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Where to get a helicoid with inner diam of at least 44mm?
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PostPosted: Sun Dec 29, 2013 4:46 pm    Post subject: Where to get a helicoid with inner diam of at least 44mm? Reply with quote
The rear part of my Rodenstock 75 is quite tiny, ∅ is about 44mm and length about 35mm.
Where to get a helicoid with this inner ∅ and length?
(it might be a nice way to focus this lens)

Last edited by mesinik on Sun Dec 29, 2013 4:49 pm; edited 1 time in total


PostPosted: Sun Dec 29, 2013 4:47 pm    Post subject: Reply with quote
Or should I think about a bellows?
After all, is bellows a good option at all to focus a 75mm lens?
If so, the middle part of Rodenstock has ∅ of about 6cm, it would be better to get a bellows with this inner diameter (such a large helicoid probably does not exist).


PostPosted: Sun Dec 29, 2013 4:48 pm    Post subject: Reply with quote
Could any broken objective be turned to a helicoid broad enough?


PostPosted: Sun Dec 29, 2013 6:19 pm    Post subject: Reply with quote
Some macro x2 converters make good helicoids once the glass is removed. I have got a Teleplus MC7 Macro X2 one that extends by 18mm on the helicoid, the inside dia' of the Canon FD mount is 48mm, which I think might be maintained if the glass and all the other stuff was removed - which I haven't done. You can find them cheap on ebay in most camera mounts.
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