Re: Optical/Spider black and white target points?
Re: Optical/Spider black and white target points?
- Subject: Re: Optical/Spider black and white target points?
- From: "Russell Proulx" <email@hidden>
- Date: Mon, 29 Sep 2003 10:30:32 -0400
- Priority: normal
On 29 Sep 2003 at 7:48, Roger Breton wrote:
>
I think you want to set as low as you possibly can. The lower you set it the
>
higher the Luminance Ratio (from white to black). 0.30 is by all means a
>
very satisfactory setting if you feel you can achieve it reliably.
I suspect the answer has something to do with the ambient lighting
conditions. In an fairly bright production/office environment one would
probably have to set the black point higher to be able to achieve shadow
separation. I work in a darkened room with one small desk lamp illuminating
an area of a white beside me and thus am much more sensitive to the shadow
details on my screen. This is probably why I can go so much lower with my
black point. So... is there a limit to 'how low I can go'?
>
quoting from ISO-12646, Section 4.8, "The luminance level should be
>
as high as practical but shall be at least 80 Cd/m2 and should be at least
>
120 Cd/m2". Why the two specifications? I don't know.
Can we therefore assume that 'higher than 80 is preferred' (since it's
presented as a 'minimum') and something closer to 90 would be better. Is
there a reference one should use to determine how high one can/should go?
(and....)
On 29 Sep 2003 at 9:49, Herbert GIBSON wrote:
>
General recommendation for White seems to be ~85. 80 - 90 I'd be
>
happy. This lower value helps match reflected white from inkjet paper.
>
People use values up to 130 - they're nuts! Reportedly really low
>
values cause loss of gamut.
That sounds like good advice.
I teach a Photoshop class as part of a professional photography course.
Students ask "why" and I'm trying to get answers to what seem like simple
questions. But when I check the various 'authoritative sources' I get
somewhat different (perhaps vague is a better word) answers. The "why does
a .30 shadow setting result in a black setting that looks too bright?"
needed answering. I think you've both answered that pretty well. Thanks:-)
I'll recommend that one use the target supplied by the Colorsync
calibration utility or the one included in Precal for those who own that
software. This will set the black point necessary for the environment the
monitor is in.
The white point setting info (contrast) still seems a bit less scientific
than I would like. Sounds like "anything over 80 is good, higher is better
if that's what you prefer". Should it be set higher in a brighter work area
the achieve the "luminance ratio that is a least 100:1" as quoted in Roger
Breton's reply?
Thanks for the help!
Russell Proulx
Montreal, CANADA
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