Archived posting to the Leica Users Group, 1999/02/21

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Subject: Re: [Leica] B&W film speed
From: "Martin V. Howard" <>
Date: Sun, 21 Feb 1999 17:15:47 +0100

Gib Robinson wrote:
> 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? (As my

Exposure determines how much light the shadows get, so setting a film
to a particular EI exersizes control over how the shadows will be
rendered on film.

Development is then used to control where along the contrast curve the
highlights are placed.

Conseqently, the EI stays the same for varying lighting conditions, but
the development will differ (if you want to take that into effect).

Personally, I just use a ballpark system: I overexpose film by 1/3 to
1 full stop and then develop slightly less than manufacturers'
recommendations.  When I measure light, I use an incident meter and
keep the dome half-lit, half in shadow.  This gives me pretty a fast
and flexible working system.  If the scene is extremely contrastly, I
might pull the development a little early, but typically I just stick
with what I've previously determined and use multigrade paper to make
any compensations.


- -- 
Martin Howard, Grad. Schl. for Human-Machine Interaction,  |
HMI/IKP, Linkoping University, SE-581 83 Linkoping, Sweden.|    Just
Tel: +46 13 28 5741; Fax: +46 28 2579; ICQ: 354739         | say "DOOH"
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