[pure-silver] Re: donuts on prints
- From: Laurence Cuffe <cuffe@xxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 09 May 2007 08:52:17 -0700
I think it would be worth opening up the lens a bit more and seeing if the
donuts remain. Ideally the wider the aperture, the more resolution is
achievable in the final image. This applies to both enlarger and camera
lenses. Stopping down increases the depth of field, but can bring into focus
all sorts of details of the optical system which you normally don't want to
see, as well as allowing diffraction effects to come into play. Additionally,
it will allow random light leaks from the enlarger which would normally be
swamped by the direct printing light to com to the fore, and dominate the
image. This may lead to a loss of contrast for diffuse leaks and ghost images
where the light is more localized.
While the idea that your donut results from reflected light coming back off the
front of your printing paper is appealing, I'm having difficulty envisaging a
light path back into the system which would give rise to the effects you see,
where the donut appears to be focused. You might like to check this on the
original print.
You might also want to check how the lens barrel is fitted into the enlarger,
as a light leak through a narrow gap around the perimeter of the lens could
give rise to something like this. I think turning the enlarger on with the lens
stopped down and raked out and then examining it from beneath using either your
head , or if it thats awkward, a small mirror, might go a long way towards
resolving the problem.
All the best
Larry Cuffe
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