Color space and LCDs

[Gints Klimanis]

Hi,

I'd like to use an LCD for video monitoring. Motion response aside, do I have to worry about color spaces ? The monitor calibration units such as Gretag MacBeth handle sRGB, so how do I do 601 or 709 ?

Thanks,

[Glenn Chan]

I believe sRGB and Rec. 709 have the same primaries (chromaticity of the "phosphors" in a display/color of the R/G/B colors). Then there are SMPTE C primaries and EBU primaries... they relate to SD work, for the NTSC and PAL worlds.

2- I don't believe the Gretag will do that much about the primaries of your monitor for VIDEO work, since most video applications don't/can't implement the requisite color management.

[Gints Klimanis]

Thank you for the detailed information Glenn. Your work on the VASST Vegas training DVDs looks very useful.

For LCDs, I'm looking at the NEC Spectraview 2190 and 2090, both of which offer calibration in the monitor itself via color lookup table adjustment.
While those LCD monitors may be premature in covering the NTSC colorspace, some of the newer wide-gamut LCDs by NEC (2180WG-LED)
seem to be able to cover 100% of the NTSC color space.

I've grown accustomed to nearly automatic color calibration of CRTs and LCDs for the computer industry with products such as the Gretag Macbeth EyeOne Display2 hardware calibration devices. Is there a reason that such devices are unable to work on interlaced video displays?

[Glenn Chan]

Btw, the DVD doesn't have very much information on color management... it talks more about color correction/enhancement techniques.

2- The Adobe RGB color space:
In an early version of Photoshop, there was a "SMPTE" color space that followed the old (and unused) NTSC color space- the original intended color space when NTSC set the NTSC television standard. NTSC color space was quite wide gamut, and you couldn't design TVs to be very bright and have wide gamut. Most TVs that subsequently came out didn't have very wide gamut. Eventually Conrac monitors became popular as broadcast reference monitors, and their phosphor chromaticities (i.e. color) got adopted as the standard color I believe (SMPTE C).

Anyways, the reason behind Adobe RGB color space was that they screwed up and used the old disused NTSC color space instead of SMPTE C (the original intent). However, they simply couldn't just change the numbers around to the correct ones... so they renamed the color space to Adobe RGB. And that's the story behind Adobe RGB (according to Charles Poynton anyways, who pointed out the error to Adobe).

3- Having a wide gamut monitor is not useful, unless you have some form of color management in place. In video, the standard practice is a very rudimentary form of color management.

If you get a broadcast-grade monitor with the exact primary color chromaticities (i.e. the exact colors) of the relevant standard, then you're set. You just need to calibrate the monitor (unfortunately the calibration controls are weak, so this ain't perfect).

For film-out work, they have specialised 3D LUT solutions which typically cost tens of thousands of dollars.

But anyways, you could theoretically use a wide-gamut monitor and then use color management so it has the right color. However, the program would have to do this with reasonable performance. To get good quality (i.e. 8-bit or 10-bit LUT instead of 6/7-bit or 2D instead of 3D LUTs) AND good performance costs $$$. For video output, it's just easier to get a monitor with the right chromaticities.

Right now, the HD standard is supposed to be Rec. 709 while in practice most high-end work is done in reference to SMPTE C. Some monitors don't get that close to the standards (i.e. some of the lower-quality broadcast monitors out there, LCD and CRTs with P22 phosphors).

I've grown accustomed to nearly automatic color calibration of CRTs and LCDs for the computer industry with products such as the Gretag Macbeth EyeOne Display2 hardware calibration devices.

The cheaper color calibration devices may not work that well due to metamerism... which causes inaccuracies.

4- Some NLEs don't display the real deal on their video preview (on the computer monitors). So external monitoring via a broadcast video monitor can be a better idea.


Does that make sense?

[Gints Klimanis]

Thanks for the thorough explanation, Glenn. After reading your post, I guess I shouldn't be expecting any changes in the near future, but I wanted to see if my near-term LCD purchase would at least do the proper color space.