"Lew" wrote in message
...
I replacing a Zone VI VC enlarger & head which after some
years of
reliable service seems to be becoming finicky. I'm fairly
certain the
electronics are not repairable, not to mention the prospect
of
replacing bulbs when that time comes ... or even evaluating
if that
time has come already. In any event, I have many years of
negatives
developed to a contrast level suitable for a cold light
head. This
creates the possibility that negs which I've printed on
harder paper
in the past will not print well in the contrast ranges
afforded by my
new enlarger with condensers. The simplest solution I could
think of
was to scale back my development times for new work, but to
get a cold
light head so as not to lose any flexibility printing my
older stuff.

Since it seems likely that this thread may go on to ask how
I chose
the Omega, I'll answer now: It has no more electronics than
a common
lamp and the bulbs aren't much harder to find either. I
can't envision
a time when this enlarger would become unusable.

For the most part I have had no difficulty in printing
the same negatives on either type of head. While variable
contrast paper does not _exactly_ duplicate the curves of
graded paper it comes close enough and can be adjusted over
a very wide range.
The difference in contrast depends on the design of the
head. Most condenser heads are partially diffusing because
the source is usually a large lamp with a highly diffusing
(opal glass) surface. This has the effect of lowering the
Callier factor and also makes focus of the condenser system
less critical. Ideally, the condensers should focus the
light on the entrance pupil of the enlarging lens. Probably
the best way to check for focus and alignment is to focus
the enlarging lens with a negative in the holder, then
remove the negative and examine the uniformity of the
illumination on the baseboard. The enlarging lens should be
stopped down enough to eliminate mechanical vignetting from
the lens mount, usually two stops is enough. The condenser
focus can then be varied to get the best center to corner
uniformity. The D5v allows continuous focus so its not hard
to find the right setting. Any lack of symmetry in the
illumination indicates that the optical system is out of
alignment. On Omega enlargers alignment is fairly
straightforward. I found on mine that once set it stays in
alignment pretty well. I bought mine used and suspect it had
never been adjusted since leaving the factory.
Beside the problems with variable contrast paper I
found that the cold light did not deliver enough intensity
for 35mm negatives. While the brightness of the diffuser is
constant one is using much greater magnification for small
negatives so the baseboard intensity can become quite dim.
Between that and the loss due to the density of the
anti-light-piping pigment in 35mm B&W negative support, the
exposure times for large prints were quite long. Since the
condenser concentrates the light at the lens this is
alleviated although the magnification still reduces the
illumination.
This is more than I intended to write. Try printing on
VC paper and experiment with the paper grades, I am pretty
sure you will be able to get satisfactory prints.


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Richard Knoppow
Los Angeles, CA, USA