C mount users in here?

Started May 15, 2011 | Discussions thread
leafinsectman
Contributing MemberPosts: 763
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Re: ...and again
In reply to Jonas B, Jun 4, 2011

Hi everyone,

Not sure if you've all received answers to your various questions but here goes...

Jonas B wrote:

So you are saying that even if the lens is further away from the sensor than it is supposed to be everything can be fine thanks to adjusting the focusing ring? Does the lens sit securely in the adapter (not to few threads used)?

The lens will sit securely in the adapter even without filing it down and removing the right screw lets you focus to infinity (and beyond infinity although it wouldn't be in focus anymore). Removing the screw also lets you go further towards the other direction and this (along with not filing the lens down) will allow you to get much closer to your subject than if you didn't remove the screw and file it down.

apicius9 wrote:

Hi Jonas, removing the stop screw works for my 25mm and the 12.5mm Computars, I never filed anything on them.

I was also able to do this same 'trick' with my 25mm f/1.3 Computar lens

johngraham wrote:

Thank you leafinsectman.

No problem, happy to help

johngraham wrote:

Please let me know which of the four screws your removed to make the lens focus so that I can try it again.

I just had a look at my lens and its the one just underneath the "∞"-sign. It's the same with my 25mm in case anyone was interested.

Jonas B wrote:

But... when we discussed these lenses, sometimes in detail, over at GetDPI everybody sat in their kitchen filing off the rear outer millimeters of these lenses to make them fit, and sink down into, the adapters. I just checked mine 25mm and sure, I have filed it.

Yeah, when I did a search I couldn't find anything on it. So I started filing it down and someone made a comment about the screwes in some random forum so I gave it a shot with my second copy and it worked!

Jonas B wrote:

Aaargh - you should have let us al know back then!

Haha yeah, I know. I was keeping an eye on this thread too but I've been busy at work for the last couple of days and when I came back I saw you guys talking about filing the lens down

fermy wrote:

Could it be that all c-mount lenses allow adjusting infinity focus?

Not sure. I have a Cosmicar 25mm f/1.8 and a 6mm f/1.2 and those had to be filed down, I couldn't make it work any other way.

With regards to prices, Angenieux lenses sell for a few hundred dollars whenever I see them up for auction on eBay. The Computar lenses I see on eBay are usually "buy it now" so it's hard to know how much they would sell for as an auction.
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