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C mount adapters lens fitting ( How to )

Discussion in 'Adapted Lenses' started by felicedenigris, May 4, 2013.

  1. felicedenigris

    felicedenigris New to Mu-43

    8
    Oct 7, 2012
    Hello Mu-43 community,

    I recently just purchased a C mount type lens.It is a Cosmicar 25mm 1.9. I also purchased an adapter seperately for my olympus omd-em5. However I noticed that the lens doesn't fit adapter's radius. So my real questions of concern are, did I purchase a wrong C mount lens? Is it common for users to sand down or bore out the adapter radius to fit the lens? I thought C mount lenses would fit C mount adapters?
     
  2. manzoid

    manzoid Mu-43 Regular

    137
    Jun 9, 2011
    I think with c-mount lenses it sometimes depends on the specific lens/adapter combo.

    People often either 'machine'/file down the rear of the lens or adapter.

    I remember some adapters being reviewed and I believe this one was regarded as one of the best:
    C5 type C mount lens to M4/3 M43 Micro 4/3 | eBay
     
  3. felicedenigris

    felicedenigris New to Mu-43

    8
    Oct 7, 2012
    Kind of steep $$$

    Hmm, that definitely looks like a really advanced adpater and very capable. The price hints at that too. Although I'd be very scared to purchase it and then encounter my lens doesn't fit. But it looks promising. I sanded my previous FOTGA adapter and it's very inconvenient. I ended sanding the threads and I can no longer use it. With the nC5 type C mount lens to M4/3 M43 Micro 4/3, looks like I don't need to sand anything?


    This is what i used: Amazon.com: FOTGA C Mount Lens to Micro M43 4/3 for Panasonic: G1, GH1 GF1, G2 G10 Olympus: E-P1, EP-2, E-P1L Mount Adapter Ring Lens Mount Adapter: Camera & Photo
     
  4. manzoid

    manzoid Mu-43 Regular

    137
    Jun 9, 2011
    Yeah... I am not too sure.

    I experimented with a few cheap cctv lenses and if they didn't fit, I sanded down the rear of the lens ever so carefully. I didn't want to buy an adapter that cost more than the lens, especially if it wouldnt work, as you say.

    Not to discourage you but I rarely use these lenses any more. I think for the wide to normal range it is probably better to buy a native lens, even something like the old olympus 17mm 2.8. People like the sigmas too.

    Anyway, sorry if I can't give you the answers you want. Good luck.
     
  5. Petrochemist

    Petrochemist Mu-43 Top Veteran

    652
    Mar 21, 2013
    N Essex, UK
    Mike
    I've just received my second proper c mount lens, a Fujian 35mm f1.7 (to add to an equally cheap 25mm 1.4).

    Unlike the problems here I find they both need to be unscrewed by 1½-2 complete turns to focus as close as infinity. This is with any of my 3 c mount adapters. anoyingly neither the lenses or the adapters seem to be parfocal, so I'll have to have a different shim for each lens/adapter combination I'm going to use. (Definitly worth dedicating the adapter to a lens, whilst I had been planing on using the spares for creating some bellows mounts.

    I've managed to make a shim that is close to perfect for the 35mm, but it doesn't leave much thread holding the lens on!

    Amoung the other 'c mount' lenses I've tried are a 6mm that screws into the adapter OK but doesn't seem to be able to focus at any distance - I suspect it's a CS lens, and is too far away from the sensor to focus on something touching the lens. Coming with this lens free was another unidentified 'c mount' that has no thread and is slightly smaller than a c mount. I've seen telescope eyepieces that are something like 0.96" diameter, it might be one of them. The pair were cheap enough that it's not really worth forking out the postage to return them, but I'm not sure if ill be able to come up with a use for them.:frown:
     
  6. Just Jim

    Just Jim Mu-43 Top Veteran

    941
    Oct 20, 2011
    If it's to tight, find a local shop that does tap and die work and have them re-thread the adapter. They should be ble to measure, and rethread it. Although it may only specificly fit that one lens afterwards.
     
  7. RobWatson

    RobWatson Mu-43 Hall of Famer

    Maybe it is just me but I'd never advocate getting a lens then an adapter unless there is a proven example with remarkable qualities. I already have a collection of non MFT lenses (c-mount and FF nikon, etc) so getting an adapter so I can use my old friends is a different matter.

    I'm never going to buy a non-native lens to adapt just because I can ... there has to be a really compelling reason for that. Maybe y'all have compelling reasons - cool.

    Just recognize that there is way more to getting a lens onto the camera than the back focus distance which is all the adapters do (mostly). As described most adapters seem to err on the side of too little back focus so focus at infinity and beyond is the result. I have several fine c-mount lenses that simply do not fit and never will without extreme modification (sanding does not count as extreme). In some cases modification of the camera body would be required.
     
  8. Just Jim

    Just Jim Mu-43 Top Veteran

    941
    Oct 20, 2011
    I like C mount swirlies...
     
  9. ekoe

    ekoe Mu-43 Regular

    73
    Sep 26, 2010
    Hello guys. I suspect the C-mount adapter review Manzoid referred may be mine, as I highly recommended the original Hawk Peng C5, and I stand by that assertion and the others here: Flickr: Discussing Accurate adapter and other c-mount observations in C-Mount on Micro 4/3
    The first thing I want to share is that anytime you adapt a lens to another mount, it should be adjusted or at least checked to confirm accurate focus. This is crucial if you want infinity focus and accurate focus marks. It's simply due respect to the lens to adapt and adjust it properly.
    Second, there are likely a thousand or more models of c-mount lenses, and not all will fit on a particular C-mount to m4/3 adapter. C-mount has a shorter flange focal distance than m4/3, which means the lens must sit within the M4/3 lens port by a few millimetres. Not all of them fit. Some need machining.
    By this point, nearly every C-mount lens available has been tested on m4/3. We know what fits m4/3 adapters, we know what needs to be machined. If you're unsure, google 'ekoecamera' and ask me. I don't mind. I don't like to see users purchase lenses that will not cover their sensor, or can not be properly adapted.
    The one thing I would like to request is to stop the DIY lens 'hacking'. Cameras are disposable, our lenses are not. Please seek a reputable lens service technician to modify and adapt your lenses for you. There are many generations of shooters who will seek out these lenses, please do not dremel or grind. Have them properly adapted by a competent lens service technician. Personally, I would rather modify a lens at a cut rate than to see one of my beloved old cine lens models DIY hacked.
     
  10. Crdome

    Crdome Mu-43 Hall of Famer

    Sep 11, 2011
    West Central Indiana
    Chrome
    From the chart, you will see that in most examples the FL needs to be at least 25mm for a decent coverage.



     
  11. Petrochemist

    Petrochemist Mu-43 Top Veteran

    652
    Mar 21, 2013
    N Essex, UK
    Mike
    I was well aware that it wouldn't give full coverage, (that's quite common with fish-eye lenses anyway) but thought it worth it if the angle of view is significantly wider.
    As I can't even get near focusing I'll not be able to tell.