[tig] printer points exposure and ire:

Marc Wielage mfw
Sat Sep 4 04:41:37 BST 2004


On 9/2/04 6:02 PM, "Dominic Case" <cased at atlab.com.au> wrote on the TIG
list:

> Executive summary for cinematographers: 1 stop is 7 printer points. But it's
> not that simple. Read on...
>--------------------------------snip----------------------------------<

I translate a printer point to IRE very un-scientifically:  as "a little
bit."

If the client wants something slightly warmer, I add maybe 2-3 more units of
red to the overall gain (white level), and tell them "that's a point or two
of red."  Or if they want it a tiny bit darker, I'll drop the overall level
maybe 2-3 units and say, "that's another point of density."

Judging by exposure tests I've seen, I'd say a stop (7 points) is much more
radical, like maybe 20 units.  As Dominic Case says elsewhere, a change in
exposure alters mid-tones, blacks and gain, so it's not easily translatable
to a waveform monitor.

Every DP I've ever worked with seems satisfied with that explanation, though
it's not very scientific.  Would that we had a meter that could read out in
printer points right in the telecine bay.

I believe there is a way to correlate histograms and other computer-based
techniques to digitally color-time pictures and translate the adjustments to
precise printer points.  But so far, I know of no way to do that in real
time on a conventional color corrector like a Pogle or daVinci.

Of course, this is strictly my opinion.  Dominic is far too modest to
mention his terrific book:

FILM TECHNOLOGY IN POST PRODUCTION (2nd edition)
by Dominic Case  
224 pages/paperback
Published by Focal Press (August 2001 -  ISBN 0240516508)

It's the best book out there for anybody wanting to learn more about film
processing and relating it to video post or digital intermediates.  Highly
recommended.


--Marc Wielage
  LA colorist-at-large








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