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- Path: sparky!uunet!gatech!usenet.ins.cwru.edu!cleveland.Freenet.Edu!bu890
- From: bu890@cleveland.Freenet.Edu (Brian Segal)
- Newsgroups: rec.photo
- Subject: Re: 81A, 81B, & 82A filters: What are they for?
- Date: 1 Jan 1993 13:53:25 GMT
- Organization: Case Western Reserve University, Cleveland, Ohio (USA)
- Lines: 40
- Message-ID: <1i1iclINNoiv@usenet.INS.CWRU.Edu>
- NNTP-Posting-Host: hela.ins.cwru.edu
-
-
- The 80 series filters are Color Temperature Conversion or CTC filters.
- Their purpose is to change the apparent color temperature of the light
- received by the film in order to compensate for actual
- light conditions and match the existing light temperature to the
- correct recording range of the film. Daylight film is
- formulated to give a "true" color rendition when the color temperature
- of the light is about 5500 Kelvins. Any deviation will show up
- as either bluer or redder depending on the color temperature..the lower
- the light temperature the more the light shift to the red end of
- the spectrum and vice versa. This is all based on a theorhetical
- black body radiating changing colors as heated.
-
- You don't really need an expensive color temperature meter for most
- practical applications..a Kodak Professional Film Guide - which is about
- 20 bucks - will suffice in most situations...just consult the
- handy dandy dial...in fact I believe that even the tiny pocket edition
- of the film guide has the CTC filter dial.
-
- Here is the nomenclature:
-
- All filters numbered 81 and going from 81 to 81EF are warming filters.
-
- All filters bumbered 82 to 82C are cooloin filters.
-
- The above filters are for incremental graduated changes in color temperature
- with any film...obviously they have different functions with daylight VS
- tungsten films.
-
- The really powerful ones..the 80 series to convert daylight film to
- tungsten range and the 85 series to use tungsten to daylight are generally
- used primarily as film conversion filters..although in the extreme ends of
- the spectrum are also used for light balancing purpoises.
-
- Tungsten photo lamps radiate at about 3200Kelvins.
-
- All of this is in your Photo Guide...every one who shoots at all seriously
- should own a copy.
-
- brian
-