Re: [Leica] B&W film speed

[Bill Welch <welch@pressroom.com>]

At 07:20 AM 2/21/99 -0800, you wrote:
>To LUGers with darkrooms:
>
>Recently Nathan Wajsman listed the ISO/EI speeds he uses to expose various
>B&W emulsions (Delta 100 at EI=80, etc.). The impression I get from his post
>and from other posts on the topic of film speed is that he and others of you
>with darkrooms generally shoot a given B&W film at the SAME ISO/EI speed
>irrespective of lighting conditions. Is that true? If so, WHY? 

No, of course not. You rate the film at the speed you need to deliver the
image. Only someone who doesn't really NEED the image would contend they
couldn't adjust development and EI as needed.


>Those of us using commercial labs may not have the option of varying
>development times, but I assume those of you with darkrooms DO change BOTH
>exposure times and development times to control contrast. For example, for
>PAN films in high contrasting situations (rodeo riders in bright sun at high
>noon), I would be inclined to over expose (effectively increase the film's
>ISO) to preserve shadow detail and under develop in the darkroom to control
>high lights. That way, I would be likely to get a smoother, more printable
>negative to work with.


It is an advantage on many levels to develop your own negatives. You can
get them the way you like, to make printing easier. That can make a
tremendous difference. The negative is the thing. But if you work with your
lab, and they are any good, they should do push processing and development
to your specifications. 


>So, if I have access to a darkroom and I'm in control of the films
>development process, I don't just assign one ISO/EI number to an emulsion. I
>may have a base number I start from under "normal" lighting conditions, but
>I vary that number according to the specific lighting conditions I face when
>I shoot a roll and the specific sort of results I want with respect to
>contrast range on the negative. Am I making sense here? Is that how you
>folks with darkrooms work or do you stick with one film speed for each
>emulsion?


Of course. Look, if I'm shooting in changing lighting conditions, I might
come away with several rolls of the same film at different speeds. Say
you're shooting sports outdoors under lights. You may start with a lot of
ambient, by halftime have little, and by third quarter have none but the
field lights. Some fields are well lit. Some are not. If your action is
moving, you won't not want your shutters speed to fall below 1/500, or
maybe 1/350 or 1/250,  and you are shooting wide open at f/2.8. You have no
choice but to push the film or pack up and go home. Reminders that you'll
lose shadow detail above 1000 or something are just a joke. The idea is to
get the image. Photographers deal with this ever day. They make the film do
what they need, if that means pushed one, two, three stops or whatever. B/w
or color.
Bill