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A question on enlarger lenses and infinity focus


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I just borrowed an enlarger lens (metal EL-Nikkor 50mm f/2.8) and I would like, whenever possible, to make use of it for portraits on a Nikon D70.

It is a bit unclear, however, which focusing helicoid should I get to achieve infinity focus or at least a reasonable working distance (two to three meters would be fine).

Looking on the net, I see there at last four M42 adapters (to adapt via a M39 to M42 ring and then to a M42/F mount one):

12-17mm, 16/17-30/31mm, 25-50mm, 35-90mm.

 

Anybody can help?

 

Best regards,

 

Andrea Festa

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Put the lens flush to the camera mount and look through the finder. This represents more or less the maximum focusing distance you can get with the given lens. You might be able to seat the lens a little deeper inside the camera throat, but not by much as it will interfere with reflex mirror and the stop-down actuator pin.

 

You will rapidly see the 50 EL-Nikkor cannot focus to infinity on the D70. Adding adapters will only making it focusing even closer. The 63 mm EL-Nikkor can just barely reach infinity and for this needs a customised mount so it can be sunk into the camera throat as far as possible. Get the shortest focusing adapter you can get for your 50, but don't expect miracles.

 

On a general note, enlarger lenses never were designed for infinity focus and even when you can get to infinity, image quality may be rather questionable. The 63 mm f/3.5 does pretty well, though.

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Andrea, in order to focus any lens to infinity, you must mount it at the proper distance from the sensor plane. This distance is called the "flange focal distance" or "register distance". Each camera and its lenses have a different flange focal distance.

Reference: http://en.wikipedia...._focal_distance

 

Nikon F-mount has a long flange focal distance of 46.50mm. But the Nikon enlarger lenses (ELs) were not made for the typical Nikon camera body. So their flange focal distance varies.

 

I can get my new version EL-Nikkor 80/5.6 to focus at infinity on a Nikon camera when mounted on an intermediate zoom helicoid of 17-30mm (approximately) in length. This is because the 80/5.6 has a FFD of 70mm, so 46.50 (Nikon) + 23.50 (from the helicoid) = 80mm.

 

Unfortunately we have had trouble trying to discover the FFD of other Nikon EL lenses. This is partly because enlarger lenses were never designed to be used "at infinity" in the first place.

 

The FFD for micro 4/3 camera bodies is 19.25mm, so you have a better chance of an enlarger lens achieving infinity focus on a m4/3 camera body by using one of the zoom helicoids found on Ebay and usually made in China or Hong Kong. There are typically short, medium, long and extra-long versions of these zoom helicoids offered (as you have noted above). I have three for my m4/3 camera. They are not terribly expensive, but do look carefully on Ebay because the prices seem to vary. And nearly as I can tell they are all similarly manufactured. I just pick the currently least expensive source when I need to buy one. So far they have all been good and worked well.

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Unfortunately we have had trouble trying to discover the FFD of other Nikon EL lenses. This is partly because enlarger lenses were never designed to be used "at infinity" in the first place.

 

Info posted here B)

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