P3D Re: colour temperture (was tabletop question)

[CanterMike@xxxxxxx]

In digest 3298, Mark Dottle writes, in part:

<<  What
 color temperature is halogen lighting? (I don't want to use flash) I
 will probably shoot Sensia or Velvia film. Will halogen lighting produce
 a green or orange cast using these films? Thanks. >>

Photographic quality halogen lamps will produce 3200K .  Lamps can (and do) 
vary somwhat, however, and the "work lamps" you indicate may not be exactly 
3200K.  If the lamps (the actual bulbs) have an ANSI code stamped on them you 
can determine the temperture exactly.  The ANSI code is usually three letters 
(FHM or DXW or something similar, like projector lamps) but occasionally odd 
ones creep in (like Q750/CL [this is more common in stage/studio lighting 
than in projection]).  Note that (depending on your standards) you may want 
to determine the colour temperture of the lamps in the projector (since you 
plan to use it as part of your overall lighting scheme).

Sensia & Velvia are daylight (5500K) balanced films and both will show a 
colour shift when using anything other than a daylight source.  To use 3200K 
lamps witha daylight film you would need a blue correction filter, either one 
of optical quality in front of the lens or a "gel" in front of the light 
fixtures (the colour and transmission curves would be the same but the 
substrate differs).

Another option would be to use a film that matches the light source.  
So-called "tungsten" films are built to respond correctly to the 3200K lamps 
(but if you use them with a daylight source you will be back to needing 
filtration).  Fuji makes a very popular film (RPT, ISO index 64) and Kodak 
makes four (at speeds from 64 to 320).

I hope this helps.

Mike C


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