Slide holding for Scanning - Ohnar and Other Options

Bernard Delley wrote:

very nice work with your DIY brass holder !

Sorry to be so late commenting about the lens.

There are several reasons why your old enlarger lens may produce less good results than other options.

- a basic minor issue is that the focal length of 80mm is a bit long, requiring quite a bit of bellows extension. This is slightly inconvenient. A focal length of 40-60mm would give a correspondingly shorter setup. In my dpreview tech album you can find several images from my explorations on camera slide digitizing: this or that .

- another issue may be with the sharpness of the enlarger lens. I stems from film time, when a circle of confusion of 1/30 mm was considered sharp enough for DoF considerations. Also the f/4 enlarger lenses were typically Gauss type designs with 4 lenses in two groups, while f/2.8 were produced as higher corrected designs with 6 lenses in 4 groups.

- and an 80mm enlarger lens may be designed for a magnification range of 3-8x or similar, while slide copying is at 1x or 1:1.6x for the APS-C crop camera.

I use the Olympus OM 80mm bellows macro lens, which is designed for use at 1:1. It can be set at 1:1 on a bellows with my Sigma camera, which has an SA mount. The flange to sensor distance is 44mm, the same as for EF.

But it will always be easier to set up a bellows on a mirrorless camera, because of the much shorter flange focal distance. It is also easier with FF than APS-C, because the larger image puts the lens further from the sensor.

- photographic close-up lenses are typically designed to cover magnification ratios up to 1:1. Older lenses can be quite good and come very cheap. Newer lenses may be better than really needed. Do not ignore that modern, internal focus, lenses should be mounted directly on the camera. They would be outside their design specifications when mounted with about 50mm extension on a bellows.

Don Cox