Lincoln Michaud wrote in message ...
>In article <19971212043801.XAA24502@ladder02.news.aol.com>, asisha@aol.com
>(Asisha) wrote:


>> Slide and negative film work different. You can increase contrast in some
>> brands of slides by underexposing them. Slide films have a narrow latitude so
>> you have to be very carefull when under/over exposing. Negative film does not
>> like to be underexpose even though has a wider latitude than slide film.
>> Always overexpose negative film, never underexpose it (if you overexpose the
>> lab will have something to work with). If you underexpose slightly your slides
>> will probably increase contrast. If you underexpose negative film you
>> will end
>> up with muddy, dark prints. On the other hand slides do not like to be
>> overexposed, and some photographers recommend to overexpose your negative film
>> 1 stop for better pictures.

[...]
>What should I set the ISO on my camera to achieve a 1/3 under exposure on
>my selection of slide film?
>
>For instance: should I set the ISO for Fuji Velvia at 53 instead of 50?
>Should I set the ISO for Kodachrome 64 at 68 instead of 64?


The advice above is good - and slide films, IMHO, are best exposed correctly!
;-), ;-) This means first establishing whether or not your camera is correctly
calibrated, and then whether or not a particular film speed rating is correctly
calibrated... In my experience, most slide films are correctly rated by their
manufacturers, though there are exceptions (Velvia is closer to 40, and the
Fuji and Kodak 400-speed films are closer to 320...). Try a short roll of
Kodachrome 64 rated at 64 and shoot it under a variety of conditions. If the
results generally look correctly exposed (try holding them up to a window with
a cloudy sky behind the slides to see if they look "normal" - neither too dark,
nor too light...). If a little too dark, try 50 for the next roll - if a little
too light, try 80 (the 1/3-stop sequence is 20, 25, 32, 40, 50, 64, 80, 100,
etc.). If quite a bit too dark, try 40 - if quite a bit too light, try 100...
When you get this right, apply the same amount of shift (in stops) to all other
films (this calibrates the camera metering and exposure) before applying
intentional shifts away from "normal'... (like an intentional 1/3rd stop
underexposure of slide film [I don't recommend it! ;-], or a 2/3rd stop
overexposure of negatve color film [I do recommend it, especially when shooting
under tungsten or flourescent light! ;-]).
Hope This Helps
David Ruether - http://www.fcinet.com/ruether