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 -----Original Message----- From: Iliah Borg <iliah.i.borg@gmail.com> Sent: Friday, June 21, 2019 6:33 PM To: graxx@videotron.ca Cc: Colorsync-users@lists.apple.com Subject: Re: Exposure Value Dear Roger, Based on your gray card NEF: You are in 14-bit mode, maximum is 2^14-1-black level (600) = 15873; average on the card (and the card seems to have some rather strong imperfections) is 1181 (you can check with RawDigger, trial version is enough). That puts the exposure at log2(1181 / 15871) = 3.75 EV below clipping; the camera is calibrated to produce midtone 3.35 EV below clipping, that means the exposure is 0.4 EV below the midtone. Nothing dramatic so far, provided that the card has a lot of wear and tear on it, it isn't shot out of focus, and not at an angle as it should be (see http://www.zonephoto.it/images/pdf/kodak-grey-card1903061.pdf ). The result is mathematically inconclusive - but from my experience I would be expecting something like the numbers above, given how the shot was taken, and would say that metering is calibrated OK. Of course, if you could re-shoot we will be able to come to a more definite conclusion. On Jun 21, 2019, at 6:03 PM, Roger Breton via colorsync-users wrote:
I will get to the Gray Card NEF in a few minutes, Ilah, but I thought I would try turning on Image quality = NEF + JPEG in the camera shooting menu?
And I got very different results? See this link: https://1drv.ms/u/s!AkD78CVR1NBqkLVK68wxOJ6dhvv2nQ
On the left hand side is the JPEG opened in Photoshop as usual, and on the right hand side is the RAW, opened in CameraRAW. The only thing that I could say is the Histograms are very different, this time, extending well into the highlights...
Thanks for you guys patience and help. I'm trying to contact Nikon tech support...
Best / Roger
-----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca@lists.apple.com> On Behalf Of Roger Breton via colorsync-users Sent: Friday, June 21, 2019 5:44 PM To: 'Wayne Bretl' <waynebretl@cox.net>; Colorsync-users@lists.apple.com Subject: RE: Exposure Value
I just tried with ViewNX2 and it is still too "dark"? So it is not coming from CameraRAW -- good news 😊
ViewNX2 link is here: https://1drv.ms/u/s!AkD78CVR1NBqkLVIL-cOCJBYIX0LuA
CameraRAW link is here: https://1drv.ms/u/s!AkD78CVR1NBqkLVJgBzv-yK7ygFD7g
The histograms are not lying, this is under-exposed.
Best / Roger
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-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
Dear Roger, Without further evidence, it is still a mystery why your original raw-file-only mode pictures show apparent underexposure, and the ones taken after choosing raw + jpeg do not. Is it possible you changed another mode setting, like going from Program to Full Automatic, or some other setting (matrix, spot, center average) that changed the exposure metering mode in your camera? Some modes may center the dominant exposure sensing on the in-focus point, for example. Some cameras also have an automatic tone curve adjustment (possibly enabled or disabled according to the exposure mode and/or in a menu somewhere) that attempts to recognize and compensate for various types of images. This is an opportunity for the camera to do things you don't like, as well as possibly rescuing some shots for the unknowledgeable person using full automatic mode. Another thing to note is that while the data in the raw file is supposed to be a mostly untouched rendering of the light falling on the sensor, the rendering output of the raw processor definitely is not so simple. The rendering is not even simply an application of a gamma curve to match the standard jpg 1/2.2 power. That sort of simple process was used in very early digital cameras adapted from video chips, such as the Sony Mavica, and was universally disliked compared to film. Now, raw processors always apply an S curve, mimicking film, because this provides the best looking result: an increase in contrast (at least for the mid tones) to compensate color appearance effects of the human visual system, and a gradual toe and shoulder to accommodate highlights and shadows without severe clipping. This is one example of the kind of behind-the-curtain processes, the details of which are buried in the camera profile and never revealed to the user by Adobe camera raw. Regards, Wayne -----Original Message----- From: colorsync-users <colorsync-users-bounces+waynebretl=cox.net@lists.apple.com> On Behalf Of Roger Breton via colorsync-users Sent: Friday, June 21, 2019 7:15 PM To: 'Iliah Borg' <iliah.i.borg@gmail.com> Cc: Colorsync-users@lists.apple.com Subject: RE: Exposure Value 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 -----Original Message----- From: Iliah Borg <iliah.i.borg@gmail.com> Sent: Friday, June 21, 2019 6:33 PM To: graxx@videotron.ca Cc: Colorsync-users@lists.apple.com Subject: Re: Exposure Value Dear Roger, Based on your gray card NEF: You are in 14-bit mode, maximum is 2^14-1-black level (600) = 15873; average on the card (and the card seems to have some rather strong imperfections) is 1181 (you can check with RawDigger, trial version is enough). That puts the exposure at log2(1181 / 15871) = 3.75 EV below clipping; the camera is calibrated to produce midtone 3.35 EV below clipping, that means the exposure is 0.4 EV below the midtone. Nothing dramatic so far, provided that the card has a lot of wear and tear on it, it isn't shot out of focus, and not at an angle as it should be (see http://www.zonephoto.it/images/pdf/kodak-grey-card1903061.pdf ). The result is mathematically inconclusive - but from my experience I would be expecting something like the numbers above, given how the shot was taken, and would say that metering is calibrated OK. Of course, if you could re-shoot we will be able to come to a more definite conclusion. On Jun 21, 2019, at 6:03 PM, Roger Breton via colorsync-users wrote:
I will get to the Gray Card NEF in a few minutes, Ilah, but I thought I would try turning on Image quality = NEF + JPEG in the camera shooting menu?
And I got very different results? See this link: https://1drv.ms/u/s!AkD78CVR1NBqkLVK68wxOJ6dhvv2nQ
On the left hand side is the JPEG opened in Photoshop as usual, and on the right hand side is the RAW, opened in CameraRAW. The only thing that I could say is the Histograms are very different, this time, extending well into the highlights...
Thanks for you guys patience and help. I'm trying to contact Nikon tech support...
Best / Roger
-----Original Message----- From: colorsync-users <colorsync-users-bounces+graxx=videotron.ca@lists.apple.com> On Behalf Of Roger Breton via colorsync-users Sent: Friday, June 21, 2019 5:44 PM To: 'Wayne Bretl' <waynebretl@cox.net>; Colorsync-users@lists.apple.com Subject: RE: Exposure Value
I just tried with ViewNX2 and it is still too "dark"? So it is not coming from CameraRAW -- good news 😊
ViewNX2 link is here: https://1drv.ms/u/s!AkD78CVR1NBqkLVIL-cOCJBYIX0LuA
CameraRAW link is here: https://1drv.ms/u/s!AkD78CVR1NBqkLVJgBzv-yK7ygFD7g
The histograms are not lying, this is under-exposed.
Best / Roger
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-- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com _______________________________________________ Do not post admin requests to the list. They will be ignored. colorsync-users mailing list (colorsync-users@lists.apple.com) Help/Unsubscribe/Update your Subscription: https://lists.apple.com/mailman/options/colorsync-users/waynebretl%40cox.net This email sent to waynebretl@cox.net
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
Hello Mr. Breton, When you are looking for a new gray card, may I suggest that the SNI value calculated in SpectraShop may be of use. The SNI is the Spectral Neutrality Index, a value which I have developed to evaluate neutral references. This value is an indicator of a specimen's spectral uniformity. The scale is 0-100, with 100 being a spectrum that is monotonic in value. Here are some example SNI values. Perfect reflecting diffuser 100 Fluorilon FWS-99 2009 99.9 Spectralon SCS-99 99.7 Kodak Gray Card 1977 (3 specimen average) 95.0 ColorChecker Passport 2013-12 Neutral 9.5 52.2 ColorChecker Passport 2013-12 Neutral 5.0 95.2 The SNI formula is based solely on the spectral values, no perception is involved. This allows for material evaluation alone. Notice that the white patch (Neutral 9.5) of the CC Passport has a much lower SNI than the Neutral 5 patch from the same chart. This is due to the high absorbance of violet wavelengths by the titanium dioxide colorant used for the white and also the slightly yellow color of the same titanium dioxide. This can be readily observed by placing a Fluorilon or Spectralon 99% reflecting tile (scintered PTFE) next to any white material containing titanium dioxide (TiO2). The TiO2 material will appear slightly yellow since the human vision system will adapt to the tile’s white, allowing the true color of the TiO2 to be observed. The SNI value was created specifically to answer questions about which material is more spectrally neutral. I find it very useful for checking gray reference materials such as gray cards. These articles on my website may also be of use. Neutral References for Digital Camera Calibration http://chromaxion.com/information/neutral_references.html <http://chromaxion.com/information/neutral_references.html> Gray or White Card for Neutral Balancing? http://chromaxion.com/information/gray_or_white.html <http://chromaxion.com/information/gray_or_white.html> Regards, Robin Myers Robin Myers Imaging robin@rmimaging.com robin@chromaxion.com 925-519-4122
On 21 Jun 2019, at 19:14, Roger Breton via colorsync-users <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
-----Original Message——
<snipped for brevity>
On Jun 22, 2019, at 10:31 AM, Robin Myers via colorsync-users <colorsync-users@lists.apple.com> wrote:
Perfect reflecting diffuser 100 Fluorilon FWS-99 2009 99.9 Spectralon SCS-99 99.7 Kodak Gray Card 1977 (3 specimen average) 95.0 ColorChecker Passport 2013-12 Neutral 9.5 52.2 ColorChecker Passport 2013-12 Neutral 5.0 95.2
Spectralon is great stuff, but damned expensive. Expect to pay as much for a Spectralon target as a Canon L series lens. There’re two homebrew-style options that are typically plenty “good enough” in photographic settings. The first, if you want 99%+ reflectance, as close to “pure white” as you’re going to get without spending lots of money: PFTE (Teflon) thread seal tape. Not very durable, and it’s got basically an eggshell surface that’s a bit more specular than ideal (Spectralon is close to ideally Lambertian)...but it’s dirt cheap and you can get it anywhere. Use a bit of creativity and you can figure out how to wrap several layers around a card to make a target. If it gets dirty or damaged or lost...no biggie; all you’ve invested is your time, so just make another. The second is a styrofoam coffee cup (or packing material, etc.) Its total reflectance is a lot less...in the 80% range. But it’s much more spectrally flat than the photographic tools (ColorChecker, gray card, etc.). Outdoors or in mixed lighting, its near-cylindrical shape lets you sample the illuminant from all angles, which can be creatively useful. And, with the right combination of lens and cup, you can fit the cup over the lens and get a near-ideal uniform sampling of all the light in the scene — much like those hundreds-of-dollars custom white balance tools that fit over the lenses do, but, again, with near-perfect spectral uniformity. (Put the cup over the lens, take a picture, and use it for your in-camera custom white balance. It’s probably pretty close to where you want to meter, too; experiment some and you could get that dialed in perfectly and consistently.) Coffee cups are pretty reliable spectrally; the more creative shapes you might find in a craft store (spheres, cubes, etc.) are more hit-or-miss. Visually compare with some thread seal tape (if you don’t have a spectrometer) if you’re unsure. Last note: read everything Iliah has on the Raw Photo Processor / RawDigger Web site and accompanying blog. You couldn’t ask for a better crash course on camera exposure, metering, development, etc., etc., etc. Cheers, b&
On Jun 22, 2019, at 10:31 AM, Robin Myers via colorsync-users <colorsync-users@lists.apple.com> wrote:
Perfect reflecting diffuser 100 Fluorilon FWS-99 2009 99.9 Spectralon SCS-99 99.7 Kodak Gray Card 1977 (3 specimen average) 95.0 ColorChecker Passport 2013-12 Neutral 9.5 52.2 ColorChecker Passport 2013-12 Neutral 5.0 95.2
A couple of layers of heavy weight Tyvec is pretty good and relatively cheap, at 98.5 Graeme Gill.
Dear Mr. Myers: Incidentally, I used your SpectraShop application to measure and plot the reflectance of Teflon thread seal tape: http://www.fastrawviewer.com/sites/fastrawviewer.com/files/Results-fromSpect... http://www.fastrawviewer.com/sites/fastrawviewer.com/files/SealTape_PTFE_gra... (for https://www.fastrawviewer.com/blog/diy-white-balance-reference article) Your application is a joy to use, thank you for creating and maintaining it. -- Best regards, Iliah Borg LibRaw, LLC www.libraw.org www.rawdigger.com www.fastrawviewer.com
participants (7)
-
Ben Goren
-
Bob Seidel
-
Graeme Gill
-
graxx＠videotron.ca
-
Iliah Borg
-
Robin Myers
-
Wayne Bretl