[pure-silver] Re: Modified Agfa 108 with multigrade paper
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: "Pure-Silver Free" <pure-silver@xxxxxxxxxxxxx>
- Date: Fri, 16 Mar 2007 15:31:02 -0700
----- Original Message -----
From: "Georges Giralt" <georges.giralt@xxxxxxx>
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Friday, March 16, 2007 10:30 AM
Subject: [pure-silver] Re: Modified Agfa 108 with multigrade
paper
Hi !
Switching to a 4x5 setting for the condenser may be a
false good idea.
As the condenser set is an optic system, it has to be
somewhat matched to the lens used to project the negative
as Richard has pointed out previously. This may explain
why you've worsened the problem by placing your frosted
Mylar between the two condenser lenses. Give a try at the
solution I spoke about : place the Mylar above the
condenser set or below the set, just above the neg
carrier. (I prefer the first solution)
But, as Marc said, it could be a whole bunch of unrelated
problems working you nuts.
Oh, BTW, try another batch of printing paper, who knows,
your's could be bad...
I do not have a Besler enlarger so I am not that
familiar with the details of its lamphouse. However, it seem
to me that the condenser adjustment is continuous rather
than in steps as in my Omega D2V. The best uniformity will
be when the condenser is focused on the entrance pupil of
the lens. This, of course, varies with the distance the lens
is focused at. The size settings on a condenser are usually
approximations to the distance needed for lenses of the
focal lengths common for that size and for the magnifiations
commonly used, they may not be optimum even when using the
right FL lens and magnification. The 4x5 setting for the
condenser will focus the lamp at whatever distance the
manufacturer thinks a lens of approximately 150mm will be
when making approximately 11x14 prints or whatever. The
reason enlargers like the Omega can get away with this is
that the lamphouse is not a pure condenser, or rather not a
point light system. It is in fact mostly a diffusing system
with the diffusion coming from the "opal" diffusion surface
of the enlarging lamp. One is focusing the image of this
large, diffuse surface, rather than a point at the lens so
there can be quite a bit of defocusing before the mismatch
becomes evident in the form of uneven illumination. This is
also the reason that an "opal" lamp, like a PH-211 or 212
_must_ be used rather than an ordinary household lamp. Also,
anything on the top surface of the lamp will be focused on
the lens so it will show up as dark areas in the
illumination. Enlarger lamps have their trade marks on the
side rather than the top of the lamp for this reason. Dirt
on the lamp will also cause a similar problem.
Someone suggested aligning the enlarger, I think this is
a very good idea and wish I had made the suggestion. I have
had to align my Omega a couple of times although once
aligned it holds the adjustments well. Small variations in
parallelism can cause very large problems in both
illumination and focus. Most enlargers have some means for
making the adjustments.
I have also had problems with uneven illumination when
using very high contrast paper grades, but not at the
reasonably low value of Grade-4. When using the maximum
contrast filters, especially the late, lamented Agfa papers,
it was necessary to clean and check everything to get rid of
the blotches etc. These very high contrast grades will show
up the slightest scratches or even dust on the condensers.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
