Roger, I’d like to comment on using RAW and JPG in your experiment. This may just be a reminder since you certainly are aware. I've used the D810 and now the D850 for some time. One thing to consider when comparing the two images: the JPG, displayed on the back monitor and saved as a JPG is “PROCESSED” using any and all settings you've made in the camera. Most importantly color space, color temperature and any definitely any “scene” settings like vibrant, etc. are applied to the saved JPG. The RAW, on the other hand, is truly RAW. You must assign a color space and “develop” the raw data to view the image as measured by the raw sensor data. Unless you compare the settings and apply them the same, the images will be different. I’m also interested in your exposure inquiries. Very important to me when making reproductions of large pieces of art. In the end, after all the calibrations, I must rely on printed test strips laid over the original to assure a match for color and tonality. I’d like to learn more accurate and efficient ways. Bob -- Bob Seidel imediaMagic llc proARTPRINTS.COM <http://proartprints.com/> Bob@proARTPRINTS.COM <mailto:Bob@proARTPRINTS.COM> Bob@imediaMagic.com <mailto:Bob@imediaMagic.com> 5590 Gleneagles Dr. Idaho Falls, ID 83401 (208) 524-0926
On Jun 21, 2019, at 8:14 PM, Roger Breton via colorsync-users <colorsync-users@lists.apple.com <mailto:colorsync-users@lists.apple.com>> wrote:
Dear Ilah,
Thank you so much for applying your vast technical expertise to my humble problem. I realize, again, that there is so much to learn in digital photography, I feel ashamed to have neglected digging into this fascinating part of image processing for so long (It took me more than a few CPU cycles of my brain to figure Exposure Value, today)...
For sure, I need to invest in a "new" gray card, I confess that this one has seen its share of "tales from the trenches".
Having said that, I'm relieved to read in your analysis that my camera "light meter" isn't playing tricks on me or need to go back to the manufacturer under warranty.
I *will* reshoot, for sure, as you suggested. It's an exercise worth every effort and probably investigate using one of your suggested software..
For now, I am not sure what to conclude from my experience? Tomorrow, I will probably experiment with shooting A) RAW alone and shooting B) RAW + JPEG. In "theory", there should not be any difference between the two modes of shooting but if there should be one, then this is going to prove interesting.
Have you had a chance to take a look at my Excel sheet at all? To see whether I correctly applied the metering equations from measured Luminance and Illuminance?
I think the calculations are sound.
One last thing I have not tried and I *will* try is, to shoot with my antique D100, in RAW, to compare with shooting the same scene with the D810, in RAW, to test any potential differences between the two systems, in terms of exposure.
One thing I wonder, as I was thinking about the experimental setup, something completely absurd (?), was, what that, could there be any difference in the underlying capture of the pixels between the two cameras?
Suppose, on the D810, at 1/200s, F/5.6, ISO400, the histogram looks skewed to the left, suggesting some degree of under-exposure (see my earlier links)? Suppose further, on the D100, at the same 1/200s, F/5.6, ISO400 settings, the histogram looks "normal", with pixels distributed throughout the tonal range, from 0 to 255, then what?
Until I'm convinced that there is nothing wrong with this camera, I figure I need to further test it, until I'm fully satisfied that there is nothing "wrong" with it.
Best regards / Roger