Re: Enlarger lens options.

Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
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.

I made a comparison between some better enlarging lenses for 24x36mm
(Apo-Rodagon 2.8/50, Componon-S 2.8/50, Focotar 4.5/50, Focotar 2.8/40
and Rodagon 4/60) and compared them at about 8x enlargement (20x30cm
paper size). Each was perfectly adjusted using a Peak #1, a glass carrier
and all enlarger planes were adjusted parallel using a laser tool. All
lenses were closed 2 stops from wide open.

The result: The only one you could distinguish from the others was the old
Focotar 4.5/50. It had a little curvature of field visible at the extreme
edges. That's all... no visible difference for the other lenses.

You can see the differences between the lenses with the Peak #1. The curvature
of field is readily visible for the two Focotars. The two Rodagon
and the Componon-S were much better and nearly identical. The Apo-Rodagon was
a little better wide open than the others, but all 2.8 lenses were unuseable
with this opening (for my view of quality...). Stopped down, all
were excellent.

Martin
.

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