Pressure or Processing?

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dan.c.quinn@att.net - 21 Oct 2005 23:22 GMT

I shot a zone three through seven gray sheet
series with my RB67 Pro S for test purposes.

I noticed that the negatives had noticable
transverse density variation. The grey sheet
is OK. Uneven development first popped into mind.
Then it occured to me that the cause might be due
to pressure affects. I often advance to the next
frame using two or three partial moves of the
film advance lever.

Could my film holder have too much of a grip?
Could there be anything to it; pressure marks
due to to film advance? Dan

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John - 22 Oct 2005 05:52 GMT

> I shot a zone three through seven gray sheet
> series with my RB67 Pro S for test purposes.
[quoted text clipped - 10 lines]
> Could there be anything to it; pressure marks
> due to to film advance? Dan

I haven't seen such a problem with my RB67SD. Which films are you
using ? Is there any regularity to the variations ?

John

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Nicholas O. Lindan - 22 Oct 2005 15:19 GMT

> > I shot a zone three through seven gray sheet
> > series with my RB67 Pro S for test purposes.
> >
> > I noticed that the negatives had noticable
> > transverse density variation. The grey sheet
> > is OK.

The lighting is uneven. Meter it with an incident
meter.

For this test I would recommend open shade or
heavy overcast. Hard to beat the sky for a
diffuse source.

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Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
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dan.c.quinn@att.net - 23 Oct 2005 22:57 GMT

> Is there any regularity to the variations ?

Enough to suspect a pressure problem. The 20 X 30
inch Sturdy Board is Very uniformly grey coated one
side. I always expose a series at a time of uniform
sky lighting. Only takes about five minutes.
I like the zone three through seven series because
it contains the zones which print and can be easily
done at same stop OR at same shutter speed.
I'll finish a series today if the light holds
steady. Delta 3200 is loaded rather than the Pan F+
refered to in my first post. I did notice yesterday
while shooting frame one quite a lot of resistance
when advancing to frame two.
The film holder has two screws, film and take-up,
which may adjust film advance resistance. Dan

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David Nebenzahl - 22 Oct 2005 20:37 GMT

On 10/21/2005 3:22 PM dan.c.quinn@att.net spake thus:

Doubtful. If there was enough pressure to have any kind of effect on the film,
there would be some kind of physical damage to the film, at least to the
emulsion. Since you reported none, your problem seems to be uneven illumination.

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dan.c.quinn@att.net - 28 Oct 2005 11:28 GMT

Too vigorous and too much agitation of the Pan F+
are likely the cause of the transverse density variation.
The out of date by three years Delta 3200 I processed in
a carbonated non-restrained developer was well fogged
but very even in density. I made zone 3, 5, and 7
gray board exposures. Dan

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