[rollei_list] Re: Macro with Enlarging Lenses on the SL66?
- From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
- To: <rollei_list@xxxxxxxxxxxxx>
- Date: Sat, 9 Sep 2006 07:25:13 -0700
----- Original Message -----
From: "Mike Kovacs" <mskovacs@xxxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Saturday, September 09, 2006 5:11 AM
Subject: [rollei_list] Macro with Enlarging Lenses on the
SL66?
Has anyone fooled around with enlarging lenses for medium
format macro? I recently picked-up 50mm and 80mm 6-element
Nikkor enlarging lenses and I wonder whether its worth the
trouble to adapt them to my Rolleiflex SL66?
Do they cover 6x6? If so, any idea of which f/stop and
amount of extension required for coverage? I'm just trying
to get a ballpark number to see if they fall into a useful
magnification range for me.
I wonder how sharp they will be? The 80/2.8 Planar seems
to perform pretty well but I think the 50/4 Distagon
suffers in the macro range from being a retrofocus design.
I don't own one but the 120/5.6 S-Planar is just too long
to consider for some of the higher magnification work I
do.
I haven't got the enlarging lenses yet (still in the
mail). I assume they are LTM in which case I can rig up
something to mount them. A blank SL66 lens board from
Hadley Chamberlain and a junked Soviet LTM lens mount
ought to do the trick.
Any guidance somebody can provide that has been down this
road?
---
FWIW, I've used enlarging lenses, specifically Schneider
Componons, as macro and micro lenses for LF. My
understanding of the definition is that macro photography is
very close but where the image is smaller than the object,
micro photography is where the image is larger than the
object. For micro work the lens must be reversed to obtain
best correction.
The 80mm should cover 6x6cm at any object distance but
will be best where the object is at the same distance as
used in enlarging. 6x6 enlarging lenses are usually
corrected for about a 1:5 magnification ratio. The 50mm lens
will cover where its used rather closer. Any lens will cover
double its infinity coveage at 1:1, however, enlarging
lenses for 35mm are generally corrected for a magnification
of around 1:10 to 1:15 so it won't do for table top or
similar work.
For micro work the conjugates are reversed. The side of
the lens which in enlarging faces the film is here oriented
toward the object. The optimum distances (and magnification)
is still the same but the other way. So, for instance, a
reversed 50mm lens works fine for enlarging coin sized
objects to an 8x10 negative. The object field covered will
be about the same size as the negative the lens is designed
to enlarge and the image size will be similar to the print
size, although, of course, smaller film can be used for
greater magnification.
It is a principal of optics that a lens with fixed
position elements can be simultaneously corrected for
spherical aberration and coma for only one object distance.
Depending on the lens the correction may remain good over a
wide range of distances, or may become significantly
degraded much beyond the optimum point. As a rough rule of
thumb the stability of the correction is better as the
curvature of the elements becomes less, so, slow, rather
narrow coverage lenses tend to have more stable corrections
than fast or wide angle lenses. Hence a process lens, like
the Goerz Apochromatic Artar, which is optimized for equal
object and image distances, can work very well even at
infinity focus if stopped down a little, where very fast
lenses, for instance a Zeiss f/1/5 Sonnar or Schneider
Super-Angulon, is not suitable at fairly close distances, as
in enlarging, unless stopped down considerably.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
---
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