Extension tubes?

[Terao]

What are the options for using extension tubes on either an LTM or M camera? Are any still available new? I'm looking to build a custom lens adapter (need to increase the flange to focal plane distance a fair way) and it occured to me that a set of tubes may be a good starting point. What size options are there? Doesn't matter whether they're LTM or M tubes, although I'm thinking LTM tubes will be easier to work with in conjunction with an LTM-M adapter (the aim is to mount the lenses on an M body)...

One other thing - what's the spec for the screw thread - I'm no doubt going to need to get a machine shop to cut one at some point...

 

[jesse1dog]

Have a look at eBay item: 270136815194.

There's a set of rings and a focusing screen.

 

[laptoprob]

Bellows show up from time to time, not really hard to find.
Why do you want the hassle to do this with a rangefinder? This is SLR territory!

 

[Terao]

Not intending using the tubes for their normal use (I have a GR-D for macro), just as a quick/cheap way to hopefully prototype this new adapter I'm trying to build. Whatever I get I'm going to need to butcher the lens end to mount the lens so I was hoping to find some cheap tube options that might just happen to be the right length.
Bellows is definitely an option but they tend to be a bit expensive to destroy for a prototype.

 

[Graybeard]

You can find a set of LTM Russian extension tubes on eBay for about $10 for a set of three different lengths, this will be the most economical option.

If you plan to use the extension tubes in a static arrangement, such as copying documents or photographing stamps or coins, you might consider the Focuslide device. This is slow to use but they are inexpensive and perfectly satisfactory. These are also quite inexpensive. I've used one on an enlarger stand, temporarily removing the enlarger head and mounting the Focuslide in its place.

Remember that when using expension tubes without TTL metering, you'll need make exposure corrections. The old Leica manuals generally have a table of these corrections.

It happens that the Focuslide was originally designed by Norm Goldberg, the father of Don Goldberg of DAG camera repair fame.

The LTM thread is a peculiar hybrid of metric dimensions and English threads. The diameter is 39mm but the threads are 26 or 24 tpi (my memory fails me here). This is convenient for a machinist in the US or UK as the threads can be cut on a non-metric lathe. I've made rings and adapters on a South Bend lathe here in the US.

One story is that Leitz chose this odd combintion to make it difficult for third party suppliers to provide lenses to fit Barnack Leicas.

 

[Terao]

Thanks Graybeard, looks like its 26tpi. Handy wikipedia page here:

http://en.wikipedia.org/wiki/List_of_lens_mounts

 

[Gabriel M.A.]

Yes. Extension tubes.