On Mon, 19 Dec 2005 14:07:19 +0100, Jostein <[EMAIL PROTECTED]> wrote:
I'm looking for something to achieve ca. 4x magnification.
I have a bellows with a total extension of 130mm. That gives roughly
2.5x with
a
50mm. A good 28mm lens would probably be optimal with a bellows, giving
4x at
112mm extension.
Or maybe the 31mm limited? The built-in lens hood is a PITA...
However, a bellows solution is a second best. I hope to find an
optically good
combination of two stacked lenses to give 4x. It is so much more
convenient in
the field to use open-aperture metering...:-)
So far I've tried FA 100/2.8 macro with FA* 24/2, and A*200/4 macro with
FA
50/1.4. The latter is a lot better than the former, but still not quite
there.
Stopping down the 50mm to f/2 improves contrast, but introduce more
optical
errors with small apertures on the 200. This leads me to believe that
the best
50mm would be the one that is the sharpest at full opening, whatever
that may
be...
Hi Jostein,
Not much worthwhile experience to relate, but:
Mr. Paul Harcourt Davies recommends lenses from 24 to 50mm stacked on
lenses from 100 to 200mm in his book 'close-up & macro photography'. He
claims the stacked lens should be used wide open, and the other lens
stopped down to 16, to make sure you use the center of the stacked lens.
That suggests a 'sharp wide open' 50mm lens won't help you much: you're
using the center of the lens already. Or am I confused on why lenses
improve when stopping down?
He claims zooms can theoretically be used, but that he didn't find a
suitable combination. I wasn't too unhappy with the results of a Zenith
58mm reversed on a FA 70-200: <see the last three at
http://www.jenny.dds.nl/lucas/macro/macro.htm>. These are flatbed scans
from 10x15 prints (*blush*), the pen-tip enlarged nicely.
He also suggests an enlarger lens could be use as stacked lens, maybe
that's worth looking into?
Hope this helps,
--
Regards, Lucas
