Friday, July 12, 2013

Some notes on monitor calibration software

Last week I was at a customer's site calibrating monitors and because it was before midday the colourist wasn't there. So - knowing that in the past I'd set the white point on their displays to 80Cd/m2 and 6504k (as per BBC spec!) I balanced them thus.
Later in the day I got a very heated message from the production manager; the colourist wasn't happy and he wanted me back in there to match the Sony BVM to his 55" plasma "...which looks a lot better - much closer to correct". I asked him what standard he wanted the Sony set to and of course he had no idea.
Also - I've had a few people getting very excited about VirtualForge by SpectraCal; it's a test signal generator for a Mac with SDi o/p. The trick is that it talks over the network to their other product CalMan which can talk to the various USB-attached photometers (the XRite etc). They make great play of the fact that this in now a closed-loop where the test patterns can be changed automatically by the probe software. Presumably it still has to tell you what adjustments to make to the display and so how that is any better than you looking at the measurement and make the changes is beyond me.
It makes sense if you have a Sony probe attached to a Sony monitor - the monitor cycles though the various test patterns and reads the probe; it then tweaks the monitor's settings and you hopefully wind up with a properly calibrated displays. Having to have two computers and two bits of software (as well as a network) seems convoluted.
I'll stick with my trustee PM5639s (I have LCD and CRT probes for them) and the occasional hire of a PhotoResearch PR655 when I really need a spectralradiometer over a photometer.

  • Test signals for monitor calibration aren't hard - 10% gray, 50% grey, 100% peak white, various saturated colour fields, 100% bars and PLUGE allow you to do anything to a monitor that doesn't need the covers taking off and you getting down to component level.
  • Cheap USB photometers that claim to cover different display technologies are plain wrong; LCDs, CRTs, Plasma and OLED all have different metamerisms - a spectralradiometer is the only gadget that is display-technology agnostic.
  • Computer monitors and TVs are not grading displays - the MacBook Pro that I'm typing this on is calibrated using Apple's colour tool to D65 but when I point the PM5639 at it the colour temperature is 7340k at 220Cd/m2 (how wrong can it be for grading work?!)
  • LUTs can only decrease the dynamic range of a display device - never improve it. The best thing is to get the display calibrated before you start applying LUTs (and then only to simulate the look of a film stock etc).

Colour calibration isn't hard, but it requires understanding the nature of colour and vision and not just spending $395 on a bit of software.
Oh - BTW I carry all my test signals around on a little BlackMagic Hyperdeck. It's battery powered, fits in my rucksack and does proper 709 colour space between it's HD/SDi and HDMI outputs.

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