Color Management Question

kitjv

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I have noticed that when I send images to an online print lab, the prints are darker than the on-screen image. I assumed that the luminance (i.e. brightness) of my display was set too high. Therefore, in an effort to achieve a better screen-to-print match, I have calibrated & profiled my NEC display to 3 different luminance settings: 120 cd/m2, 100cd/m2 & 80cd/m2. I kept the white point the same (i.e. D65). Then I soft proofed the image 3 times, based on each of the different luminance settings. When I got the sample prints back from the lab, it was obvious that the lower the luminance setting; the brighter the prints. This is what I expected. However, the colors in the image were noticeably "warmer" at the lower the luminance settings. This surprised me since I assumed that the color temperature of a print was based on the white point setting (which remained unchanged -i.e. D65).

Could someone kindly sort this out for me? Is my reasoning wrong?

Thank you for your help.

Kit
 
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You say you soft proofed the image 3 times, but soft proofing itself does not change an image, so you must have done something else as well.
 
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Whether the display luminance and color temperature of the display visually match the print is highly dependent on both the luminance and color temperature of the light used to view the print, so if your display is set to D65, your print viewing light source has to be visually consistent with that. In other words, if you’re saying images proofed on a display set to D65 look too warm on the prints, the next question would be, what is the visual color temperature of the lights used to say that? And there’s an inconvenient wrinkle to this, in that your eye might perceive the same color temperature value differently on screen and in print! This has been discussed in the prepress industry for many years. Sources:
Why Calibrate Monitor to D65 When Light Booth is D50 - XRite website
Which is the best white point setting to use for print work?

I’ve been watching some videos by Wayne Fox that discuss this phenomenon from more of a studio/home printing point of view. He points out that the best white point for a display is not the same number for everybody, it specifically depends on what gets you the visual match against the light source you have chosen for proofing your prints.


Therefore, the only time it automatically works to set the display to D50 or D65 is if a print of a known color-balanced image looks as expected under the lights you have. The reason D50/D65 works for the prepress industry is that it’s what they agree to for printing contracts, so their viewing booths have those lights. But of course once that printed magazine or ad gets out into the real world it will look different under the lighting by the window or on the kitchen table. If we’re just doing photography, we’re not trying to hit a contract specification, so what matters for us is the luminance and color temperature of the light source we will use to verify our prints. So the color temperature of the display should be based on that.
 

kitjv

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You say you soft proofed the image 3 times, but soft proofing itself does not change an image, so you must have done something else as well.
John: Admittedly, I am relatively new to the topic of color management. So please forgive my ignorance. If I could indulge your patience on a couple of basic questions... (1) Am I correct in assuming that prints that turn out darker than the screen image can be attributed to brightness of the monitor being set too high? (2) If the color temperature of the prints are too "cool", this can corrected by lowering the white point (e.g. from D65 to D50)?

If I were to change either the luminance or the white point of the monitor, I assumed that I could achieve the desired result on the prints by re-adjusting the screen image (for example, in the Basic Panel) while soft proofing to the printer/paper profile. If I am completely wrong in my reasoning, I would appreciate your guidance. Thank you so much.
 

kitjv

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Whether the display luminance and color temperature of the display visually match the print is highly dependent on both the luminance and color temperature of the light used to view the print, so if your display is set to D65, your print viewing light source has to be visually consistent with that. In other words, if you’re saying images proofed on a display set to D65 look too warm on the prints, the next question would be, what is the visual color temperature of the lights used to say that? And there’s an inconvenient wrinkle to this, in that your eye might perceive the same color temperature value differently on screen and in print! This has been discussed in the prepress industry for many years. Sources:
Why Calibrate Monitor to D65 When Light Booth is D50 - XRite website
Which is the best white point setting to use for print work?

I’ve been watching some videos by Wayne Fox that discuss this phenomenon from more of a studio/home printing point of view. He points out that the best white point for a display is not the same number for everybody, it specifically depends on what gets you the visual match against the light source you have chosen for proofing your prints.


Therefore, the only time it automatically works to set the display to D50 or D65 is if a print of a known color-balanced image looks as expected under the lights you have. The reason D50/D65 works for the prepress industry is that it’s what they agree to for printing contracts, so their viewing booths have those lights. But of course once that printed magazine or ad gets out into the real world it will look different under the lighting by the window or on the kitchen table. If we’re just doing photography, we’re not trying to hit a contract specification, so what matters for us is the luminance and color temperature of the light source we will use to verify our prints. So the color temperature of the display should be based on that.
Conrad: Thank you for taking the time to offer your thoughts. Given my rudimentary knowledge of color management, I do understand the importance of ambient lighting when viewing prints. (And I will definitely look at the links that you provided). To clarify my situation, I view my prints using a D50 light source. I understand your point that viewing prints that were soft proofed with the monitor calibrated at D65 will appear warmer under D50 ambient lighting. However, here is my confusion (or ignorance). I calibrated the monitor at D65, 120cd/m2. I then soft proofed the image to get a close visual match to the printer/paper profile used by the lab. The image was then set to the lab for printing. The returned print was darker than the screen image. To correct this, I re-calibrated the monitor lowering the luminance to 80cd/m2 (but kept the white point at D65). I then soft proofed the image again to get a close visual match. When I got this sample print back from the lab & compared it to the previous sample print, the print resulting from the 80 cd/m2 setting was brighter when viewed under the same D50 lighting. I expected this since I assumed that readjusting an image in soft proofing (with the luminance of the monitor set lower), would result in a lighter print. But I am perplexed as to why the color temperature of the print also became warmer when soft proofed with the monitor set at 80 cd/m2.

Forgive me if my reasoning is way off base. Maybe the question I should be asking is: if the brightness of a print is darker than the screen image, how can I correct this? Similarly, if the color temperature of a print is warmer than the screen image, how can I correct this?

Thank you for your patience.

Kit
 
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John: Admittedly, I am relatively new to the topic of color management. So please forgive my ignorance. If I could indulge your patience on a couple of basic questions... (1) Am I correct in assuming that prints that turn out darker than the screen image can be attributed to brightness of the monitor being set too high?
Yes. It's impossible to get an exact match, due to the difference between how a monitor displays an image (with emitted light) and a print (reflected light), but if your monitor is clearly brighter (while soft proofing) than the actual print, then the monitor is set too bright.

(2) If the color temperature of the prints are too "cool", this can corrected by lowering the white point (e.g. from D65 to D50)?
I'm surprised that the prints look too cool when viewed under D50 light. If the actual print is cooler than what you see on the monitor (while soft proofing), then the monitor is set too warm or the light you use to view the image is too cold. If your monitor is set to D65 and the light source is D50, then I would expect the print to be too warm... Changing the monitor from D65 to D50 makes sense, but if the print is really too cool then this would increase the difference.

If I were to change either the luminance or the white point of the monitor, I assumed that I could achieve the desired result on the prints by re-adjusting the screen image (for example, in the Basic Panel) while soft proofing to the printer/paper profile. If I am completely wrong in my reasoning, I would appreciate your guidance. Thank you so much.
That is indeed the idea behind soft proofing. You look at the image as if it was printed, so you can make adjustments (which are saved as a virtual copy because these are printer-specific adjustments) to get a better looking print, without having to make real (printed) proofs.

And that is the problem I still have with your story. You wrote initially "When I got the sample prints back from the lab, it was obvious that the lower the luminance setting; the brighter the prints", but that is not obvious at all. Changing the luminance setting of your monitor does not change the actual image and so it should also not change the print. The only thing that should change is that the print better matches what you see in soft proof...

So how do you soft proof (what color profile did you choose?) and what exactly do you send to the lab?
 

kitjv

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Thank you, John, for your reassurance that my reasoning is basically correct. But obviously I still have work to do.

I soft proof in Lightroom Classic using the lab's (ProDPI) "Noritsu37_Luster_032908" profile. The rendering intent is "Relative". The "Simulate Paper & Ink" checkbox is ticked. After I tweak the virtual copy of the soft proofed image to achieve a close match to the original image, I send it to the lab as a JPEG in Abode RGB color space.
 
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Thank you, John, for your reassurance that my reasoning is basically correct. But obviously I still have work to do.

I soft proof in Lightroom Classic using the lab's (ProDPI) "Noritsu37_Luster_032908" profile. The rendering intent is "Relative". The "Simulate Paper & Ink" checkbox is ticked. After I tweak the virtual copy of the soft proofed image to achieve a close match to the original image, I send it to the lab as a JPEG in Abode RGB color space.
OK, so you do edit the image based on what you see in the soft proof! That is vital information that you didn’t mention before. In that case it makes sense that the print gets brighter when your monitor is set darker, because the darker the monitor, the more you’ll increase the brightness during soft proof editing.
 

kitjv

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OK, so you do edit the image based on what you see in the soft proof! That is vital information that you didn’t mention before. In that case it makes sense that the print gets brighter when your monitor is set darker, because the darker the monitor, the more you’ll increase the brightness during soft proof editing.
Sorry for the confusion. Again you have confirmed what I thought was correct reasoning. Going back to my original question...can you offer an explanation as to why the color temperature of the print became warmer as a result of lowering the screen brightness but keeping the white point the same? Thank you.
 
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Sorry for the confusion. Again you have confirmed what I thought was correct reasoning. Going back to my original question...can you offer an explanation as to why the color temperature of the print became warmer as a result of lowering the screen brightness but keeping the white point the same? Thank you.
That might be the printer. I cannot guarantee that the Noritsu machine that is used to print your images is perfectly neutral over the entire brightness range. The Noritsu prints on photo paper, so it 'prints' with RGB light. The RGB color model is a difficult model, because it does not separate color and luminosity (like for example Lab does). Maybe this shifts the colors a bit when the same image is printed darker or brighter.
 

kitjv

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That is certainly one explanation. From what little I know on the subject, there might be other variables at play as well. However, I am foremost a photographer & not a color management scientist.

One other thought I would like to get an opinion on. From various sources from which I have inquired, there seems to be some discussion whether the white point standard of D65 should be changed for a better screen-to-print match. Color management expert Andrew Rodney advises to leave the white point at D65. I assume that by increasing the white point that it would result in a cooler color temperature. Or would I be unleasing other unexpected problems? Your thoughts?
 
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The consensus is indeed that D65 is the preferred setting. However, the whole idea of color management is that colors will become predictable between devices. If setting the white point higher would result in a better match with your printer, then why not try that?
 
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…(And I will definitely look at the links that you provided).…Maybe the question I should be asking is: if the brightness of a print is darker than the screen image, how can I correct this? Similarly, if the color temperature of a print is warmer than the screen image, how can I correct this?
Sorry it took me a while to reply. If by now you have looked at the links and especially looked at the Wayne Fox video, they might help answer the question. The video in particular talks about getting a closer visual match by re-profiling the display. That assumes that the light being compared under is the kind of light you will usually view the print under, and it also means the display profile is tied to how prints look from that specific printing company, and might not represent other printers or displays well. Which might be OK, because it might be workable to create different display profiles matched to different kinds of output and switch as needed, like a general purpose profile and one matched to that printing service.

I’m actually going to have to look into all of that a little more myself, to understand it better.
 

kitjv

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Thank you, Conrad. I am have the lab run some test prints at different white points to see if can get a better match between screen & print.
 
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Color management is quite easy.
Calibrate ( t.ex. X-Rite) your monitor to D65/120 Cd. ( For new printing paper with optical brightener and screen images)
( D50 is for printing on classic news paper/ normal offset paper)
In Photoshop - Colors setting - Adobe RGB
When delivering to a lab ask if the have a calibrated workflow. (The same as you)
If not, they are not useable and find another pro lab.
 
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