Gretag 120 Tube Lens Tested With Surprising Results

[Miljenko]

Did you also need to sand down the knurled lip on the front of the lens? My M52-M50 adapter doesn't fit over it and I can reverse thread the adapter on from the other side.

Basically, I never touch the lens itself if there is a way to fit by modding adapters. You got it right, both 50-52 adapter rings have to be screwed in from the lens back side. Just make sure the tube that goes towards the front end has to be wide enough internally to clear that lip. It measures 49.4mm.

[kaleun96]

Thanks for the advice on this Miljenko. I chose an expensive solution in the end but that I think it's better suited for this purpose than either the extension tubes or the SM2 tubes.

I got Raf's 50mm bore x M42 threaded clamp adapter to use for the rear and his M50 x M42 threaded adapter for the front. The clamp has a diameter of 50mm but Ray Parkhurst had mentioned it fits this lens well. It's also 25mm in length so long enough to take up the length of the rear part of the lens without reaching the 50mm thread.

The M50xM42 adapter is also longer than normal at 28mm in length. This is enough to take up the 14mm of the front part of the lens plus another 14mm of the 20mm of M50 thread on the lens body.

This then gives me female M42 on the lens front and male M42 on the lens rear with only two adapters. That suits me a bit better than having multiple extension tubes with added M50-M52 or M50-SM2 adapters. The only caveat is that I need to file down a fraction of a millimetre from the knurled lip on the front of the lens. This doesn't bother me much and shouldn't be difficult.

I had come across some interesting adapters such as the one below on eBay but I could never work out if both ends with M52 threaded or only one end was.
https://www.ebay.co.uk/itm/52mm-Lens-Ad ... 1209832846

[enricosavazzi]

[...]
I had come across some interesting adapters such as the one below on eBay but I could never work out if both ends with M52 threaded or only one end was.
https://www.ebay.co.uk/itm/52mm-Lens-Ad ... 1209832846

Difficult to say for sure, but this part is generally described as "55 mm adapter tube". It is not clear whether 55 mm is the diameter of the male thread of the adapter, or the length of the adapter. Judging from pictures, the tube length less the male thread looks less than the diameter of the M52 female thread at the front, and the male thread diameter slightly wider than the 52 mm female thread, so probably this adapter cannot be used as a 52 mm extension tube.

What you want is something like https://www.amazon.com/Photo-Plus-52mm- ... XEFF310TX3

[Miljenko]

Enrico,
if you check few posts back, this is exactly the same adapter Cam asked about. And it is part of extension set I recommended (https://www.amazon.co.uk/Fotodiox-Exten ... cs&sr=1-10). Incredibly enough, the whole set is cheaper than a single tube!
It is a tube with I.D. of 49 mm, with 52mm male thread on one side and 52mm female thread on the other.
I have 4 sets so I should know :-)
I have permanently attached one of the sets to Gretag 120mm lens.

[kaleun96]

Thought I'd update everyone on the mounting option I went with. The Raf adapters arrived and worked exactly as expected. It took only 5-10 minutes with a small hobby file to reduce the diameter of the front lip to fit the M50mm adapter. I don't mind the silver-on-black look either.
I also really like how the adapter threads butt right up against the lens, reducing the distance between the element and a stacked lens or camera sensor by as much as possible.





Front with adapter
Rear with adapter