Datacolor User to User Support Group.

--- In colorvision_group@yahoogroups.com, "esimanor" <esimanor@...> 
wrote:

> 
> But here is a crucial issue, I think:
> 
> i am glad to read that there is such a thing as a standard luminance 
> unit (candela). But how on earth do your Brightness and Contrast 
> adjustments on your screen relate to this?? Is there any clear 
> corellation between 1% change in Brightness and the increase of your 
> black point by such and such candelas?! what about contrast?
> 
> Plus here is another critical point: what exactly is your Brightness 
> and your Contrast adjustment knobs doing to your black and white 
> point on an LCD screen? I read somewhere that an LCD can only offer 
> one adjustment, which is the backlight of the display (most likely 
to 
> affect only your black level (brightness?), I would have thought)?.
..
> 
> Now, the factory settings on my LCD (NEC multisync 1980 FXi) are 
> as assumed Brightness: 100% and Contrast: 50% but this gives a very 
> high black level indeed (too high )! Plus, i work with agencies in 
> europe to whom I send processed files. most of these agencies still 
> use CRT's which tend to be naturaly "darker" than LCD's. Could i 
> possibly ask them to measure the luminance of there black and white 
> point and try to "copy" them on my screen before calibrating? how 
> would i go about this? Ideally they would provide me with a measure 
> in candela for each point and i would feed it to my software, or I 
> would be able to establish a corellation between the candela values 
> and my settings?...
>
I may be completely wrong here but I think you are getting the wrong 
end of the stick about the purpose of this device. I don't think it is 
ever intended to match the illumination levels between monitors or any 
other viewing system, just give the same appearance of colour. Also I 
think you have the terms a little mixed up. My understanding of 
brightness, as a control, is that it adds or subtracts a constant 
value from the value of each pixel but the overall luminance of a 
pixel depends on the source of the light, be it backlight, CRT 
phosphor, or 10kW projector lamp. Contrast, as a control, affects the 
steepness of the curve that relates pixel values to screen brightness 
values. It should not affect the black or white point.

Again, I may be completely wrong, but I think it is unreasonable to 
expect to match the actual illumination levels of your monitor and 
your client's. All you can expect to do is both be able to see the 
same shadow and highlight detail and perceive the same colours. 
Presumably your client's screen is not the end use for your images. If 
they are going to be ending up as print then the illumination levels 
are meaningless anyway.