[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Rank Cintel phosphor cor

 Reply to:     RE>Rank Cintel phosphor correction 
This IS a hairy question. I will take a stab at it with the hopes that my
colleagues out there will jump in and help me when I am about to fall over the

The RANK flying spot scanner is in itself not tuned to a a specific colorimetry
in terms of SMPTE, NTSC or EBU phosphor sets. Typically, the scanner uses
matrices to tune the response of the scanner to accomodate the CRT and FILM DYE
characteristics. This is called MASKING. The masking is a matrixing operation
that is adjustable to accomodate various film stocks. It is necessary because
the spectral response of the CRT, when combined with the spectrally overlapping
dye response curve of film, causes "contamination" of the RGB photocell outputs.
The matrices are used to subtract out contaminating components and thus are
specific to each film type.

Having said all that, let's note that most people just ignore the masks
altogether and utilize their color correction panels (lots of knobs there) to
tweak out offending colors. But purists will recognize the value of correctly
applied masking.

In the end, the colorist is evaluating the picture on monitors which are almost
invariably have SMPTE phosphors and are set for SMPTE D65 (6500K) white balance.
Occasionally, the monitor will have an "NTSC MATRIX" to simulate the look of a
picture should it make its way to a monitor with NTSC phosphors, but in practice
this is rarely used.

Practical experience (guys, jump in if I am misinformed!) shows that the
phosphor sets used in most commercial receivers are close enough to the the
SMPTE primaries to not be a real concern. And, as far as I know, the earlier NTSC
phosphors are rarely found today. Those phosphors have been supplanted with more
efficient phosphors over the decades, and have drifeted away from the original
xy coords specified in the NTSC set.

There is a relatively recent (past 2 years?) review of phosphor development
which was published in the SMPTE journal. I don't have that issue close by, but
when I go home I will dig it up and pass the info on to you. The previous
paragraph is based on my hazy alcohol-zapped memory of that article.

I hope this helps some.

Bill Topazio / EDITEL NY / bt at edny.univid.com

Date: 09-05-94 11:22
To: Topazio, Bill
From: wlrc at uhura.neoucom.edu

I have an engineering question which turns out to be surprisingly
difficult to get an answer for.  I am turning to this mail list in
hopes that someone may know or may put me in touch with a
knowledgeable person.

Q. Are telecine transfer machines, e.g. the Rank Cintel, color
corrected for the original NTSC monitor phosphors or for the later
SMPTE C ones?

I am not a telecine professional but a writer for THE PERFECT
VISION.  We desperately need an answer to this question to aid in
our evaluation of consumer television monitors (since they use
neither of the above phosphors, they should include a correction
matrix, but for which one?).

Bill Cruce,    DAY: 216-325-2511 X321,   NIGHT:  216-673-1974
INTERNET: wlrc at uhura.neoucom.edu           FAX:  216-325-7943 
Neurobiology Dept, NE Ohio U Coll of Med, POB 95, Rootstown, OH 44272