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Archive 2011 · Why Color Profile?
  
 
Hrow
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p.1 #1 · Why Color Profile?


I have a thread running here on a calibration issue that specifically mentioned ColorMunki. I am starting a follow-up thread in the hopes of making this a more generic question. The original thread reads in part....

Just got a ColorMunki Photo. I have a two monitor Mac Pro with one 20" Cinema Display and a 24" Cinema HD. I have calibrated both using the same settings, however, the 24" is about 3/4 stop darker than the 20". Have repeated the calibration process a number of times. Same result.

I just heard back from X-Rite support and their response in part was...

When you calibrate multiple monitors to match each other, they may match closely but not exactly which can be extremely challenging for any photographer using dual displays in their workflow for color critical work. You may especially notice a change in cases where you are using a mix of backlighting technologies however even the same model and make of display can render results that may not be a spot on match as the manufacturing can have variables also that might affect these results.

Now the question(s) becomes...

1.Why calibrate a monitor if each monitor is going to look different (3/4 of a stop is a big difference in my mind)?

2. Isn't it the point that they are adjusted to be the same? If they are different, then how do you come up with consistent print output - other than trial and error?

3. If it is trail and error, why do you need to spend money on a calibration device?





Dec 17, 2011 at 02:29 PM
BobCollette
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p.1 #2 · Why Color Profile?


I believe that Apple monitors don't have a contrast control, only a brightness control. Is the brightness control all the way at one end (probably minimum brightness) on one or both monitors? If so, that might explain why the two monitors don't match.

Also, it's not uncommon for the luminance to vary at different locations on the monitor. It could be that the luminance variation is different between the two monitors, and while they have the same luminance in the center (I assume you're calibrating them in the center of the display), the luminance is different over the rest of the monitor.

I've never used the ColorMunki (I have the i1Pro). If the ColorMunki software works in a similar fashion to that of the i1Pro (i1 Match SW), the first few steps calibrate the monitor to the desired luminance, gamma, and white point. The last step is to characterize the display to build the ICC profile. If the ColorMunki software works similarly, you should be able to "cheat" and set the 24" to a slightly higher luminance than the SW tells you is correct, so that the two displays have the same apparent luminance (or set a slightly higher luminance target). Then go ahead and build the ICC profile for the monitor. This should give you a better match between the two monitors.



Dec 17, 2011 at 02:49 PM
Hrow
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p.1 #3 · Why Color Profile?


Maybe I am misunderstanding things... do ICC profiles include brightness? Isn't brightness a component of a color's definition?

I can visually match the two monitors by adjusting the brightness manually but I have been assuming that brightness is an important component to matching what you see on screen with the print output. Maybe I am asking it do something that it is not intended to do.



Dec 17, 2011 at 04:28 PM
BobCollette
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p.1 #4 · Why Color Profile?


The ICC profiles don't affect brightness. If you adjust the brightness so that the two monitors match and then characterize them (build the profiles) using the ColorMunki, you should be good. If you profile the monitor and then change the brightness, then the profile would no longer be accurate, but if you change it before you profile, the profile will be accurate.


Dec 17, 2011 at 04:45 PM
skibum5
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p.1 #5 · Why Color Profile?


Hrow wrote:
I have a thread running here on a calibration issue that specifically mentioned ColorMunki. I am starting a follow-up thread in the hopes of making this a more generic question. The original thread reads in part....

Just got a ColorMunki Photo. I have a two monitor Mac Pro with one 20" Cinema Display and a 24" Cinema HD. I have calibrated both using the same settings, however, the 24" is about 3/4 stop darker than the 20". Have repeated the calibration process a number of times. Same result.

I just heard back from X-Rite support and their response in part
...Show more

Usually the brightness reported wouldn't vary so much but maybe one of them has such extreme and thin peaks in the primaries it's not reading the brightness correctly??

Also if a lot of corrections need to be applied the calibration program may end up needing to lose some top end brightness, so when using a monitor that needs certain types of tone curve corrections you may need to preset the monitor to a higher level and then it calibrate it down to what you had wanted otherwise it won't have room and it might make it darker.

And some software tells you to try to adjust brightness and some doesn't bother to mention that and some tries to fine tune it, if possible, itself a little, it depends what program you are using too.


Aside:
It is true that even if the probe reads the same values on different monitors they may look different to the eye, especially when you compare wide gamut CCFL to CCFL or even to LED since the primary colors have different spectral spikes which might be partly missed by a spectro not costing $$$$$$$$$$$$$$$$$$$$$$$$$$$$ since they may be too thin for it's precision and even regardless of lot the general metamerism issue and the way the spikes in the primary colors spectrum are can alter a human's sense of what color is being shown by a simple R,G,B combination.

The simple 3 stim R,G,B color model is actually too simplistic and can never work to allow someone to see the same photo across different screen types exactly the same way. Even moreso it can't even be corrected for although some monitor try to offer special matching transformations since each individual's eyes have a slightly differerent response to the various spectral peaks in the primaries and one person might see a certain pic look the same one some wide gamut and some sRGB monitor and another might seem some differences and another might seem some differences only in a different way.

The onyl way to get around that would be to go an entirely new form of color management which would be spectrum based and require detailed spectral measurements and then you'd tune the energy at each part of the spectrum and apply correction as needed and then you could get everything to look the same to everyone across all the technology types. I'm not aware of any software/hardware outside of a research lab that takes this approach.

If I make a grayscale chart measure the same on a wide gamut and sRGB monitor and then compare to chart in real life viewed under as close to D65 as I can get, sadly all three don't really quite look the same to me viewed side by side. I see a clear difference between sRGB and wide gamut monitor even though probe says they are the exact same since the eye has a complex response. It is a bit worrisome since then what happens if I ever had to move back to sRGB monitors only or what if the spikes on the primaries of the next OLED tech look different? Then all my careful colro tunings will look different? Anyway to my eyes at least what I see on my wide gamut display actually looks closer to what i see with the real world chart than what I see on my sRGB monitors so to me the way my eye reacts to the wide gamut monitors seems more true to life to me.

So a simple tristimuls model won't work 100% since each of the three stimula will have a different set of spectral spikes depending upon what phosphors/filters/backlighting/diodes etc. are used and your eye interprets each of three primaries differently depending upon the spectral profile of each primary. So you can't have a perfect model where you just measure how much red and green and blue you need to measure how much energy is put out across the ENTIRE visible light spectrum when you take measurements instead of just recording a triplet.

Edited on Dec 17, 2011 at 09:24 PM · View previous versions



Dec 17, 2011 at 06:38 PM
skibum5
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p.1 #6 · Why Color Profile?


For my NEC I make a set of calibrations at 120 cd.m^2, 110, 100, 90, 85, 80 and use whichever one fits the current room lighting conditions.



Dec 17, 2011 at 06:41 PM
Hrow
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p.1 #7 · Why Color Profile?


Sorry if I'm being dense here so I'll ask the base question a different way....

If the screen brightness is variable in the calibration process, how does one consistently match the brightness of the image on screen to the print output brightness?




Dec 17, 2011 at 07:10 PM
BobCollette
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p.1 #8 · Why Color Profile?


The reason the monitor luminance (screen brightness) is a variable is because the optimum value depends upon your print viewing conditions. In general, the brighter the print viewing environment, the higher the monitor luminance should be. Many people find that a monitor luminance somewhere in the range of 90-120 cd/m^2 is appropriate, but there is no absolute value that it should be calibrated to. As Skibum5 points out, unless you have a dedicated print viewing box (or some other form of fixed lighting), the optimum monitor luminance can change over the course of a day if there is ambient light from outside entering the room. You would need a higher luminance on a bright, sunny day than you would on an overcast, cloudy day.


Dec 17, 2011 at 07:36 PM
JimboCin
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p.1 #9 · Why Color Profile?


A very interesting discussion! I really appreciated skibum5's and BobCollette's comments.

I believe part of the problem is that the calibrators and software we use are relatively inexpensive and inaccurate devices, not high-end, high-precision calibration devices.

I use a NEC IPS monitor of moderate cost. I calibrated my monitor with a Spyder3 Elite. It looked better than what I had done by eye using the manual methods. I then borrowed a friend's calibrator - and the results were visibly different than my Spyder3. If I calibrated my monitor with one calibrator, I was expecting it to look the same with another calibrator. That expectation was wrong.

I then got a X-Rite eye one Display 2 and an X-Rite DTP94B calibrator. Each one of them produced visibly different results - with the settings as similar as I could get them to be.

I was not sure to what degree the difference was due to the calibration hardware versus the calibration software, so I bought basICColor Display 4 software that would allow me to use the various hardware calibration devices with the same software and exact same settings.

Guess what? The results were closer, but still visibly different between the various hardware calibration devices.

My take through all of this is that doing a hardware calibration (using these relatively inexpensive devices) helps to get things better, but the eye can still detect differences.

My goal was to get my monitor to match my test print under my lighting conditions. The test print I used was one of those that is available for free on the internet. I use WHCC for my printing.

I downloaded the printer profiles for the various WHCC printers and paper and use them for soft proofing in Photoshop. I purchased a good viewing light that I am very happy with. I carefully control the lighting level in my viewing room, which is painted a neutral color.

After initial calibration / profiling of my monitor using the hardware calibrator that seemed to give the best results for me, I tweaked my basICColor software setup and the RGB settings so that it resulted in as close a match as I could get to the test print. I found a person who had done the exact same thing - and he offered invaluable assistance to me. Some of the settings I used (luminance and white point) that I ended up with were not what others have commonly said - but my goal was to obtain a good match, not to follow numbers that others had recommended.

After all of this I have a monitor to print match that to my eye is so close to perfect that I am very happy with the result.

There are people who have told I am doing everything wrong. I guess that does not matter to me, as I am getting what I set out to get - a good match between my monitor and my prints under my viewing conditions.



Dec 17, 2011 at 08:25 PM
theSuede
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p.1 #10 · Why Color Profile?


Hrow wrote:
Sorry if I'm being dense here so I'll ask the base question a different way....

If the screen brightness is variable in the calibration process, how does one consistently match the brightness of the image on screen to the print output brightness?



Exactly HOW are you going to define "... the print output brightness" if I may ask

The main question you should ask yourself (a question reflected on your own question) is : HOW are you going to make sure that the print is always illuminated to the EXACT same intensity for every possible situation? What "luminance" does a print have?

---A print doesn't have a "brightness", or luminance (unless you print with glow-in-the-dark selfluminescent/phophorescent inks!). A print reflects the light you shine on to it. The "paper white" reflects maybe 90%, the deepest black you can get reflects around 1%. This means that the "luminance" is always ~90% of the relative illuminance you apply on to the print. If you shine twice as much light on it, apparent "luminance" grows by a factor two, or one Ev. Put the print in a protective envelope and place the envelope in a drawer - and the print brightness is zero since no light hits the print surface.

The fix meaning of the word luminance, as used for an emitting source of light, can however be used about a screen. And, to make the screen seem as bright as a paper white under what we could call "normalized lighting conditions" you need to make the screen conform to some kind of standard. This is normally around 70-150, a full Ev of difference can be applied depending on the site the screen is viewed at.

The screen is relative to your surrounds in the opposite way to a print. If you place two identically bright screens - as measured in cd/m - in two rooms with different ambient lighting strength, the screen in the room with more light will look darker, and have a (perceptually) lower contrast at a first glance. Two identical prints will have the opposite behavior - the one viewed in the darker room will (perceptually) be darker and have a lower contrast.

Your eyes do however adapt to a screen in a very different way (the screen tends to be a adaptive reference on its' own after you've looked at it for a while), and this means that we can specify a fairly tight interval of "normalized brightness" that should make you PERCEIVE the contrast of the screen just as you would perceive the contrast on a print viewed in a certain minimum illuminance. Making the screen brighter and keeping the actual contrast the same will make you perceive the screen as "having more contrast". This in turn makes you perceive colors as "more saturated" even though their chromaticity will measurably be identical to before.
That's why the definition of baseline screen brightness exists.



Dec 18, 2011 at 11:06 AM
 

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Hrow
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p.1 #11 · Why Color Profile?


theSuede.

I realize that a print "brightness" will vary dependent on the viewing conditions.

Here's the problem... in the past, I have set-up my monitors using Apple's built-in calibration and compared them to printer output using the ICC profiles provided by the paper manufacturer. The prints closely approximate what I see on screen but some adjustments are necessary to get them closer. I have those adjustments set-up as an action that I run prior to printing.

Everyone I know keeps telling me that I need to calibrate my monitors - so I do. Now they are "officially" calibrated and both screens are different from one another. I also calibrated using a friend's Spyder, and they are different from either the manual calibration or the ColorMunki - now the dark screen is lighter and the light screen darker. That's problem one. Two calibrators x two monitors = four different results.

Problem two is that now if I create an image that I am happy with on screen and print it using my old action (or just straight) it is way too "bright" (by my reference) as the calibrator would have me lower the brightness level of my screens significantly. In other words, my screens are darker so to make the image look the way I want it while working on it, I need to "brighten" them up - a lot.

Thus, the question of thread arises from two things. It appears that a reasonably expensive calibrator can not set-up two monitors running from the same graphics card so that they look remotely similar. Why then calibrate? If what I see on screen has to be adapted in "brightness" to individual printers when I have profiled my monitor to ICC standards and used ICC profiles for the printer then what good are the ICC standards because they really don't accomplish much.

I am really trying to understand why calibration is so "necessary". If it is just to get you a little closer then I am cool with that but it gets sold as the be all, end all solution to output consistency, which it doesn't seem to be.



Dec 18, 2011 at 01:00 PM
cgardner
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p.1 #12 · Why Color Profile?


Every engineered process a has some defined "nominal" performance level. In photography it is reproducing the same range of detail seen by eye with seen by eye color balance. The Catch-22 is that human perception is highly adaptable, both with regard to tonal range/contrast and color balance.

Color balance is itself a moving target in RGB. A D50/ 5000 K white on a monitor (AppleRGB / ColorMatchRGB) and D65/ 6500 K white (sRGB/AdobeRGB/ProPhotoRGB) both will be perceived as "pure" white individually when seen because the brain calibrates its perception based on observing known neutral content in scenes and images (e.g., a white shirt under a suit coat) and assuming are in fact neutral. In terms of RGB as percentage of total possible output on the monitor the "recipe" for a D50 white will have more R and G than the "cooler" D65 white. You could choose to calibrate your monitor to either one, and in doing so you calibration program, knowing the correct RGB "recipe" for D50 or D65 will adjust the linearity of RGB over the entire gray scale from white > black so all the grays, relative to each other, do in fact look neutral. But if you took a D50 calibrated monitor and put it next to a D65 calibrated one they wouldn't match, because they were calibrated to different color baselines.

In the early days of desktop color Macs and RadiusPressview monitor were calibrated to a D50/5000 K white to better match the viewing standards used in graphic arts at the time. I managed printing a web offset printing operation and we went to great expense to create standard viewing stations with 5000K light boxes and 5000K viewing booths where transparencies and proofs/production work can be viewed. Over the years D65 has become the accepted viewing standard for comparing print and screen, in part because of how the color spaces are defined and the monitors calibrated.

With regard to brightness, there are standards for setting up controlled viewing conditions for critical evaluation of proofing, down to the color of the paint on the viewing booth and the angle the print is viewed at to avoid glare. They form the "baseline" for adjusting monitor brightness level so the appearance of an image on screen matches the appearance of the print next to it IN THE STANDARD VIEWING CONDITIONS.

You likely don't have standard viewing conditions where you compare your prints to your monitor, which is one the reasons that shouldn't be your goal when calibrating your monitor. You should calibrate your monitor to the standard baseline, make some prints based on what you see from that standard baseline, then take those prints to where you plan to display them, put them on the wall and look at them critically.

If the display place is in a indoor room lit only by fluorescent light, such as your office at work the print will look different, in absolute terms, than if it hangs in an office brightly lit by a window. Here's where the Catch-22 of human perception comes into play. The perception color of the print will look similar in both lighting conditions because your brain will adapt your color perception. The brain will also adjust the pupil of the eyes to correctly expose the brighter tones. What you will find is that if the brightness level of the rooms are grossly different the perception of the mid-tone and shadows areas of the prints will change to some degree.

Working from the standard monitor calibration baseline you look at the print in the dark room, see it looks a bit dark in the midtones and know that relative to what looks "normal" on the calibrated monitor you will need to tweek the midtone contrast a bit lighter with the middle slider in levels, curves, or other contrast adjustments. In the brightly lit space if you observe the print looks a bit washed out and flat in the middle-tones and 1/4 tones you would make a similar correction from the "looks OK on screen" baseline, but in the opposite direction. So depending on where the print is located you'll wind up with a file for making the print which doesn't look "normal" on your monitor in order to make it look normal where it is viewed. The same is true for color. You may find a print will look better under some viewing conditions when the color is tweeked differently from what looks "normal" on screen.

By way of analogy it's like shooting a gun and aiming for the bulls eye but finding the bullet doesn't hit dead center due to the distance or wind from the baseline the gun was sighted in for x distance from target with no wind. So you simply adjust for distance and windage for wherever your target is the actual viewing conditions of your prints.





Dec 18, 2011 at 01:43 PM
theSuede
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p.1 #13 · Why Color Profile?


Hrow, it seems you're somehow missing something in the software included for profiling the monitors.

Most software packages have some kind of initial setup, where you can specify things like CCT (WB temp) and reference brightness and preferred gamma.

Even the cheapest heads can measure brightness differences down to a single percent at 100 cd/m (a few hundreths of an Ev!) with very repeatable accuracy. Often you get a moving target slider, that you're supposed to adjust by knobbing around with the hardware settings of your screens (unless you use a screen that actually HAS hardware calibration, in that case this is an automated step).

Since you're on Mac screens - that have miserable controls and very bad panel electronics - I'd suggest not fiddling around to much. Get close, and accept the results. I'd suggest somewhere between 5700-6000K WB temp and maybe 100-120cd/m. This is a compromise against the capabilities of your screens, and it will preserve them more "as they were". This gives better results for most screens with low tone-resolution in the panel driver.

Then you usually check the options "keep native WB" and "keep native brightness" for the PROFILING part of the operation.

You have mac screens. They are just about uncalibratable. Period. What you're doing is skipping most of the calibration, and getting straight at the PROFILING, which is half of the heavy lifting. This is where the measurement head runs through a lot of different colors and grayscales to record how your screens behave WITH THE SETTINGS YOU SET THEM TO EARLIER! The profiling software then has to generate correction curves for ramp nonlinearities in your screen, and what the color primaries are (which in turn tells it about absolute WB temp).

The correction curves go into the graphics driver, and the absolute color primaries and WB goes into the system as "just another color profile". This profile is exactly like sRGB or Adobe RGB, only "in reverse". In stead of telling the system that sRGB [R,G,B] means [XYZ] it contains information that the system uses to convert from [X,Y,Z] to the graphics card output.

This means that an Adobe RGB fully saturated green WILL NOT look exactly alike on the two screens! None of them can show an actual Adobe RGB green, but both will do their very best. But put up an Adobe RGB [60,255,60] and it sould look identical on both screens (if you set them both to the same maximum brightness value).

I've NEVER had really visible differences between two screens after calibration/profiling - unless I've used a head not compensated for wide gamut screens on a wide gamut screen. This is not your problem.



Dec 18, 2011 at 03:35 PM
Peter Figen
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p.1 #14 · Why Color Profile?


You're also dealing with device repeatability here, in trying to get two displays to match as closely as possible, or even calibrate to the same standard over and over again. There's a fairly in depth study of all the different calibration units on the market today that I read over at Luminous-Landscape, that seems to suggest that the single best unit on the market today is the BasicColor Discus followed closely by the new i1 Display Pro. Those too had both, simultaneously, the best repeatability, overall accuracy, and multi-unit consistency of all compared. Personally, I probably would not be using a ColorMunki for monitor calibration, or much else, for that matter. I think you're expecting too much of that particular device and need to consider higher end, specific devices for both monitor calibration and profiling and print measurement and profiling.


Dec 18, 2011 at 04:17 PM
richdavid
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p.1 #15 · Why Color Profile?


hrow:
I'm searching for a new color management system for my iMac and found this interesting page you might find insightful. The video is especially interesting I think.

http://www.robgalbraith.com/bins/content_page.asp?cid=7-11622-11688



Dec 18, 2011 at 04:49 PM
skibum5
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p.1 #16 · Why Color Profile?


Hrow wrote:
theSuede.

I realize that a print "brightness" will vary dependent on the viewing conditions.

Here's the problem... in the past, I have set-up my monitors using Apple's built-in calibration and compared them to printer output using the ICC profiles provided by the paper manufacturer. The prints closely approximate what I see on screen but some adjustments are necessary to get them closer. I have those adjustments set-up as an action that I run prior to printing.

Everyone I know keeps telling me that I need to calibrate my monitors - so I do. Now they are "officially" calibrated and both screens are
...Show more

they really shouldn't be ending up THAT radically different, especially not when you use the same probe on both and assuming both use reasonable similar backlighting/etc.




Dec 19, 2011 at 01:07 AM
skibum5
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p.1 #17 · Why Color Profile?


Hrow wrote:
Sorry if I'm being dense here so I'll ask the base question a different way....

If the screen brightness is variable in the calibration process, how does one consistently match the brightness of the image on screen to the print output brightness?



print brightness kinda depends whether you shine direct sunlight or a 20 watt bulb on it

prints have low contrast ratio so it's important to make use of the pure white paper color even moreso than it is for a screen image to hit near 255,255,255 often you need to add a bit of contrast before printing and something lower the white point a tad so the bright parts don't end up looking too dirty and washed out

you can do these before print edits in photoshop printer emulation mode to get a slightly better sense of things and maybe dial down brightness a bit closer to 80-90 cd/m^2 on the screen

there really is no such thing as brightness matching itself, since it's an ever changing target, you just want the contrast to look good on the limited contrast of paper and make sure to use enough of the top bright end of the paper

and avoid poor quality printer+paper .icc profiles



Dec 19, 2011 at 01:12 AM
Hrow
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p.1 #18 · Why Color Profile?


Thank you. I understand now and appreciate all of the thoughtful and lengthy responses to my question. . The component that I was missing was the relativity of the process to variable real world conditions as it is usually presented / sold as a "scientific" necessity. To me, a scientific process implies repeatable, constant results and that was the error of my ways. I did not factor in that "repeatable" and "constant" was also fluid.




Dec 19, 2011 at 12:57 PM
RustyBug
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p.1 #19 · Why Color Profile?


+1 @ relative

One other difference to remember is that one process of generating the luminance values is additive (monitor), the other is subtractive (print). The monitor will always be 'brighter' than ambient ... the print will always be 'darker' than ambient ... and your eye/brain will always be performing adaptive accomodation.

When I think about my ambient light level as X, then it is kind of an (monitor luminance)Y-X vs. an X-Z(print reflectance) kind of relationship between them.

Also, even if you can' t get you monitors to have equal lumination levels relative to each other, you can still gain a more neutral spectral (RGB) response between the two. I've got one LCD (HP ips) & one CRT (La Cie), that I use side by side. I can get the luminance levels pretty close, but not exact. I edit mostly off the LCD for easier viewing, but when I want to "soft proof" my print, I know that shifting to the lower luminance level of my CRT gives me a "relative" hint at what a print will be (i.e. darker) ... since my LCD is 'brighter' than my CRT.

When I remembered the additive vs. subtractive relationship relative to the ambient light levels ... the "light came on" for me as to why "picture lights" are used above wall art ... and I'm no longer chasing a ghost to get "matching" luminance levels to be the same between monitor vs. print. Rather, I cross-check with my numbers (objective) instead of my (subjectively adaptive) eyes for the dynamic range/values I want in the image ... KNOWING that the monitor vs. print can't, won't and aren't "supposed to be" a perfect match of luminance values ... under the SAME ambient levels.

The scientific aspect of "repeatable" and "constant" still apply ... it's the (errant) EXPECTATION that one process (additive) is EQUAL to the other process (subtractive) is the part that makes it seem "unscientific". The "fluid" part is the fact that you've changed processes for presenting the image to your eyes when you go from monitor to print ... i.e. Y-X vs. X-Z.


HTH


Edited on Dec 19, 2011 at 04:27 PM · View previous versions



Dec 19, 2011 at 03:28 PM
cgardner
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p.1 #20 · Why Color Profile?


Hrow wrote:
To me, a scientific process implies repeatable, constant results and that was the error of my ways. I did not factor in that "repeatable" and "constant" was also fluid.


There is that in the calibration process, but its just the starting baseline, not the end goal of the exercise.

For example of you religiously set Custom WB off a gray card and can manage to record a full range of detail at capture you will have a "nominal" baseline result out of camera and will not need to mess with it must. The camera becomes the baseline for "correct" color.

Shooting a subject holding the gray card after setting WB you can open it on screen. If you measure the card with the eye dropper the RGB values will be equal, confirming the nominal camera baseline of neutral color. If your monitor is correctly calibrated the card should also look gray on screen. But due to how adaptive color vision is your brain thinking it is gray because you set Custom WB from it and seeing R=G=B with the eye dropper will adapt your perception even if your monitor is slightly off.

That happens all the time. Someone will do a calibration, assume its perfect, but mess it up somehow resulting in the screen having a bias. They open a perfect photo out of camera, judge it by eye, and screw it up. That's where the gray card in a test shot is invaluable. You can open it, measure it, click on it to make R=G=B and have an objectively neutral starting point for your color. If for example your calibration is off and you open a file with the gray card and it seems a bit too warm, measuring the RGB values and finding them neutral will give you a clue the monitor is off. Trust the numbers, not your eyes.

Often technically neutral color might not convey the mood you want in the photo. Often you want a warmer or cooler vibe in portraits, depending on the mood of the subject you wish to convey. So you need to move off the nominal baseline, but ideally in some way you can objectively measure and judge. That's where color targets like the Macbeth are helpful.

This screen shot is of the camera profile section of ACR. When a camera is added to ACR Abobe recreates the preset styles for the camera:







What styles do is shift the color balances selectively WITHOUT AFFECTING GRAY BALANCE. For example here's a MacBeth chart with different styles applied. Note how the colors change but the gray column doesn't.







The reason it is important to keep neutral grays neutral is because when looking at a photo were you want the face a bit warmer than the camera captured it from the neutral baseline the viewer of the photo will still expect the white sweater to be white, not yellow.

In my workflow I open the test shot like the one above with the card target and tweek the color in the styles tab where I can adjust color without affecting the overall gray balance with the presets and slider adjustments. Then I copy/paste that adjustment to the other files in the batch. The color chart in the test shot makes it easier to see how the adjustment is shifting the color hue and saturation from the neutral baseline. So in that sense color is a moving target and the goal isn't making it neutral, its making it look good by eye.

After making the adjustment to the test file with the target if I make a test print from it before starting any other editing I'm able to see how it will change when printed. I don't expect it to exactly match the monitor, I just want it to look "normal" and "real" in the lighting were it is viewed. Starting with a file out of camera which has Custom WB and a full range of tone pretty much assures the print will look OK because that's how the process is engineered to work. The only things to screw it up are: 1) operator error; 2) inaccurate profile for printer/paper, or; 3) mechanical problem.

All prints have two things in common: white paper and solid CYMK ink. It's what happens in the middle that affects the overall perception of the photo. That's can be controlled with the middle slider in Levels. If a file overall looks darker when printed than on screen the solution isn't to make the max. black lighter, its to make the midtones lighter. A simple way to do that I open the file in Levels and move the middle slider left....

This is baseline nominal file on screen, but it will print darker...





Knowing that I will make a Levels tweek before printing to open the midtones to compensate for the "dot gain"...





The net result is that the lighter screen file when printed is a closer match to the "nominal" screen file.

When I edit files for screen display and prints I wind up with four copies of the file: 1) the camera RAW; 2) a "Master Edit" copy; 3) copies reduced and sharpened for screen display; and 4) copies resized, adjusted and sharpened for each print size. That might seem like overkill, but its necessary to account for the differences in output methods if optimum results are desired.














Dec 19, 2011 at 04:18 PM
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