"otzi" wrote in message
u...
Thanks for all the input folks. I was curious but
unconvinced. Just wondered why so much was invested for so
little gain. But these responses were very encouraging.
Thanks.

Lots of snipping here.
There are a number of reasons for the newer lenses. One
is simply that lenses have a very long lifetime so buying
one often takes the buyer out of the market for some time
unless a "better" replacement can be offered. Another is
that computer aided design makes it easier to make new
designs and evaluate them. Before computers the lens design
procedure could progress only so far through mathematical
analysis at which point a sample lens had to built and
evaluated on the optical bench. The computer allows very
complex analysis to be made quickly so that new designs can
be brought much closer to optimum before one is made. Often
the difference between a computer optimized lens and one
designed by the older methods is slight. I also mentioned in
an earlier response to this thread that the optical glass
types available had changed necessitating redesign of many
existing lenses. Since many of these were designed before
computer optimization became generally available the
redisign for new glass types also resulted in either
improvement in the original design or a completely new
design.
Nearly all modern enlarging lenses are based on a
generic type known as a Plasmat as are many large format
camera lenses. These have several inherent advantages such
as low astigmatism which is important for flat field
applications such as enlarging. They are also have
relatively wide coverage angles.
Modern multi-coating also helps performance by
increasing the image contrast.
Keep in mind that any lens with fixed position elements
can be optimized for only one object to image distance. The
performance at other distances can be good but will not be
quite up to the optimum distance. Most camera lenses are
optimized for approximately infinity but enlarger lenses are
optimized for whatever distance corresponds to the
magnification the manufacturer thinks it will be used for
mostly. Some manufacturers, Rodenstock and Schneieder
particularly, specify the magnification range for their
lenses. While the lens can give satisfactory performance
outside of this range special range lenses will do better.
Both manuacturers offer lenses for relatively large
magnification, i.e., photomurals, as well as for more usual
size prints. Since the print size does not vary so much with
differences in format (one makes 8x10 or 11x14 from all
common negative sizes) the optimum magnification will vary
with the lens focal length, that is, it will be greater for
a lens for 35mm than for a 4x5 lens.
A high power grain focuser will often show up
differences in lenses that are much harder to see in a print
but may also introduce its own problems, for instance, some
grain focusers are not very well achromitized and will show
color fringes due to its own optics which are not present in
the image from the enlarging lens.


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Richard Knoppow
Los Angeles, CA, USA