and most people are quite happy to switch to artistic mode, throwing accuracy into the wind, together with any pocket cards.


Golden hour, Accurate Mode, CCT and white balance off the card. Where is the gold?

That looked nothing like what I saw. This was more like it:


Golden hour, CCT via Creative Mode

So maybe one profile is enough, maybe not

Jack

--
Sit!

 

[Jack Hogan]

Sit!

I am sitting, and stop calling me Shirley ;-)

 

[MrBrightSide]

Excellent points. Golden hour, indigo hour, etc., are special cases because unlike other scenes you’re trying to capture the difference between expected and actual. So your goal is more psychovisual than colorimetric. It’s a case of having to use what would logically be the incorrect white balance to capture the scene as it appeared to the human eye.

In other words our brains expect the sky to have an RGB around 98, 122, 157 (ColorChecker sky patch) but to evoke the feeling of delight or awe in your audience you have to use the “wrong” white balance to capture the oranges, golds, and purples.

The other situation where this pertains is when you’re shooting theater performances or anywhere colored gels are in use. I always have to ask the person at the lighting board the underlying color temp of the lighting instruments.

Jack Hogan, post: 63447470, member: 703663"]

Though there is merit in having dedicated profiles for the approximate conditions one shoots in. Daylight, once compensated, varies less than one might think (or more depending on one's starting point.

Remember that what counts is the shape of the SPD, as opposed to absolute 'height', so they are really very different light sources.

If one shoots indoors under such LED lights, by all means build a profile around it. On the other hand if one shoots outdoors a lot, my feeling is that having a number of daylight illuminated profiles for shooting in such conditions is likely preferable.

Hi Jack,

After watching Andrew Rodney's video on profile creation I've only ever profiled for different illuminants, not for different conditions under the same illuminant.

Specifically, Andrew makes the case that golden hour light, mid-day sun, and overcast conditions all still have the same fundamental illuminant (the sun), and thus nearly equivalent SPD "shapes", and therefore do not require separate profiles.

Your first paragraph quoted above seems to agree with that, but your second paragraph quote that I've bolded doesn't.

Care to expand? I'm not well-versed on these subjects and unfortunately have to rely on the wisdom of others!

Right bf, this is a really easy question to answer qualitatively but a very tough and time consuming one to answer quantitatively. What is equivalent and what is good enough? Different people will have different answers depending on their needs.

I am afraid that I have not put in the time to be able to give you a quantitative answer but I can tell you that I try to stick to a simple matrix for my landscape work (light, color and our imaging/reproduction systems are supposed to be linear all the way to the optic nerve, no?) - and in critical light I tend to capture the illuminant via pocket gray card and CC24 to determine it.

Andrew is quite knowledgeable. I have not watched the video but my feeling reading your bullets is that he is speaking to a generic audience whose objectives may be different than accuracy. For instance, golden hour shooting can be mighty challenging on colors and most people are quite happy to switch to artistic mode, throwing accuracy into the wind, together with any pocket cards.


Golden hour, Accurate Mode, CCT and white balance off the card. Where is the gold?

That looked nothing like what I saw. This was more like it:


Golden hour, CCT via Creative Mode

So maybe one profile is enough, maybe not

Jack

--
Sit!
[/QUOTE]

 

[MrBrightSide]

Sorry, thumbs went rogue.

Sit!

I am sitting, and stop calling me Shirley ;-)

 

[MrBrightSide]

Getting back to the OP's question If you want to compare the values you're getting from your cameras to the values that X-rite uses for the patches, here they are. This is the 2010 version from X-rite, there may be a newer edition but I have not seen it.

And disregard the colors you see in these two charts. They're screen shots from X-rite PDFs. Only the numbers are real.

To me, the least understandable part of it is that they report black as 52/52/52 which is higher even than in 4-color printing.

And here's the disclaimer from the PDF containing the chart:

"The data in this file is reported in CIE L* a* b* data for illuminant D50 and 2 degree observer and is being supplied by X-Rite, Inc. This information can be used for personal and educational but not for commercial purposes without license from X-rite, Inc."

 

[Jack Hogan]

Getting back to the OP's question If you want to compare the values you're getting from your cameras to the values that X-rite uses for the patches, here they are. This is the 2010 version from X-rite, there may be a newer edition but I have not seen it.

Formulations changed slightly in late 2014, I haven't seen an official reference since then. Plus in the real world patch colors change with the batch and with time. Babelcolor.com has a nice page on variability.

To me, the least understandable part of it is that they report black as 52/52/52 which is higher even than in 4-color printing.

Well, patch names are just indicative, and their 'black' is really dark gray. Remember that the purpose of the chart is to provide indicative samples of the color solid under the given illuminant. For the relative estimate to generalize well you do not necessarily need to include the extremes, in fact quite the opposite. Some additional thoughts here .

And here's the disclaimer from the PDF containing the chart:

"The data in this file is reported in CIE L* a* b* data for illuminant D50 and 2 degree observer and is being supplied by X-Rite, Inc. This information can be used for personal and educational but not for commercial purposes without license from X-rite, Inc."

Best way to use a CC24 is to measure the spectral response of the patches of your copy with a spectrophotometer or similar instrument. I use a ColorMunki/i1Studio.

Any suggestions for how to best measure a CC24 Passport with it? The ridges get in the way.

Jack

 

[Brian Kimball]

Though there is merit in having dedicated profiles for the approximate conditions one shoots in. Daylight, once compensated, varies less than one might think (or more depending on one's starting point.

Remember that what counts is the shape of the SPD, as opposed to absolute 'height', so they are really very different light sources.

If one shoots indoors under such LED lights, by all means build a profile around it. On the other hand if one shoots outdoors a lot, my feeling is that having a number of daylight illuminated profiles for shooting in such conditions is likely preferable.

Hi Jack,

After watching Andrew Rodney's video on profile creation I've only ever profiled for different illuminants, not for different conditions under the same illuminant.

Specifically, Andrew makes the case that golden hour light, mid-day sun, and overcast conditions all still have the same fundamental illuminant (the sun), and thus nearly equivalent SPD "shapes", and therefore do not require separate profiles.

Your first paragraph quoted above seems to agree with that, but your second paragraph quote that I've bolded doesn't.

Care to expand? I'm not well-versed on these subjects and unfortunately have to rely on the wisdom of others!

Right bf, this is a really easy question to answer qualitatively but a very tough and time consuming one to answer quantitatively. What is equivalent and what is good enough? Different people will have different answers depending on their needs.

I am afraid that I have not put in the time to be able to give you a quantitative answer but I can tell you that I try to stick to a simple matrix for my landscape work (light, color and our imaging/reproduction systems are supposed to be linear all the way to the optic nerve, no?) - and in critical light I tend to capture the illuminant via pocket gray card and CC24 to determine it.

Andrew is quite knowledgeable. I have not watched the video but my feeling reading your bullets is that he is speaking to a generic audience whose objectives may be different than accuracy. For instance, golden hour shooting can be mighty challenging on colors and most people are quite happy to switch to artistic mode, throwing accuracy into the wind, together with any pocket cards.


Golden hour, Accurate Mode, CCT and white balance off the card. Where is the gold?

That looked nothing like what I saw. This was more like it:


Golden hour, CCT via Creative Mode

So maybe one profile is enough, maybe not

Jack

Thanks Jack, appreciate the response. As I usually season my photos with "WB to taste" I'll stick to the one daylight profile for outdoor shots. 100% perfect color accuracy is not my goal. I just want a neutral base to start with.

 

[MrBrightSide]

Do you have the revised numbers?

I believe in precision, but also in letting equipment do its work unmolested. I would assume that the whole X-rite ecosystem is designed to accommodate the expected variance in the color patches. Or not.

As for how to deal with the ridges: Dremel.

Formulations changed slightly in late 2014, I haven't l an official reference since then. Plus in the real world patch colors change with the batch and with time. Babelcolor.com has a nice page on variability.

To me, the least understandable part of it is that they report black as 52/52/52 which is higher even than in 4-color printing.

Well, patch names are just indicative, and their 'black' is really dark gray. Remember that the purpose of the chart is to provide indicative samples of the color solid under the given illuminant. For the relative estimate to generalize well you do not necessarily need to include the extremes, in fact quite the opposite. Some additional thoughts here .

And here's the disclaimer from the PDF containing the chart:

"The data in this file is reported in CIE L* a* b* data for illuminant D50 and 2 degree observer and is being supplied by X-Rite, Inc. This information can be used for personal and educational but not for commercial purposes without license from X-rite, Inc."

Best way to use a CC24 is to measure the spectral response of the patches of your copy with a spectrophotometer or similar instrument. I use a ColorMunki/i1Studio.

Any suggestions for how to best measure a CC24 Passport with it? The ridges get in the way.

Jack

--
Sit!

 

[Ferguson]

Getting back to the OP's question If you want to compare the values you're getting from your cameras to the values that X-rite uses for the patches, here they are. This is the 2010 version from X-rite, there may be a newer edition but I have not seen it.

And disregard the colors you see in these two charts. They're screen shots from X-rite PDFs. Only the numbers are real.

To me, the least understandable part of it is that they report black as 52/52/52 which is higher even than in 4-color printing.

And here's the disclaimer from the PDF containing the chart:

"The data in this file is reported in CIE L* a* b* data for illuminant D50 and 2 degree observer and is being supplied by X-Rite, Inc. This information can be used for personal and educational but not for commercial purposes without license from X-rite, Inc."

OK, but I'm feeling dense.... HOW do I compare?

For example, I took the a photo of the ColorChecker with an A7Riv under LED lights at a sports arena. I used that for a profile, then applied the profile to the shot, exported from Lightroom to Photoshop. In Photoshop I converted to sRGB.

I went to the Neutral 6.5 which calls for 160/160/160. I played with exposure and a bit of curve to get it near that (160,164,166).

The I looked up blue (13) which is (56,61,150). What I got was (0,41,191) so I'm clearly on a completely wrong track.

I saw the other posting about Patchtool, but am hesitant to buy something I don't understand without knowing if it will help me.

Here's the real goal -- I build Adobe DCP profiles in each arena or stadium under their artificial light, usually LED or Mercury Vapor. This seems to true up the colors by my eye and memory. It also seems to make different camera bodies match each other more closely.

When doing an outdoor arena I might shoot in daylight, I do a daylight + night dual illuminant profile. When doing an interior arena I just do the one color.

This seems to work well, mostly, but a new camera and comparing the results with other tools, e.g. their native application, Capture One (which is somehow affiliated with Sony I think) and Lightroom, they are quite different out of the box -- not just different in contrast and saturation and such which I expect, but in actual colors.

THe simple path is to pick the one I like the best.

Apparently the really complicated path is to ask how to tell which one is most correct.

Linwood

 

[Mark S Abeln]

OK, but I'm feeling dense.... HOW do I compare?

You'll need to come up with an objective 'figure of merit' for evaluating your cameras; and pick whichever camera has the best value. I wrote this earlier:

So you end up with 24 different error values, and they will all be different. There is no *one* method that will tell you that one camera is more accurate than another. For example, do you average the sum of the squares of the errors, taking the one with the smallest sum as the best? Or take the average of the absolute values of the errors, so as not to be so biased by outliers? Or do you only consider the largest error, giving that the worst score? Or do you somehow weight the values, giving more credence to errors in the two skin tone patches, or maybe other important memory colors such as blue skies? But beware, the more complicated methods may tend to bite you in the end: simpler is better.

So the problem is coming up with *one* value that gives you a measure of color quality, but there is no one best method of coming up with this value under all circumstances, as it is not possible to perfectly correct all colors.

A major problem, which is not addressed by the ColorChecker target, is that there may be some colors that appear different to your eye (under a given light source and viewing conditions) but may be identical to the camera, or there may be colors that appear identical to your eye but are rendered differently by the camera: this is typically called "metamerism failure". This will vary between camera models and will be affected by some camera settings.

Metamerism (color) - Wikipedia

en.wikipedia.org

For example, I took the a photo of the ColorChecker with an A7Riv under LED lights at a sports arena. I used that for a profile, then applied the profile to the shot, exported from Lightroom to Photoshop. In Photoshop I converted to sRGB.

I went to the Neutral 6.5 which calls for 160/160/160. I played with exposure and a bit of curve to get it near that (160,164,166).

The I looked up blue (13) which is (56,61,150). What I got was (0,41,191) so I'm clearly on a completely wrong track.

Are you trying to adjust the colors even after you did a calibration? So you don't like the calibrations? First of all, I would make sure that you used good practices when shooting the target: making sure that the target is evenly illuminated, that there is insignificant vignetting, that you aren't over- or under-exposing the image, etc.

Or do you really want to make your own calibration? Using Exposure and Curves to do so is inadequate. Along with White Balance, the really powerful tool for doing so is Photoshop's Channel Mixer, but determining the best set of parameters for this requires careful measurements of the color patches along with an Excel spreadsheet with an optimization module installed to do the calculations. And even then you won't get *all* colors perfect, as mentioned above.

You can also do spot color adjustments, where you force individual color patches to specific values, but the trouble with this is that these nonlinear adjustments also drag along an unspecified range of colors along with them, which may not do what you want.

Using the ColorChecker target for calibration is really rather poor, as there are only a few patches and measuring the target is problematical. A much better method is using a spectrophotometer to measure the entire spectrum of the light source, and using a monochromator to actually measure the spectral response of the camera. You then can develop better profiles for your cameras but then you'll still have problems with inaccuracies, simply because the spectral sensitivity of cameras don't precisely match the sensitivity of the average human eye.

I saw the other posting about Patchtool, but am hesitant to buy something I don't understand without knowing if it will help me.

Yes, all of this is pretty complicated and often expensive. One would think that the camera companies—who have a lot of money and can hire experts—would have already done this for you.

Here's the real goal -- I build Adobe DCP profiles in each arena or stadium under their artificial light, usually LED or Mercury Vapor. This seems to true up the colors by my eye and memory. It also seems to make different camera bodies match each other more closely.

OK, so nothing else needs to be done?

When doing an outdoor arena I might shoot in daylight, I do a daylight + night dual illuminant profile. When doing an interior arena I just do the one color.

This seems to work well, mostly, but a new camera and comparing the results with other tools, e.g. their native application, Capture One (which is somehow affiliated with Sony I think) and Lightroom, they are quite different out of the box -- not just different in contrast and saturation and such which I expect, but in actual colors.

Yes. That is a perpetual problem.

DxO's raw processor has an optional module that attempts to make the colors from one camera match those of a different make. That might be of interest to you.

THe simple path is to pick the one I like the best.

Sure.

Apparently the really complicated path is to ask how to tell which one is most correct.

One problem is inherent to the human visual system. Purely accurate colors look dull and tepid when not viewed under the same conditions as photographed: saturation and contrast drop and hues shift when the lighting levels drop, such as when viewing a print under dim lighting or when viewing an image on a monitor. So cameras almost always produce 'juiced' colors which are not strictly accurate but which *look* accurate to the eye.

To analyze this quantitatively, you need a good color appearance model.

Loading…

www.ics.uci.edu

 

[hjulenissen]

If/when we replace paper with 100» oled/microled displays featuring nearly infinite DR, quite high max brightness (more than perfectly white paper in most rooms?), large color gamuts...

Do we introduce adaptive rendering in the display? Commercial tvs do this allready (focusing on moving pictures), but it seems to be more of a gimmick to me. But if one was a perceptual color geek, how would one exploit «electronic paper»?

1. Adjust brightness and white point to measured room illumination?

2. Adjust color rendering to (face tracked) head size ?

 

[Mark S Abeln]

If/when we replace paper with 100» oled/microled displays featuring nearly infinite DR, quite high max brightness (more than perfectly white paper in most rooms?), large color gamuts...

Do we introduce adaptive rendering in the display? Commercial tvs do this allready (focusing on moving pictures), but it seems to be more of a gimmick to me.

Yeah, I don't know what they actually do.

Do they actually use a good color appearance model? (Somehow I doubt it, but I am no expert).

But if one was a perceptual color geek, how would one exploit «electronic paper»?

1. Adjust brightness and white point to measured room illumination?

I think that would be a good start. It would certainly help someone attempting to match colors to prints.

2. Adjust color rendering to (face tracked) head size ?

Hmmm not sure what you mean here.

This company

Loading…

www.eink.com

has some interesting technologies.

 

[Ferguson]

OK, but I'm feeling dense.... HOW do I compare?

You'll need to come up with an objective 'figure of merit' for evaluating your cameras; and pick whichever camera has the best value. I wrote this earlier:

My question was far more specific, but perhaps in that sense also misguided.

Let's say I do a DCP profile in adobe. I then apply the DCP profile to the color checker.

How do I know it worked properly?

Other than "looks OK by eye". Is there a practical, end-user technique that will tell me that, generally speaking, all the software and raw development steps in the middle more or less ended up with the "right" result?

<snip>

I went to the Neutral 6.5 which calls for 160/160/160. I played with exposure and a bit of curve to get it near that (160,164,166).

The I looked up blue (13) which is (56,61,150). What I got was (0,41,191) so I'm clearly on a completely wrong track.

Are you trying to adjust the colors even after you did a calibration? So you don't like the calibrations? First of all, I would make sure that you used good practices when shooting the target: making sure that the target is evenly illuminated, that there is insignificant vignetting, that you aren't over- or under-exposing the image, etc.

That goes to the jist of it -- I'm fairly happy with the results, applied to real world photos.

I probably should stop there, but I didn't.

I also compared the same real world photos with other raw conversion processes. And individually, separately, I'm fairly happy with those results.

My conclusion -- my eye is flexible, and easy to please. A.k.a undiscerning. Compare it to, say, a piano -- I could not tune one, and can barely play, but can definitely tell you when one is off. It kind of "hurts" to listen to. And like photos, piano tuning is not a simple, decided science -- you do not just follow the half ratios in each octave. There's art to it, and like color art I do not understand. 10 pianos could sound quite differently but all be "in tune" and sound ok. Maybe I prefer one to the other, but they do not have that almost "hurt" quality that a really out of tune one does.

Yet lots of people could listen to a very badly out of tune piano and enjoy it equally, and not hear the difference.

Others can see when colors are wrong, and I think they see it better than I. (Note I have been tested and I have no color blindness at all, just like people who might not know a piano is out of tune could test perfectly in all ranges for hearing).

So my question still goes to -- given I do not trust my eyes to be as discerning as I might like, are there techniques I can use to tell if the workflow I use is producing "right" results, so those with more discerning eyes will not go "yuck".

Here maybe what I should be asking is what word goes where I used "right" that can be measured?

Or is there just no practical answer to that -- art remains art (at least within the means of an average hobby photographer)?

<snip>

Using the ColorChecker target for calibration is really rather poor, as there are only a few patches and measuring the target is problematical. A much better method is using a spectrophotometer to measure the entire spectrum of the light source, and using a monochromator to actually measure the spectral response of the camera. You then can develop better profiles for your cameras but then you'll still have problems with inaccuracies, simply because the spectral sensitivity of cameras don't precisely match the sensitivity of the average human eye.

A tool I have works much better for me than a tool I don't.

Seriously -- the answer to my question may be somewhere between "it's not a meaningful question" and "you do not have the wherewithal to answer it". That's OK too.

<snip>

DxO's raw processor has an optional module that attempts to make the colors from one camera match those of a different make. That might be of interest to you.

I'll look, though that has been a very pleasant side effect of these DCP profiles. My D800 and D4 long ago had very different colors run through the same raw process in Adobe. After a DCP profile applied, largely the same (the AWB was also quite different but that's a different conversation). I've been doing it ever since, and colors, especially under jagged spectra lights, tend to be very similar between cameras.

...

Anyway... thanks for trying to educate the ignorant; I'm trying (in either definition of the usage).