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

Re: Green Light



Charles Poynton wrote:- 

- The light source needs to have power in some spectral region where
   each dye absorbs.

Sorry if my phrasing was rather too wooly Mr Poynton, but that's what I was
trying to say.

But how could this be achieved with a flying spot TK? Cintel's system seems a
good compromise - the specs for the URSA do show a reduced s/n ratio in red
and blue channels but it's 3db at most (not insignificant, I grant you) but,
arguably, a price worth paying for scan effects/shuttle/active stop etc.

I don't see any way to match the absorbtion bands of the individual dye layers
without using specifically designed dichroic filtration and multi pass
scanning. It might become rather unwieldy if you proposed to scan more than
one type of emulsionin this way. Perhaps if you were to make monochrome
separations in camera at the outset you could bypass the whole dye issue.

As to what the colour looks like, it IS striking when you first see a flying
spot TK that the light source is green, and easy to leap from that initial
thought to - 'well, if the source is green, how the hell can the TK 'see' the
full range of colours?' Just as the first time you see negative, you wonder
why it's orange.

I'm not going to pretend that I know very much about this, but it's easy to
apply 'common sense' and come to the wrong conclusions. I have no idea, for
instance, what the unfiltered responses of either the Spirit's CCD or Cintel's
PMT's are, and surely (there's that word again...) these are as much at issue?
My basic argument is that both systems are a lot more complex than the
dominant colour of their light sources.

sincerely

Adrian Thomas
London,UK

---
Thanks to Complete Post L.A. for supporting the TIG in 1998..
No product marketing allowed on the main TIG.  Contact rob at alegria.com
957 subscribers in 36 countries on Mon Mar 16 19:37:09 PST 1998 
complete information on the TIG website http://www.alegria.com/tig3/