[argyllcms] Re: Tests with DTP92 on video-projector
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 07 Apr 2006 01:42:34 +1000
Frédéric wrote:
The DTP is rated up to 500cd/m^2 (that's the Y value).
L value in Lab space also give luminance, so L=100 means 500cd/m2 ?
L*a*b* is most often a relative measure. The L is (by definition)
100 at the white point. Often, XYZ is used the same way, with
Y = 100 (or Y = 1.0 by ICC custom), at the white point,
but when measuring emissive devices, there is no known limit to
the white point, the way there is with reflective or transmission
measurement, where 100% light reflection/transmission is the most
you can get, so some form of absolute measurement reading is
needed for emissive devices. The common approach, is to use
XYZ, where the Y value is in cd/m^2.
Once the white point of the device has been established, the
test chart values can be converted to relative color values.
Someone suggested to use a lens, and blur it with glass paper. This way,
focusing and diffuser could be the same stuff...
Yes, exactly the same idea.
Graeme Gill.
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