Chuck Norcutt wrote:
> If used enlarger lenses are inexpensive it occurred to me that it might
> be useful to have a long focal length enlarger lens to add to the small
> stable of 50 and 90mm macros. I thought it might be useful as a copy
> lens for greater working distance.
>
There are some practical problems.
1. Bellows. These lenses don't have any focusing mechanism, so they need
to be bellows mounted. A normal 35mm style bellows won't work with the
long ones. The rear portion of a Schneider Componon 150/5.6 fits into an
OM mount on the bellows with about enough room to spare to allow an
adapter. A 240/5.6 and a Rodenstock Omegaron 210/4.5 are both WAY too
big to fit. At least a MF bellows would be required.
2. Mounting. No problem for someone with access to a machine shop. :-)
I don't know if the mounting threads for these lenses have some sort
of standards, but if so, they are not related to anything to do with
35mm format equipment. All that I've seen come with a mounting ring to
attach them to a lens board using a simple hole of the appropriate size.
> But then I wondered if any of these long lenses are really up to the
> task.
Yes, I believe they are. The long fl enlarging lenses I have are left
over from production of a series of rather large rear projection units
for viewing maps and aerial photos that I conceived of, helped design
and had built. They projected 4x5" transparencies onto 6x7 foot screens.
Using a rotating turret, and film holder that moved up and down in the
optical plane, ala the Beseler "Cone of Light", and orthogonally to the
optical axis to allow viewing any part at higher magnifications, all
automated, they projected at three different magnifications.
We used a custom built camera with another 240 mm Componon with shutter
to make the slides and used a special order Kodak film originally
created for high altitude photography, It was rumored it was developed
for the U2s. Whatever its provenance, it was astonishingly sharp and
grainless. Just a little tricky to process, which we also did ourselves.
A group from the Lawrence Livermore Lab came to visit once to find out
from my cartographer/photographer how to process it without the emulsion
sloughing off and going down the drain. :-)
Anyway, I don't remember now the maximum magnification, but it was
around 40x with a 105 mm lens. I could stand right up at the screen and
see no grain and lots of detail. The lowest magnification was still
about 17x, and very high quality.
> It has been rumored that some 35mm Canyon lenses are not up to
> the resolution demands required by the pixel density of the 5D and other
> full frame digitals.
AF general purpose taking lenses and top quality enlarging lenses are
almost unrelated. The optical requirements and resulting designs are
sooo different.
> Furthermore, MF lenses don't need to be designed with resolving power
> equivalent to 35mm lenses
We've been around this one before, with all sorts of theories propounded
and positions taken. The generally likely truth is that the optical
tradeoffs to maintain reasonably flat field and minimal aberrations over
the bigger image circle do almost certainly mean lower lppmm resolutions
in MF lenses, although probably not in proportion to the increased
negative size. Still, you are again talking about taking lenses, not
enlarging lenses
> so what's the chance that an MF enlarging lens will resolve 13MP on a 35mm
> size frame
I think it's pretty good, based on my experience..
> let alone the higher pixel density of smaller sensor cameras?
>
Who cares? ;-)
Moose
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