> I'm trying a new enlarging lens (Nikkor 50mm f/2.8N) which has amazing
> resolution, but for
> some or other reason I'm getting weird light falloff, not in the
> corners as such, but
> in parallel to the long edges of my prints. This image shows it clearly:
I've seen this twice before. One was because the enlarger head didn't
have even lighting--this can get tricky, and the other time was when I
tried going too low on the enlarger to make a tiny print and a inverse
vignetting resulted.
I primarily use a diffusion head on my enlarger, but also have
columinated heads too. The inverse vignetting occured not with the
diffusion head.
Hmm. Something that MIGHT be happening. Remove the light head of the
enlarger and look straight down through it with your typical film
holder in place. Is the film holder bright reflective? If so, there is
backscatter which ends up causing an uneven lighting as this reflected
light bounces back up into the head which then comes back down in a
pattern that could result in wave shaped illumination. Remove the
holder and look further down. Is there anything bright reflective
inside the bellows are on the lens-board? If the lens board is
reflective, the light bounces back to the film and underside of the
holder. Usually, though, this type of reflectance below the film just
results in lost contrast. These issues with reflections inside the
enlarger are more likely when using small-format films inside a
large-format enlarger.
AG
--
_________________________________________________________________
Options: http://lists.thomasclausen.net/mailman/listinfo/olympus
Archives: http://lists.thomasclausen.net/mailman/private/olympus/
Themed Olympus Photo Exhibition: http://www.tope.nl/
|