Need for visual verification : adventures in color/colour correction land: Eizo, x-rite i1 +intel

Started 7 months ago | Discussions
itsastickup
Regular MemberPosts: 279Gear list
Like?
Need for visual verification : adventures in color/colour correction land: Eizo, x-rite i1 +intel
7 months ago

I thought I would briefly write up a problem I had calibrating my screen to save future persons from this trouble, but also to highlight the need to visually verify calibration with onscreen visual guide pics. Googling I found no info on the specific problem I had (which I think is an intel video driver issue), and I suspect that because people are not using onscreen visual guides to verify, they don't realise that they have a problem.

In the past I've simply calibrated using my Spyder 2 device and trusted the result.

But in this case I had bumped up against this visual verification page:

http://www.lagom.nl/lcd-test/all_tests.php

and after using my x-write device found that things were not right if I followed the usual instructions.

The main calibration instruction that made a mess of my results was to "set the graphics card driver software to its defaults". I should mention that this was on the Intel mobile 4 Series express chipset on an Eizo FS2333 IPS screen (Review here). Those defaults are likely fine for the laptop's screen, but not good for external screens.

I reset to the defaults, and then followed the x-write instruction adjusting my screen via its OSD menus to adjust RGB gains, brightness, contrast etc as needed.

There were four problems that the resulting calibration profile produced. Using that web site I could see :

1)the gamma was way out (target 2.2)

2)more than half the contrast checkerboards were not visible (as was obvious just looking at pics which visually had blown highlights galore)

3)the x-write software reported a resulting temperature of 6750K instead of 6500 (selected D65 as target), and general accuracy was reported as somewhat out also (in contradiction of that prad.de review which shows this screen to be accurate enough for semi-pro photography).

4)almost half the blackpoints where not visible.

I tried endless permutations, including eventually adjusting the graphics card away from its defaults. Different driver version were to no avail.

Finally, I hit upon the solution.

I had to find a balance between the graphics card settings (in which it was necessary to adjust both gamma and contrast, to .9 and 40 respectively, likely intel specific) and also the screen's own setting, to a gamma of 1.8. The combo of the two conflicting gammas, neither at their defaults, is what finally got me the closest to a good result.

As it happens, the contrast is still two high on the graphics card, but I can't put it lower than 40. I'm missing just one contrast checkerboard and one blackpoint (here I am assuming that 255 and 0 are meant to be non-visible anyway, so it was 254 and 2 that should have been visible but were not). I think that this is acceptable.

The temperature is now 6476, which is close enough I think, and the gamma is just about right, very slightly off.

I'm still not so pleased with the result since it's evident that the contrast is still something of an issue. Both darker blackpoints and lighter checkboards are very hard to see. You might think that that is to be expected. But when I'm watching DVDs, the darks are blocked up, which is not the case on a TV.

Anyway, the moral of this tale of woe for me is to try out a Radeon or ATI based laptop next time.

-- hide signature --

Dpreview Auto image-resizer for Firefox :
http://userscripts.org/scripts/show/105066
Chrome version here:
http://userscripts.org/scripts/show/105067

 itsastickup's gear list:itsastickup's gear list
Nikon D5100 Fujifilm X-Pro1 Nikon AF-S DX Nikkor 35mm f/1.8G Sigma 10-20mm F4-5.6 EX DC HSM Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR +4 more
itsastickup
Regular MemberPosts: 279Gear list
Like?
Re: Need for visual verification
In reply to itsastickup, 7 months ago

correction, those blackpoint and checkerboard numbers are slightly different on the visual verification guide; the main point being that I seem to be missing one of each where the prad.de review shows them present (it even looks like they may be using the same guide).

-- hide signature --

Dpreview Auto image-resizer for Firefox :
http://userscripts.org/scripts/show/105066
Chrome version here:
http://userscripts.org/scripts/show/105067

 itsastickup's gear list:itsastickup's gear list
Nikon D5100 Fujifilm X-Pro1 Nikon AF-S DX Nikkor 35mm f/1.8G Sigma 10-20mm F4-5.6 EX DC HSM Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR +4 more
Reply   Reply with quote   Complain
itsastickup
Regular MemberPosts: 279Gear list
Like?
Need for visual verification : adventures in color/colour correction land: Eizo, x-rite i1 +intel
In reply to itsastickup, 7 months ago

hmmm, maybe the mods could correct the subject to "Need for visual verification : adventures in calibration land: Eizo, x-rite i1 +intel"

-- hide signature --

Dpreview Auto image-resizer for Firefox :
http://userscripts.org/scripts/show/105066
Chrome version here:
http://userscripts.org/scripts/show/105067

 itsastickup's gear list:itsastickup's gear list
Nikon D5100 Fujifilm X-Pro1 Nikon AF-S DX Nikkor 35mm f/1.8G Sigma 10-20mm F4-5.6 EX DC HSM Nikon AF-S DX Nikkor 55-300mm f/4.5-5.6G ED VR +4 more
Reply   Reply with quote   Complain
technoid
Senior MemberPosts: 1,295
Like?
Re: Need for visual verification : adventures in color/colour correction land:
In reply to itsastickup, 7 months ago

This problem illustrates an issue with monitor profiling. There are two techniques commonly used. One is to set the video controllers gamma conversion table to comp for the requested gamma (usually 2.2) and use a matrix conversion with RGB coordinates for color. The other is to use an unmodified table (ie, a one to one) and have the profile adjust the color and gamma based on a 3D lookup similar to the way printer profiles operate.

The former has the advantage of looking pretty good with non color aware apps like most all browsers. The latter produces better results with color managed apps since a one to one gain mapping produces less banding but much worse results with non color managed apps.

A Third approach is to use a monitor that does all the corrections internally to the monitor. Eizo photo monitors do this. This produces optimal results with both unmanaged and managed apps and always uses a one to one gains on the video controllers output luts. That's what I use. I have both wide gamut and sRGB target profiles set up on the Eizo but use the sRGB profile for all apps except things like photoshop on the infrequent occasion where sRGB is not sufficient.

Reply   Reply with quote   Complain
Keyboard shortcuts:
FForum MMy threads