What focusing helicoid adaptor for my new old lens?

[mjmountain]

Hi - could do with a bit of help

I have an enlarging lens on the way. I bought it as a bit of fun, It's an Industar 90u 75mm. It has an m42 adaptor already fitted, I was going to just use my m42 to mft adaptor to mount the lens on my MFT Olympus. I now realise that the lens is fixed focus and as such would benefit from a Focusing helicoid m42 to mft adaptor. I also read that on certain adaptors it can get perilously close to the sensor stack.

The question is - which size will get me the best from the lens, and if possible allow focusing to infinity?

Don't want to end up buying unnecessary kit, or with a Macro lens with a tiny working distance.

Many thanks

Mike

 

[Petrochemist]

You shouldn't have any issues with the lens getting close to the sensor stack. I'd expect the lens to be about 70-80mm from the sensor for infinity focus - enlarger lenses usually have a rear focal distance similar to their focal length. You'll want a reasonable amount of extension beyond the infinity position, and extra 75mm would give it macro focusing capability, but that's overkill for everyday shooting

You could get a long helicoid I think 35-90mm would be a good match for a 75mm lens on MFT. I'm not sure if these are available with a MFT bayonet but there are short M42 adapters specially for helicoids (some combined with c-mount adapters) allowing any m42 helicoids to be fitted.

If your planning on adapting other lenses then I think it makes sense to get a helicoid that will allow M42 to focus to infinity - there are some MFT-m42 versions that specify they give infinity focus - and add a second m42 helicoid (or simply extension tubes but they give less flexibility) that give you another 25mm at their shortist.

This doesn't work out much more than combining a single helicoid with a standard adapter and gives much more flexibility.

IIRC 25+ helicoids are around £20, 35-90mm ones are ~£30. the short MFT-M42 adapters are around £5...

 

[Nod]

SRB Griturn would be the people I'd speak to about any adaptors I wanted. Might have changed their name (maybe SRB Photographic these days?) but I reckon Google would find them.