[Tig] D-Cinema Suite contd.

Stan Chayka schayka
Sat Mar 8 15:12:17 GMT 2003

I have received several private postings to the questions regarding the
possible use of a large screen viewing system in a color correction suite.

One particular response brings up a new question.  Here is the statement
made in quotes.

"We played with a "match" to a CRT, but then you still fight the fact that
image size plays a big role in how the colorist sees an overall image. This
factor alone will determine how much to boost black levels due to bright
objects in the general proximity. "

I used to evaluate this aberration of the viewing system when calibrating
CRT monitors for their black level utilizing the 'PLUGE' component of SMPTE
color bars.

The test was quite simple and revealed a certain flaw in the resultant

Try this yourself if you can.

Display color bars with pluge and determine that your point of extinction is
as you expect it to be. Hopefully correct.

Now place a box wipe to 10%black around the pluge only so that the color
bars are obscured.

Did the pluge appear to dive into the black?

If your answer is YES then there are 2 reasons that can cause this.

The first is that your monitor does not hold its' 'Clamping' adequately to
keep the blacks at a fixed level. To determine if this is the case, adjust
the black background up and down a little (+/- 10%) and see if the pluge
changes visual level. it shouldn't.

The other cause is more insidious. The image of the color bars is reflecting
inside the crt bottle and adding a flare-like error to the pluge. This is an
optical effect that may be what is being referenced in the above quote.

Can anybody who has access to a projection system try this same test and
report the results?

Again, private responses are also welcome.  I will share what I find out
with the group without causing anybody any public exposure.

Stan Chayka
President, NextGen Associates Inc

schayka at nextgen-assoc.com

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