Re: [Leica] Exposing Tri-X at 320

["Dan Post" <dpost@triad.rr.com>]

Dan(2)
HO-BOY! You're in my area of incompetence now!!!
Tell them to develop normally, the lattitude of the fil will take care of
itself, especially if they are printed on VC paper.
Years ago, the ASA was listed on a little paper sheet- we always called them
'dope' sheets as they had the latest 'dope' on the film, and if you were too
dopey to remember the details explained, it was a good idea to keep it
handy.
They used to say that the film speed, or exposure index they recommended was
the MINIMUM for a usable negative with sufficient detail in the shadows.
Now, I know they have changed the so called 'speed point' of their films so
that the recommended exposure is a little more conservative.
Now- if you consider that a good shadow detail has a density of .10 to .20
over base+fog, then a third of a stop over exposure will usually keep that
shadow density inside the recommended limits.
For example, if they develope film exposed at EI 400 and get a shadow detail
density of .10-.12, and they develop with a contrast index of .50, say, then
for every stopof illumination, or .30 change of light, then a change in
negative density would be a corresponding .15!
So, if you gave the film an over exposure of 1/3 of a stop- of a log
increase of .10, the corresponding change in the negative density in the
shadow would be in a ranng of about .05.
This means that with an EI of 400, and the film developed to a contrast
index of .50 or thereabouts, and a shadow detail would normally be, say
.10-.12, then overexposing by a third of a stop would mean the resulting
shadow detail would be in the neoghborhood of .15-.17, and still within the
'normal' shadow detail density of .10 to .20 about base+fog!
So you can see the lattitude of the film can take care of a lot of variation
of exposure, particularly overexposure. I have overexposed Tri-x a full stop
and shot it at EI200, developed it normall, and still got nice printable
negatives from it!
Don't sweat it! Shoot away- at EI 320 or even 250, and you won't be
disappointed!
Dan ( densitometer in hand!) Post
- ----- Original Message -----
From: "Dan Honemann" <ddh@home.com>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Tuesday, July 25, 2000 5:04 AM
Subject: [Leica] Exposing Tri-X at 320


> If you intentionally overexpose by a third of a stop by rating Tri-X at
320,
> do you then under develop by the proportionate amount?  Or do you develop
as
> normal and let the latitude of the film compensate for the overexposure
> (hoping to bring out more details in shadows)?
>
> I ask because I've never tried this before, and having shot a few rolls
this
> way, am about to take them to the lab to be processed and wonder if I
should
> say anything.
>
> Thanks,
> Dan
>
> P.S. All six rolls were shot with a Leica M6 (vain attempt to keep this
OT).
>