"A R" <news*NOSPAM*@[EMAIL PROTECTED]
> wrote in
message
news:1ifcdoj.2mqs62hnrnbdN%news*NOSPAM*@[EMAIL PROTECTED]
> I've started taking 6x6 photos. Instead of buying a new
> enlarger, I'm
> adapting my trustworthy MPP condenser to take 6x6 negs.
> This has
> involved fabricating a new lens board, fabricating a new
> neg holder,
> purchasing a new enlarging lens and replacing the
> condenser.
>
> Now, I have a pair of spherical condenser lenses but
> unfortunately I
> have no cell to mount them in. A single lens on its own
> fits snuggly in
> the enlarger head and seems (by eyeball) to give a uniform
> illumination
> across the easel.
>
> I know some enlargers use single apsherical lenses but
> what
> advantage/disadvantage do I have using a single spherical
> lens?
>
> Come to think of it, I'm not to sure why condenser lenses
> come in pairs!
>
>
> --
>
> I need more time!
Symmetry corrects coma, lateral color, and geometric
distortion. The improved coma and distortion probably
results in better uniformity of illumimation and lateral
color will reduce color fringing from the condenser system.
The symmetry does not correct spherical aberration but the
plano-convex shape of the condenser reduces it. Actually,
the spherical of the two halves of a symmetrical lens add.
Some enlargers use only a single condenser but, since
most condenser enlargers also use light sourses of
relatively large area and diffuse surface the aberrations of
the condenser have less effect.
Ideally the condenser should focus the source on the
entrance pupil of the enlarging lens but the focus is not
too critical where a large lamp with a diffuse surface is
used.
--
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@[EMAIL PROTECTED]
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