Re: Lighting question: Illuminance? (RWCM)
Re: Lighting question: Illuminance? (RWCM)
- Subject: Re: Lighting question: Illuminance? (RWCM)
- From: Chris Murphy <email@hidden>
- Date: Fri, 23 Jan 2004 15:18:29 -0700
On Jan 22, 2004, at 4:06 AM, Peter Karp wrote:
Hi,
this posting is addressed mainly to the authors of RWCM, but I'm
interested to hear any comments :-)
I begin to wonder what illumance is "ideal" for proof/softproof
comparisons and/or for working with digital images. In germany the
FOGRA
suggests 2000 lux (like specified in ISO 3664) for color critical
comparisons. This would mean that a display would have a similar
brightness when the luminance of the display is about 600 cd/m^2. As
it's
important to match the brightness of the display and the viewing booth
--
and no display for prepress/photographers I'm aware of offers such a
high
luminance -- I wonder which illuminance should _today_ in practice be
used?
The main point is that you're not going to get a correlation between
display and viewing conditions if you follow ISO 3664. You'll have to
make the adjustment mentally recognizing that under "practical
appraisal" of 500 lux viewing prints will be brighter and more
saturated than the display. When viewing under "critical comparison" of
2000 lux viewing prints will be a whole lot brighter and a lot more
saturated than the display, as well as having more contrast.
On page 210 in Real World Color Management it's stated that
the ISO-Standard wasn't created with monitor-to-print machtings in
mind. The ambient illumination for color monitors should be less or
equal to 32 lux and _must_ be less than or equal to 64 lux. For
monitor print matching, all these values would be too high.
1) "These values are way too high" refers to the ISO recommendations or
to the low illumance values of about 50 lux?
That's a good question, and I've marked it for clarification. The
second sentence about ambient illumination is found in ISO 3664. The
third sentence is our comment, but it's not clear what values we think
are too high. The values we're referring to are those for practical
appraisal and critical comparison are too high:
1. compared to the capability of displays.
2. such a viewing light source would increase the ambient illumination
beyond 64 lux.
So we bring up the ISO spec as a matter of reference but then point out
that it's not very practical if you're going to have a monitor in the
same vicinity as the viewing box. You can't have both 500 lux or 2000
lux viewing and also have a monitor in the same room and expect things
to work.
2) Why should an illumance be below 64 lux in all cases? Is this
recommendation only for the ambient light or for the proof light?
Ambient light for the room in which the color monitor used for editing
is placed. I don't know how they came up with 64 lux really. Maybe it
was based on data for CRTs for which 85 cd/m^2 was pushing it. CRTs
today are brighter. I think 64 lux is not a whole lot of light. You
want it low enough because monitors aren't that bright, but then also
you want it high enough that people aren't calling in sick days because
they don't want to work in a dungeon every day.
Which illuminance would you suggest for the ambient light and for the
light in a viewing booth (and why)?
That's on page 214 :) Basically you want an adjustable viewing box and
pair its brightness down to match that of the monitor.
Chris Murphy
Color Remedies (TM)
www.colorremedies.com/realworldcolor
---------------------------------------------------------
Co-author "Real World Color Management"
Published by PeachPit Press (ISBN 0-201-77340-6)
_______________________________________________
colorsync-users mailing list | email@hidden
Help/Unsubscribe/Archives:
http://www.lists.apple.com/mailman/listinfo/colorsync-users
Do not post admin requests to the list. They will be ignored.