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Nikon D40 modified to M42
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PostPosted: Sun Oct 04, 2009 11:25 pm    Post subject: Nikon D40 modified to M42 Reply with quote

I like my Nikon D40 because it does so well with UV photography. However, most of the lenses I use are old M42 or very old Exakta mount. I've been using the Exakta lenses as macros because I couldn't get infinity. The M42 lenses would give me infinity if I used an adapter with a glass optic, but this stole light.

So I converted my Flange Film Distance from the Nikon F 46.5mm to the M42 mount 45.5. I still don't get inifinity with the Exaktas which require 44.7, but I'm close enough to get a lot more use out of them. The M42 lenses are spot-on!

The conversion is 90% reversible. And I can use Nikon lenses still with a Nikon to M42 adapter, as well as many other 35mm lenses.

I had two possible approaches to changing the FFD: move the sensor and prism forward (very hard) or move the flange closer. I chose to move the flange.

First I removed the old flange and bayonet springs, saving them for a possible reversal.

My new flange was made from a very thin M42-Nikon aluminum adapter. I drilled holes for the flange screws, thinned the outer rim, carved away part of the M42 section which would have contacted the Nikon inner surface above the electrical contacts, and carved away a similar space for the diaphragm lever.

The only non-reversible aspect was a grinding away part of the diaphragm lever where the lens would strike it. The lever will probably still work on Nikon lenses.

The M42 lenses are now happy. I have a T-Mount lens that will use the Nikon-m42 adapter. The Exakta lenses have surgical tape around the upper part of the lens mount, above the bayonet, the stop-pins removed, and a 39mm female-42mm male adapter over this, held in place with a single grub screw. This converts the Exakta to M42. Again, still 0.8mm too far away, but in the ballpark.

The joy of lenses as they were intended to be used!

PostPosted: Sun Oct 04, 2009 11:43 pm    Post subject: Reply with quote

Great, great!! You have an M42 DSLR coool! Congrats! Thank you for sharing!