Sunday, February 10, 2008

Close-ups with a Stereo Realist – Closer than 2.5 ft

The Realist can focus as close as 2.5ft. If you want to focus closer then you have to either fool around with the focusing wheel or attach close-up (supplementary) lenses.

The limit of 2.5 feet is imposed by the rotation of the focusing wheel, which is limited by a small screw. This screw can be removed (see picture) allowing the Realist to focus even closer. It has been reported that the “second round” of the focusing wheel corresponds to focusing distances from 20 inches (at INF) to 14 inches (at 2.5ft) but testing should be done to get the exact focusing distance. This testing can be done by using a ground glass and a magnifier and observing a test image.

If you decide to experiment with this method make sure you don’t lose track of which round the wheel is at. Also, because the focus plane is pressuring the film, you should turn focusing to infinity before advancing the film.

We discussed close-up lenses in previous postings. With a little imagination you can attach close up filters (or any filters) to your Stereo Realist camera. For example, I have used a film cap with a 20mm hole, with the filter attached to it, over the Realist lenses (see picture). Some people have used the Realist Film ID unit for macro pictures. This unit is essentially a strong close-up lens with the advantage that it attaches to the Realist lenses and offers a holder right at the near sharp focus distance. You must find some way to shift or rotate the subject for stereo relief and you need to move the unit from one lens to the other without disturbing the setup. Sounds like a challenge.

Here is a Table that summarizes key variables when using the +1 and +2 close up lenses with the Realist focused at 2.5 ft.. In-between magnifications can be achieved by focusing the camera further. For example if you use the +1 lens and focus the camera at 10ft, then the actual focus point is at 30 inches (2.5ft) which is the same as the near focus without lenses.

The drawback of these extreme close-up settings is realized when we look at the image loss. Using the +2 lens at 2.5ft focus we lose 8mm of image. This leaves us with 23.5mm – 8mm = 15.5mm of useable image width. There is no slide mount that can mask this (4p/Half Frame/Nimslo mounts have 16mm openings)

One way around this problem is to use prismatic close-up lenses. These have the shape of a wedge and must be aligned over the lenses. In addition to changing the focus, they also shift the image to reduce/eliminate image loss. The drawback is that they introduce aberrations and distortions.

I am familiar with the “Stereo Angle-Lens”, a prismatic close-up lens manufactured by Photo-Liz Inc in Long Beach NY. As seen from the copy of the instructions reproduced here, these filters come in 3 different strengths. Of interest is the “neutral” filter which is a simple prism. This is used to push the window back in close ups without filters or also to push the window forward when taking hyperstereos!

I have tried these filters for an extreme close-up portrait of my daughter. The results were interesting, but the resulting image has too much stretch and distortion for my taste, even when viewed in the viewer.

The bottom line is that for extreme close ups with the Stereo Realist, you need to reduce the stereo base. Some people have used the Realist and a slide bar for close ups. This procedure will reduce the stereo base in a stereo pair, without wasting any film: Cover the right lens, and take the first picture. Do not advance the film. Shift the camera slightly to the left (to reduce the spacing of the lenses). Cover the left lens and take the 2nd picture. I have seen a portrait taken with this method! (The model must stay still for along time). This method might have novelty value, but if you are going to use a slide bar, it is much more convenient to use an SLR camera, not the Stereo Realist.

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