Ambient correction
Ambient correction
Hi Andrew,
All major
display calibrator vendors (all two of us) are offering some form of
ambient correction.
Maybe a bit OT but it would be useful to discuss this more.
I think that it is a matter of intent. First let me say, I do not
believe that Scotopic adaptation is an issue here. I think that it has
more to do with small/field vs large field viewing conditions
If we immerse ourselves in darkness, we will scotpically adapt, but if
you have bright lights in a dark field, I do not think that Scotopic
adaption is really in play. In the presense of total darkness and
bright point sources we have very keen discrimination of hue. You can
prove this to your self by walking outside at night and looking a lights
and the stars and planets. There is certainly no chromatic adaptation,
all the sources generally have an obvious hue. Mars looks redish in the
sky, venus looks green. This is foveal vision and it is about as
"absolute" as it gets in human terms. As the ambient is increased the
peripherial sensors in the eye are now affected and they in turn, affect
our entire visual process as well. The foveal region of the eye
accounts for about 2 degrees of field but is responsible for
approximately 50% of our visual cortex activity in the brain. As the
ambient goes up the wide field off -axis receptors get into the act and
then we start the adaptation process. It is very rapid from dark to
light and relatively slow from light to dark.
. Remember that we have 2 degree color matching functions and 10 degree
color matching functions. Fundamentally as overall surround luminance
increases images appear more saturated and contrasty. The goal for most
ambient correction is to offeset this as best as possible.
Realistically this can only really work if the white on the display is
capable of exceeding the paper white. There has been some published
work that when matching whites on a display, the 10 degree color
matching function response should be used. This does make a lot of
sense, although we are not doing that yet. I would not say that ambient
correction necessarily gurantees a better screen to print match. If
that is your goal, then some very careful visual set up is necessary.
There is a lot of work that needs to be done in this area. Now that we
have displays capable of 300 - 500 nit luminances, it becomes more
important, because viewing at these luminances requires high ambient.
I'm no longer involved in that work, but we do have some researchers
looking at the issue far more critically than I did.
Regards,
Tom
Andrew Rodney wrote:
On 4/20/08 12:27 PM, "email@hidden" wrote:
All major
display calibrator vendors (all two of us) are offering some form of
ambient correction.
Maybe a bit OT but it would be useful to discuss this more. My understanding
is, what you're telling us is whether its too bright an ambient condition
based on a fairly old ISO spec?
Would there be some usefulness to measuring the light box and having the
software recommend a target luminance (and perhaps white point)?
I'm under the impression from another color geek who designs high end
display systems that you really can't have the ambient light too low, unless
its endangering yourself because the black of the display is affected by any
ambient light and hence that affects the contrast ratio perceived by the
user.
When you say "ambient correction" is this indeed a correction? If so, what?
Andrew Rodney
http://www.digitaldog.net/
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