Zeiss CP2 EF Shaking on C300 mount

[Roger Pinto]

I recently attempted to use a remote follow focus (wireless option) mounted on my Zeiss CP2 EF to C300.

when focussing medium to fast motion and when changing the focus direction the lens shakes slightly at the marrying point of camera and lens. I checked all screws of lens and c300 all are solid tight. How to solve the problem as its very annoying to see the shake happening with each focus direction change. I never noticed this with manual follow focus device of my rig.

Any views will help...

[Chris Malley]

Not experienced with remote follow focuses however if I were to give my thoughts it could be something to do with the amount on torque being transferred onto the lens. If it's occurring during medium/fast changes in focus it could be doing it with a lot of power.

If theres a way of changing some of the settings on the remote FF to reduce torque or even changing some of the pinion gear ratios (if it even has that!). I have experience with semi-professional RC car racing, so it may well be utter rubbish i'm on about.

[Jim Martin]

Which wireless FF unit are you using? Arri, Chrosziel, RedRock?

Jim Martin
Filmtools.com

[Roger Pinto]

Its from Senna a croatian company. Google it for their other products as well. I wonder how to counter the torque which these gears are prone to exert on lens.

[Craig Chartier]

Yikes, from what I saw on the YouTube vids of this system, those motors are way too beefy for small primes, looks like it was designed for zooms, old Russian zooms, made out of brass. Maybe try running the battery down? Or adding an in line pot to drop the voltage to the motor?

[Christopher Young]

Short of a very low drag focus drive that puts little rotational or lateral force on the lens I don’t see a simple solution given the design limitations of the DSLR type lens mounts of today.

Unfortunately the EF mount was never designed for the sorts of applications we are putting them through today. Inside the EF mount there are a set of tensioning leaf type springs designed to hold the lens flange mount flush with the body flange mount. In most cases this does the job perfectly well.

This type of mount was designed years ago and adapted by most bayonet type SLR film camera makers in one form or another. The mount was designed to take the weight of a manual type mid-sized lens. Or conversely if using a long lens the lens was usually supported with its own tripod mount and the camera flange mount only had to support the weight of the camera body. In general this design philosophy worked fine with SLR cameras as there were no large lateral loads or rotational loads applied to the lens or mount.

With film cameras it was a totally different story. We had the likes of the standard Arri mount, the PL mount and many others but in all cases they were designed as a solid precision metal to metal locking mount with no room for movement as with the leaf spring type tensioning mount.

I had a similar problem using an MTF B4 mount adapter that has an EF to E mount connection. The spring tensioning in the EF mount side of the equation would allow movement. Once I had the adapter supported solidly with a 15mm rod support it now became an integral part of the bridge plate attached to the camera. All movement had disappeared.

What I am getting at is that I would be looking to see if there is a way to support the lens solidly with some kind of support mount to make it an integral part of the camera body. I think your problem would then go away.

Chris Young
CYV Productions
Sydney

[Roger Pinto]

Originally Posted by Christopher Young

I had a similar problem using an MTF B4 mount adapter that has an EF to E mount connection. The spring tensioning in the EF mount side of the equation would allow movement. Once I had the adapter supported solidly with a 15mm rod support it now became an integral part of the bridge plate attached to the camera. All movement had disappeared.

What I am getting at is that I would be looking to see if there is a way to support the lens solidly with some kind of support mount to make it an integral part of the camera body. I think your problem would then go away.

Chris Young
CYV Productions
Sydney

I am very eager to see the mount or a way around to get over the shaking issue. I am stuck with EF mount as C300 + Zeiss CP2 are both EF :( wished if i had gotten a PL mounting body & lens ... may be next purchase of camera would also involve a EF mount of CP2 to swap with a PL mount. BUT so far I look for a solution ... Would you be able to support your idea with any pictures !

[Sabyasachi Patra]

Do you have other lenses also shaking?

I don't think it is a mount issue. The EF mount is strong enough to handle my long lenses. It works fine with the Canon 70-200 f2.8 L IS II lens with 2X TC as well as with 100-400 lens when I mount the lenses directly. I only mount the super telephoto lenses with support.

If the rubber sealing behind the L series lens gets worn out, then there may be chances of shaking. No idea why the zeiss CP2 shakes. I guess it may be due to the wireless follow focus and not a Canon or Zeiss issue.

[Craig Chartier]

Before putting any more time into thinking the lens mount may be the issue I would goto a major rental house and mount up a higher end wireless follow focus unit. There is a reason that the dampend motors on other models cost so much. If you dont have any issues with a higher end system then its most likely not the lens. Zeiss EF mount is much stronger than the standard Canon stills mount. IF you still see issues on your camera with the CP and another focus unit. then try another camera body and rule out any issues with your C300. You might have already damaged your body with that massive motor. I have used the CPs on 5D's with Bartech wireless units running around on steadicams and have had no issues. We also had high end FOX motors.

[Christopher Young]

Not sure about Zeiss but Canon have for years made what they call 'tripod mount rings.' See pic of one mounted on one of their 100mm lenses. There is also a quick pic of the MTF EF adapter on my FS700 with the weight of a B4 broadcast lens mounted. Push and pull all you want on the lens and there is no movement between the camera body and the lens support mount. There is also a pic courtesy of MTF of an extreme case of lens mount support.

With a suitable mount ring and the camera body all securely mounted on a rail / rod / plate system you virtually eliminate any movement between the two. Any lateral or rotational movement put into the lens is isolated from the body and lens mount hence no movement. Canon, Nikon, Minolta et al made a host of these mounts even for their short lenses. There is no doubt they are the best way to eliminate movement at the lens mount.

Think of a mount ring holding the lens and you turning the focus or zoom ring. All the energy involved in that process gets transmitted to the mount ring not the lens mount.

Do a Google images search for 'tripod mount ring’ and you will find numerous types of mounts and manufactures. I feel pretty sure a suitable lens mount in conjunction with a good rod support system and bridge plate would cure your problem.

Chris Young
CYV Productions
Sydney