[photo-3d] lenses for twinned SLRs

["Jim Harp" <matmail2@xxxxxxxxxxxxx>]

Gary Schacker and I have been discussing our twinned Ricoh XR-10Ms SLRs off list - with his permission I'm posting some excerpts.

Gary:  I finished off the rolls that I removed from the cameras to do the twinning and got them back today.  Everything's working fine.  These frames were shot with one camera behind the other and I notice no fusion problems at all...Do you have a good selection of lenses?  I've got 28mm, 40mm, 50mm and 135mm
sets, all with 49mm filter threads.  What kind of bar do you have them on?

Jim:  I'm curious how you choose between the 40mm and 50mm lenses when shooting.  Is there another difference between the two lenses?  I currently only have 28 mm and 50mm.   I've been thinking of getting a 28-80mm zoom lens and just using the outer ranges to keep the image size consistent.  I find this idea appealing, as it would save me having to change lenses for most of the shooting I do. Also I'd like to see if slight fiddling with the zoom could compensate for size disparity in "one behind the other" close-ups.  Currently I'm using Dalia's 9 inch twin bar, and I also carry a pair of cheap lightweight tripods in my bag for hypers.  This is why I was so interested in being able to connect
my remote release via the dual phone jack - these tripods are too flimsy for anything but remote release shooting.

Gary: I probably would not have set out to obtain both 40mm and 50mm lenses for the Ricohs but I had a selection of Pentax bodies and lenses long before I started using SLRs for stereo, so I picked up a mate for the 40mm lens I already owned.  The Pentax-M 40mm f2.8 lens may be the smallest and lightest weight SLR lens ever made.  It's sometimes called the "pancake" lens because it's so short and flat.  If compactness and lightness are important to you it's a neat lens to have. Unfortunately they're rather expensive on the used market, commonly priced at $200 each or so.  Anything less would be considered a good deal I guess.  I do find that there is enough difference between 40mm and 50mm that it's worth carrying both.  One drawback though, I do a lot of night shooting and these lenses are not suitable for that application.  They produce unacceptable internal reflections of pinpoint light sources

I've decided to use only prime lenses for stereo.  I find that variable aperture zoom lenses (all but the most expensive zooms) are problematic for precise exposure calculations, since you never know just what f-stop you're at.  I use a hand held meter or sunny 16 derived exposures.  Also I think zoom lens makers outright lie about the speed of their lenses.  I've used zooms
that at f5.6 are really more like f-11.  I just don't trust them.With primes f8=f8!  Also, you can't beat the image quality and bright viewing image of a prime lens.

I would really recommend picking up a pair of 135s.  Synchronized hyper stereos with telephoto lenses can be stunning. This type of shot won me "Best of Show" at the Chicago Lighthouse Exhibition this year.  Telephoto lenses will get you past the foreground that cannot be included in wide base
hypers.  Look for the Pentax M series 135mm f3.5 lenses.  All the "M" lenses were brought out in the 1980s to match the compact ME and MX series of cameras.  You should be able to pick them up for about $75 each.

I also use the small bar that Dalia sells, I've got several of them.  I find them just the right size for the beloved Ricohs and very sturdy.




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