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I have and I get the same result, the ColorChecker photographs great but the artwork shows too little saturation in the yellows. I've tried sunlight, LEDs, and strobes. So far the strobes with UV and polarizing filters work best. (Some of the watercolor has optical brighteners that glow under UV.)Have you tried using natural light and doing a longer exposure? Just as you see it and take a exposure.
I think that’s pretty normal for trying to repro water colors. I think the light colors get diluted by the light penetrating the paper which sort of lights it up from the back. Even if you put it on black (which seems to help sometime), there’s still a lot of light bouncing around in the paper base. Also the colors are so light and delicate they are toward the fringe areas of the gamut of sensor as well as of the paper.I haven't found any combination where the painting doesn't require tweaking to fully bring out the colors, especially the yellows.
(1) should really say “use a light with a high CRI/CQS and non-spiky spectrum”. While most LEDs have a very middling spectral quality there are LEDs with very high quality spectrums. The DT Photons, for example, are individually spectrally measured at the factory with a minimum value of 98 CRI and 98 CQS.I really haven't read all the replies in detail, but things that come to mind are:
1) Use an incandescent light source, such as a regular incandescent bulb or halogen, the LED's that usually are sold (even professionally) have a color rendering of less than 90%, especially missing the reds, the light spectrum simply isn't there to reproduce all colours. But I think the flash you're using should be fine as the flash tube is also an incandescent light source.
2) Try to expose more towards the left, as you'll loose saturation the more you expose to the right. As I can see from your example, the dynamic ranges of your subjects are quite limited, so even though I'm not completely sure about the technicalities of this approach, I still think given the circumstances, it's worth a try at least.
I only do this kind of work occasionally, but those are the suggestions that came to mind to me as well, especially after reading this:1) Use an incandescent light source
2) Try to expose more towards the left
I have and I get the same result, the ColorChecker photographs great but the artwork shows too little saturation in the yellows. I've tried sunlight, LEDs, and strobes. So far the strobes with UV and polarizing filters work best. (Some of the watercolor has optical brighteners that glow under UV.)
Thanks for the breakdown of your process Christopher,The one material that is exceedingly neutral is sintered PTFE (teflon), which can be had in small sheets from Thorlabs.
Thanks for the offer but I have switched to Prophoto strobes now.Craig
If you want I have some Einsteins I have not used for some time and if you want I can just send them to you to see if it helps your situation. I have been planning to do nearly the same for some time and now see the inherent difficulties.