Slide holding for Scanning - Ohnar and Other Options

Halina3000 wrote:

Thanks. i've been thinking about this some more but have reached a bit of an impasse. As far as I can see my test results show that a 50mm enlarger lens is not going to work with the BPM bellows. Without the bellows there is no way to focus.

So what would work? Would, say, a 50 or 55mm macro lens work - perhaps with extension tubes? This might be a dumb question but I have never owned a proper macro lens so I don't know what they will and won't do. Certainly my tests indicate that a 50mm non macro won't 'see'the full frame of the slide with my crop sensor. I would not be against buying a macro lens if I can also use it for regular close up work.

https://shuttermuse.com/how-to-calculate-mfd-of-a-lens-with-an-extension-tube/

Tells you what the MFD could be for a 50mm lens. As I understand it now you like to copy full frame slides (135 film) to Canon APS size. That is roughly a 63% size reduction. The example given there for a 50mm 1.8 lens at 71% reduction (extension tube added) gives an MFD of 206mm.

A macro lens has advantages if it is best at 0.5 to 1 magnification. Enlarger lenses usually are designed for 1:10 scaling (135 film). There is a 60mm macro and even a Canon 35mm macro lens for APS but I guess a secondhand Sigma EX DG 50mm 2.8 EF mount is less expensive, about $100, and more universal for macro work and will cover FF if you ever want to upgrade. It has a switch for AF/MF which is handy in that kind of work. No need for an extension tube, goes down to 1:1. I have one and it is excellent for film scans and for reflecting originals on a copy table. If used vertically with MF it can slowly change focus, I use a piece of painter's tape to fix the focusing ring then.

Met vriendelijke groet, Ernst
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