Author Topic: C moutn adapotor  (Read 140 times)

scottmei

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C moutn adapotor
« on: October 05, 2017, 04:22:56 AM »
Hi guys, this is my first post here, and received my Chrono 1.4 camera few days back, and purchased a fotodiox C to B4 mount adapoter to use my Zeiss Digi Zoom lens, but after screwed up the adapter, it becomes upside down. so when I mount the lens on, the lens is also upside down which won't be able to put the lens support underneath.

I tried the adapter on other c mount camera, but the adapter is correct. so I wonder if the CS to C mount adapter has a different thread count than usual camera? I have a brand new 16mm vintage eyemo camera bought from an auction as a collector item.

if the thread has different count on the Cs to C mount adapter, would it be possible to talk to technician at krontech to solve this issue? thanks. I appreciate any inputs. thanks!

tesla500

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Re: C moutn adapotor
« Reply #1 on: October 06, 2017, 12:04:11 PM »
Hi Scott,

Check if your adapter has a facility to rotate the C mount relative to the B4 mount, sometimes you need to loosen a few screws to do this. If it doesn't support that, you can install the adapter on the camera, then loosen the set screw on the bottom of the camera using the included allen key. This lets you rotate the entire mount ring and lens/adapter assembly relative to the camera body. You can then re-tighten the set screw with the lens oriented correctly. Not that this will effect backfocus, you'll need to check your backfocus after doing this, and potentially rotate the lens by full turns to get the backfocus set properly.

As far as I know there is no standard orientation for a C mount, the lens will end up at an arbitrary rotational position when installed. Some lenses such as the Computar 12.5-75mm can be rotated relative to the mount to correct this, by loosening a black ring near the lens mount.

David

Simon

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Re: C moutn adapotor
« Reply #2 on: October 06, 2017, 10:01:08 PM »
I have a fotodiox C to EOS adapter and the same thing happened to me (and I freaked out until I saw the adjustment screw David talks of) that allowed me to rotate the lens.

scottmei

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Re: C moutn adapotor
« Reply #3 on: October 06, 2017, 10:36:36 PM »
thank you David and Simon. i will give it a try. thanks.

BiduleOhm

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Re: C moutn adapotor
« Reply #4 on: October 07, 2017, 04:37:30 AM »
Quote
Some lenses such as the Computar 12.5-75mm can be rotated relative to the mount to correct this, by loosening a black ring near the lens mount.

Do you know the correct way to unscrew the rear ring because mine seems to be very very tight and I don't want to put force on the focus/zoom/exposure mechanical stops (unless it's the right way to do this) so it's hard to grab the body of the lens.

scottmei

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Re: C moutn adapotor
« Reply #5 on: October 08, 2017, 01:45:00 AM »
Quote
Some lenses such as the Computar 12.5-75mm can be rotated relative to the mount to correct this, by loosening a black ring near the lens mount.

Do you know the correct way to unscrew the rear ring because mine seems to be very very tight and I don't want to put force on the focus/zoom/exposure mechanical stops (unless it's the right way to do this) so it's hard to grab the body of the lens.

I simply made a mark on the adapter and the attached my lens then unscrew the Allen key at the bottom, then just turned the Cs mount to the desired position then tighten the screw. it seems easy enough, but have not yet checked back focus yet. I am sure there will be some adjustment needed since my lens is long and heavy. my set up is let the camera sit on the lens, bit the other way around.

BiduleOhm

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Re: C moutn adapotor
« Reply #6 on: October 08, 2017, 03:13:14 AM »
Of course I already adjusted the back focus, I have the lens rotated about 90 of what it should (I guess it's better than before the back focus adjustment where it was nearly 180 out, but it's still very annoying) but I can't correct it with the back focus adjustment because it would throw off the back focus.