C mount lens

exe163 · Joined: 18 Mar 2009 Posts: 16 Location: California, USA

Hi everyone,
As I stated in another thread I am going to bet a E-P1 when the the 17mm kit comes out. Something I find interested is C mount lens: they can be adapted to m4/3 bodies with adapter. Notice c mount's register distance is lower than m4/3, which is 20mm. From what I heard it's not a problem since the adatper intrudes into the camera body. There will be vignetting due to the slightly smaller image circle.

Anyone know anything more about c-mount lenses? I am looking at something =< 25mm and =<f/2. A quick search on ebay tells me c mount lens is not as cheap as they use to be for obvious reason.

dino1 · Expire: 2014-08-21

Not much interest here on C mount lenses.
Have a look at getdpi.com 4/3 forum where they talk about little else.
You need to be a bit careful with C mounts.
If the diameter of the rear flange is greater than around 36mm you will need to machine a step on said flange to allow the lens to seat properly on the m4/3 c mount adapter.
I recently found a gorgeous little Angenieux f1.3 15mm but found it only projected a dismal circular image on my G 1.
I've also been dissappointed with similar problems with a selection of
Computar TV camera lenses.
Having said this I've been delighted with a Dallmeyer f1.9 2 inch c mount lens. Razor sharp at f1.9 and as near as damn it full coverage on the m4/3 sensor. Only cost �1 (the Angenieux was expensive and cost a massive �3).
I also suspect C mount lenses have rocketed in price recently .
I did a search on ebay and could not believe what I was seeing.
There were 2 examples of the 15mm Angenieux, one had a buy it now of �183 and another was well over �200 .
dino1

exe163 · Joined: 18 Mar 2009 Posts: 16 Location: California, USA

Zeiss Tevidon cost over $600!

http://spreadsheets.google.com/pub?key=p9kkgjwEQQQ-HJwvNDobeEw

I believe if you want full coverage 25mm (1") is the widest you can go. I am not sure what you mean by diameter of the lens; I thought it's well defined by the name of C mount much like F mount, Eos, M42, should it be a set standard with same register distance and diameter of lens?

I found some rather inexpensive TV lens on Taobao (chinese ebayish market place). I probably give it a shot since most lens cost close to nothing.

dino1 · Expire: 2014-08-21

Yes C mount thread and register are standard.
However if the overall diameter of the rear of the lens is greater than aprox 36mm it will not mate correctly with a 4/3 adapter .
There is a thread on the forun I mentioned entitled Hacking a C mount lens which explains this fully.
dino1

wilson.c · Joined: 18 Jan 2010 Posts: 363 Location: Hong Kong

I came across some lenses from a discarded old CCTV installation. Checking the mount it fits the C-Mount specs, but the register says it's a CS-Mount which is 12.52mm vs 17.536mm (C-mount). I wonder if there's a CS-Mount adapter for m43?

kds315* · Expire: 2021-03-09

Think about it Wilson: If CS mount has a register of 12.5mm and a mft camera has about 20mm -
what could be expected and why make an adaptor for that? 2ndly, CCTV lenses maily serve 1/3 or 2/3" camera
sensors, whereas mft needs 21mm image diameter... Wink

wilson.c · Joined: 18 Jan 2010 Posts: 363 Location: Hong Kong

Thks Klaus,

You have a point there Wink

I did some tests on my C-mount to mft with one of these lenses and although there's alot of vignetting the image is quite sharp in macro mode due to the register distance. Maybe it's just gonna be for cropped macro use eh?

kds315* · Expire: 2021-03-09

...or as a door stop or paper weight?

Fun aside, they can always be used reversed for large magnification macro (old trick) since then the sensor is fully covered.