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Recommended adapter for this lens

Discussion in 'Adapted Lenses' started by soulkeeper, May 11, 2012.

  1. soulkeeper

    soulkeeper New to Mu-43

    7
    May 6, 2012
    Hi to all!!
    I have a canon lens Jx6 11 11-70 f 1.4 from a very old toshiba video camera..from what i"ve found around the net it seems to be a c-mount lens for 2/3.. Is it a c-mount lens?
    Focus and zoom rings looks ok as well as aperture ring.. Any info of which adapter to buy so i can use it with GH2? What about infinity focus? Here is a photo of the lens.. Camera+ photo

    Any help would be much appreciated!

    Thanks!
     
  2. fredlong

    fredlong Just this guy...

    Apr 18, 2011
    Massachusetts USA
    Fred
    If it's designed for 2/3 video it will probably vignette heavily. Even many 1" video lenses vignette, especially at wide angles.

    You can try holding it in front of the sensor without any mount to get an idea if it might work for you.

    Fred
     
  3. soulkeeper

    soulkeeper New to Mu-43

    7
    May 6, 2012
    Thanks for your reply!
    I can avoid vignetting using ex-tele mode on GH2 (28-182 instead of 11-70 as extele has 2,6 crop factor), but i need help about the type of mount the lens is and which adapter to use..
     
  4. ekoe

    ekoe Mu-43 Regular

    73
    Sep 26, 2010
    I have that same Canon zoom J6x11 as pictured.

    It's a c-mount 2/3" video zoom. Should be parfocal.

    You need a c-mount to m4/3 adapter.

    However, the lens will not mount on a GH2 with the servo-zoom and
    auto-iris assemblies. They prevent mounting by obstruction with the
    GH1/GH2 grip and LVF hump, respectively. They must be removed in order to adapt the lens to your GH2.

    The auto-iris removal is the hang-up, as it is connected to the actual lens iris and is sprung. Removal of the motor on these lenses usually disengages the aperture ring.
    You'll need to find a solution there.

    I can help you in little bits if you wish, working along with you on this twin I have in my possession. It can be done, and it would make a nice affordable zoom for ETC.

    Alternatively, you can contact me through my website ekoe camera

    I always offer free advice as a service to the m4/3 community.
     
  5. soulkeeper

    soulkeeper New to Mu-43

    7
    May 6, 2012
    Thanks for the very useful information!
    I"ll contact you asap..
     
  6. ekoe

    ekoe Mu-43 Regular

    73
    Sep 26, 2010
    I've taken a close look at my copy so here's some observations for others with the same lens:

    The servo zoom removes easily by loosening the coin-slotted head mounting screw and sliding the servo toward the back of the camera. The auto-iris assembly is not easily removed, and to do it properly (i.e. without forcing or breaking anything) the lens must be partially disassembled (from the rear) down to the mounting point of the auto-iris assembly.

    This mounting point is between the iris and the zoom mechanism of the lens. At that point, the auto-iris can be cleanly removed and the adjustment arm from the iris to the motor must be cut (preferably with tin snips so no metal debris enters the iris). The auto-iris mounting ring protrudes out from the lens so it must be removed in order to cut out the protruding motor bracket portion of the ring. The auto-iris mounting ring must be used because it serves as a spacer so the zoom ring does not bind against the iris assembly. After cutting, the mounting ring will be c-shaped and will no longer protrude out from the lens housing.

    Removal of the motor does not disengage the aperture ring as I previously mentioned. That is the case with the Sony 11-70/1.4 (which is a very similar lens). This Canon 11-70/1.4 iris functions normal with the auto-iris motor disengaged.

    You will need to fabricate a blank to cover the gap in the lens housing where the mounting ring and auto-iris adjustment arm once protruded. This is the stage I'm at presently.

    This is a pretty involved modification, and I wouldn't recommend it if you don't have the tools (jeweler's screwdrivers, small hex wrenches, tin snips) and at least some experience working on photographic equipment. You'll be working around the naked iris of the lens and whenever the iris is so exposed there is risk of damaging it.

    Ultimately the zoom will require parfocal adjustment in order to hold focus through the zoom after adapting it to m4/3.
     
  7. ekoe

    ekoe Mu-43 Regular

    73
    Sep 26, 2010
    I should also mention that if you'd like to keep the click-stops of the aperture, proceed very carefully when lifting the aperture ring. The bearing is very tiny and will likely tumble out as you lift the ring, so have a dish or pad of some sort to catch the bearing. If you don't catch the bearing, it's unlikely you'll find it again.