81A, 81B, & 82A filters: What are they for?

[rsm...@pearl.tufts.edu]

I've got three filters that I got years ago. They were originally lying around
with some unused equipment or something that my father found, so I don't know
what they're for. One is an 82A (light bluish-green color), the others are
81A and 81B (brownish-yellow). What are these things used for? Thanks for
any information.

[Ty Monson]

These filters are used for making small modifications to the color
temperature of lighting. The 82A shifts light to a higher color
temperature like an 80A filter, but not as much.
Similarly, the 81A and 81B shift to lower color temperatures, but to a lesser
extent than the more commonly used 85B filter.

I find that the 82A is useful to use with an 80A when photographing
under very yellow light sources, such as 60 and 100 watt incandescent
lamps. The 81A and 81B might be useful to correct for the bluish
appearance in a shady scene exposed to a clear blue sky.

Proper application of these kinds of filters requires use of an expensive
color temperature meter. But you can experiment to see what results
you can get.

For a better understanding of these filters, I recommend getting a book
that discusses photographic applications of filters. Titles may mention
filters expressly, or filters may just be a section of a book on
photography. Check the index for the word "mired". If you find an
explanation of the mired system, you will quickly see where your filters
fit in the over-all pattern.

[Vax BULLET-IN-Board SysOps]

In article <1992Dec31...@pearl.tufts.edu>, rsm...@pearl.tufts.edu writes...

I'm new to photography, so i've not been using many filters. but
i do use the 81A fairly often. Its used mainly to give warmer skin
tones when shooting under cloudy weather or when shooting with
flash guns which would normally cause a bluish tinge.

[Brian Segal]

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

[Robert Claeson]

If my memory serves me right, the 82A is used to adjust the color
temperature slightly towards a cooler image tone. The 81 series is for
adjusting towards a warmer tone with color films. The 81A is a very usable
filter. The 81B is stronger, and combined, they give a very pronounced
effect, similar to that of an 81E filter. Try the 81A filter for portraits.

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