LCD calibration/profiling

[Hendrik]

Well I finally took the step (leap) and bought a LCD screen for photo editing. My money tree in the garden is still fruitless, so I had to buy a cheaper model compared to the Eizo $1500+ models. I have read many reviews and searched many forums and decided the Samsung 215TW (S-VPA) was a good choice for 425 euros. It’s a model discontinued in the Netherlands, so I was a bit lucky.

My first impression is good. Full HD trailers looked amazing on the default settings. My ‘old’ screen is an 17 inch CRT, so the extra space was very welcome.

I tried to calibrate the LCD with my Monaco Optix XR Pro software and DTP-94 colorimeter. Determining the correct contrast/brightness settings is a bit difficult. At this moment I have Brightness: 22; Contrast 67 and this gives me a whitepoint of 130cd/m^2 and blackpoint of 0,16cd/m^2. My guide was a printer-ramp file and choose a setting I just could see all gray values from RGB 1,1,1 up to RGB 254, 254, 254, this means no clipping at the black and white end. For the rest native color temp and gamma 2.2

Profiling. First try was (with slightly different calibration settings at this point) creating a Table-based 3D profile (60% gamut compression), 99-patches; since this is recommended for LCD screens. After this an evaluation and the results disappointed me. I got high deltaE values in the 2-3 range and a few much higher with the yellow color giving me a deltaE of 11 (!). I know the evaluation process is only to determine a drift over time, and not a measurement of profile quality, but it disturbed me nevertheless. The black-to-white gradient showed me steps from black to white.

I tried a few more contrast/brightness adjustments, but the high deltaE did not change. Finally I tried the normal non-table-based profile and this gave me a much better deltaE, with a maximum of 2.8.

Problem with all this is how do you know the profile is accurate and you can trust your eyes during color correction?

I have a few questions:

The screen has a few pre-sets with the names: Text, Internet, Games, Movies and Custom. The custom setting is what I use now, but can I use the other settings when I e.g. play a game and return to my Custom setting when I have to work again? … or would this influence the colors?

Any comments on the above, is this the way I should profile my display? I’m still a bit nervous and are tempted to use my trustworthy 17-inch CRT again.  

[Scott Martin]

Determining the correct contrast/brightness settings is a bit difficult.

Very true. With any LCD monitor the Contrast and RGB settings must be left at their native settings. You can usually return to the native settings by selecting an option called "Reset to factory defaults" or something similar. Generally speaking, native contrast settings are usually 50, 75 or 80 and native RGB settings are usually 50 or 100 depending on the make and model. I've thought about making a spreadsheet but jeez, one has to have a life too.

The only hardware control that one ever should adjust is brightness that affects white luminosity. In fact, LCD monitors should only have a brightness control! Apple has the right thinking offering only brightness on their cinema displays. Dell is now doing the same thing on their larger WFP models and I hope others follow this trend. Figuring out what a monitor's native contrast and RGB settings are is a pain that users should not have to bother with. Anyway, adjust your brightness to get the desired white point luminance and doing be afraid to crank it down to 0 if necessary.

The presets you are speaking of change the contrast, brightness and RGB settings. Choose "native" or "custom" and set contrast and RGB to their native settings.

[jackbingham]

Scott, we clearly need that spreadsheet. Wait a while for a life! Couple of things. Noting where the monitor places the rgb sliders on reset is important. In general if the rgbs reset to 50% that is max white brightness. So if you adjust those sliders upward the white point will not change but the midtones and shadows will continue. Those reset values should be considered the absolute top. I'm not sure I'm with you on not being afraid to go all the way to zero on lcds. I've noticed some consistently increasing errors in validations with some monitors at zero. I would suggest staying above 10%, but that is just what I've seen.
No doubt we are dealing with a series of compromises here. Video cards are only 8 bit, you can't change the back light color and the color controls on some monitors are better than others. You can choose native but not if you care about critical print matching under controlled viewing conditions. Somewhere in the middle is a trade off between banding, which I think we are seeing less and less as the calibration applications improve, and color matching.
One more point. I think it's swell that monitors are shipping with max brightness of 400 to 500 so they might last a bit longer. But not being able to manually dim them down to a reasonable level so you aren't forced to do it in the card is silly.

[Hendrik]

The RGB channels are untouched and at 50%. I've always learned that native color temp is the only way to prevent reducing the 256 luminance steps of the RGB channels. It's now between 6700 to 8200K (blacks are cooler) and therefore a bit cold.  

I think it's acceptable to change the contrast on LCD screens. You only change the luminance, but a little bit different. It's a mystery to me what exactly changes, that's a secret laying at Samsung.

I always thought 3D Table-Based profiles were preferred with LCD screens, but it seems I get better results with the ‘normal’ profiles.  

[Scott Martin]

The RGB channels are untouched and at 50%. I've always learned that native color temp is the only way to prevent reducing the 256 luminance steps of the RGB channels. It's now between 6700 to 8200K (blacks are cooler) and therefore a bit cold.[a href=\"index.php?act=findpost&pid=139559\"][{POST_SNAPBACK}][/a]

In my option, it is better to sacrifice some of those 256 shades to have matching paper and monitor whites, especially when the native white point is hideously cool. It's hard to look at cool highlights and then get printed highlights that are much warmer - that kind of defeats the purpose of dispaly calibration. I feel that photographers value an excellent match over perfect gradations. There are different philosophies here and it's OK to disagree.

I think it's acceptable to change the contrast on LCD screens. You only change the luminance, but a little bit different. It's a mystery to me what exactly changes, that's a secret laying at Samsung.[a href=\"index.php?act=findpost&pid=139559\"][{POST_SNAPBACK}][/a]

Changing the contrast can result in a completely uncalibrateable (is that a word?) display. If you set the contrast too high the extreme highlight and shadow detail blows out and there is nothing the software can do to bring that back acceptably. Bring up a good evaluation image and play with the contrast to get a feel for what is going on. Again, the behavior is different for different brands.

In general if the rgbs reset to 50% that is max white brightness. [a href=\"index.php?act=findpost&pid=139553\"][{POST_SNAPBACK}][/a]

A fair amount of Dell's use 75% as their native and a few others use 80% or 100%. If you crank them down to 50 you will get a significantly reduced white luminance and bit depth.

I always thought 3D Table-Based profiles were preferred with LCD screens, but it seems I get better results with the ‘normal’ profiles.  [a href=\"index.php?act=findpost&pid=139559\"][{POST_SNAPBACK}][/a]

Right, 16bit LUT based profiles without gamut compression are almost always the way to go on LCDs.

BTW, now that you are getting the process down on your new LCD you really should give Color Eyes Display Pro another chance. :-] The white point tuning feature, when used delicately, is an excellent way to tweak your display's white temperature for perfect paper white matching. Even when you do so, with this software I think you will be surprised how smooth the gradations are. This demonstrates a good example of when the theory and real world experience don't line up.

[Hendrik]

I shall give Color Eyes another try.

I'm still indecisive I keep the display. I really like the format and resolution (1680 x 1050). I come from a 17-inch CRT, so this feels BIG.

I don't like the uneven illumination across the screen. With a gray background I measure a luminance difference of 2 cd/m^2 between the left and right side of the screen. It doesn’t sound much, but I can see it clearly.

Is this normal for LCD screens? If this falls in the normal range, I have to get used to it. I know I should not compare it to CRT screens.

[feppe]

I also have the 215TW and love it. It's perhaps best bang for the buck in the sub-24" widescreen range suitable for photo editing (true PVA panel with enough true bits).

I use Spyder2 for calibration, and it works wonderfully. Don't worry about the cinema etc. settings, they won't mess up your custom settings.

My 215TW has brightness anomalies in each corner, which is only visible on a uniform dark background. Can't notice it in normal use even if I try.