The most common
faults that crop up
in the course of processing a film.
Spots
on the negative indicate
two things: there was dust on the film at the time of exposure
and/or fairly large round spots on the negative indicate that air
bubbles were trapped against the film during the process and
suggests insufficient agitation. This can be avoided by agitating
for thirty seconds at the beginning of development and by tapping
the tank on the bench. (some developers require longer agitation).
It must be stressed that too vigious and lengthy agitation can
induce the same problem. A way of helping to reduce air bubbles is
to use a pre-soak. Some developers like PMK Pyro and Rollie's R3
require a pre soak as standard.
Black
crescent-shaped kinks and clear patches more
common with roll film but can happen with 35 mm cassettes, this
happens where the film has been forced into the spiral making the
film kink and touching the film beside it.
Lines
are most commonly
caused by the film running across a small piece of grit on the
cassette opening. It can also happen by over tightening the film in
the cassette and bad handling. One of the most common, which has
happened to me, is the use of a squeegee to dry the film. I have
not used one since.
Finger
marks on negatives
are caused by handling the film with wet, dirty and contaminated
fingers. This can be eliminated by using disposable gloves during
the wet process and cloth cloves when handling dry negatives.
White
marks are caused
by grease and fixer before development and dark marks by fingers
covered in water or developer. Slight damage can be retouched.
Reversal
of negative image is
due in part or total to solarization making the negative into a
positive; this happens when light gets to the unprocessed film
during development. Care must be taken with the processing tank
that the lid is fully secure before inverting.
Uneven
image density is a
sign that there is not enough developer in the tank or lack of
agitation. A low-level of developer in the tank will show as a dark
unprocessed line along the top edge of the film.
Reticulation
is a lot of fine cracks in the emulsion this is caused by washing
in too high a temperature or solutions greatly different in
temperature. This can be avoided by making sure that the solutions
only have a few degrees difference between them.
Deposits
on the negative and discolouration.
Hard water may cause a chalky deposit on the negative that cannot
be washed away in water. It can be treated with a two percent
solution of acetic acid, then washed in clean water. The same sort
of problem may be due to the fix losing its acidity. A treatment
would be to harden the negative in one percent solution of
formalin, then wash in sodium carbonate followed by water.
Yellow-white negatives may be due to deposits of sulphur from a
decomposing fixer, it can be remedied by hardening in a one percent
formalin solution and washing in a ten percent sulphite solution at
thirty-eight degrees.
This is
the rule on tilting the easel and carries on from my last post. The most accurate way of correcting distortion
is to use Scheimpflug's principle: This states that you should tilt the
negative as well as the baseboard and that they need to be canted over in
opposite directions to each other. Additionally the incline should be such that
the plane of the negative and the plane of the baseboard should meet in the
plane of the aperture to give maximum sharpness over the whole image.