Changing Mounts Question

[steve green]

Hey guys,
I'm changing back to PL mount after a brief job with my Canon mount. I've gone through the back focus adjustment with the #10 torque screw on the top of the brain and was wondering if there's any other adjustments to be done. The back focus looks good (focus is sharp throughout zoom) and I'm still going to bring it into the rental house on the prep, but right now the footage scale is taping off "long". Three feet reads 3' 2", six feet reads 6' 8" on the lens and the further the distances, the further out it is. Is there a flange focus adjustment, would a Red Focus device help with this? Any help always appreciated!
Steve

 

[Stephen Williams]

Hey guys,
I'm changing back to PL mount after a brief job with my Canon mount. I've gone through the back focus adjustment with the #10 torque screw on the top of the brain and was wondering if there's any other adjustments to be done. The back focus looks good (focus is sharp throughout zoom) and I'm still going to bring it into the rental house on the prep, but right now the footage scale is taping off "long". Three feet reads 3' 2", six feet reads 6' 8" on the lens and the further the distances, the further out it is. Is there a flange focus adjustment, would a Red Focus device help with this? Any help always appreciated!
Steve

Set up a PL mount with proper equipment , your zoom is probably off. A known good wide angle 18mm or less at infinity will give you a good idea.

 

[ericyoung]

The Epic Brain Torx screw back focus adjustment IS the flange focus adjustment. Note there is actually a protective Torx screw on top of the actual adjustment Torx screw which needs to be removed while adjusting, so you may not have been actually adjusting anything.

Depends what PL lens you are using, and is that your only lens, or is it part of a set? Will you be renting other lenses?

Cheap PL lenses may not have accurate lens barrel distance markings. In that case, if your zoom looks sharp and can focus at infinity at all focal lengths, and you aren't trying to match other lenses in a set or other rented lenses, you are good to go.

If you have a lens set, and this is the only one which is out, get your zoom lens checked by a lens tech or the manufacturer. Although it's possible your other lenses and/or camera body are incorrectly adjusted relative to the correct PL FFD of 52mm.

The Red Focus device allows you to adjust the camera body's FFD to the correct PL specification of 52mm. You can then use the camera body to check if your lenses are within specification, and if they are not, then get the lenses adjusted.

http://matthewduclos.wordpress.com/2009/05/30/focus-on-back-focus/#more-16

 

[Dave Blackham]

We use an IBE device and always check PL collumation. We also use regularly use Optitek Nikon Mount, A mount with PL, Nikon, Leica R,, M42, and Canon FD and also Canon EF mounts. Whats very apparent is the mounts do need setting up correctly if they are changed, no 2 PL mounts are the same it seems.

As a rough rule if you remove and re fit a Red PL mount it can usually be relied up on to be correct on refitting but it is bad practice not to check. If you remove the mount and fit any other mount even if its of same manufacturer and type Id put money on the mount not being correctly collimated.

To be honest Im not sure if there is a multi mount columation device made, I think Jarek may have something suitable.

Its a real issue with more glass with diferent mounts now being used for Photography/Cinematography.

 

[steve green]

The Epic Brain Torx screw back focus adjustment IS the flange focus adjustment. Note there is actually a protective Torx screw on top of the actual adjustment Torx screw which needs to be removed while adjusting, so you may not have been actually adjusting anything.

Depends what PL lens you are using, and is that your only lens, or is it part of a set? Will you be renting other lenses?

Cheap PL lenses may not have accurate lens barrel distance markings. In that case, if your zoom looks sharp and can focus at infinity at all focal lengths, and you aren't trying to match other lenses in a set or other rented lenses, you are good to go.

If you have a lens set, and this is the only one which is out, get your zoom lens checked by a lens tech or the manufacturer. Although it's possible your other lenses and/or camera body are incorrectly adjusted relative to the correct PL FFD of 52mm.

The Red Focus device allows you to adjust the camera body's FFD to the correct PL specification of 52mm. You can then use the camera body to check if your lenses are within specification, and if they are not, then get the lenses adjusted.

http://matthewduclos.wordpress.com/2009/05/30/focus-on-back-focus/#more-16

I'm bringing the camera to the rental house and they tell me they can check the back focus on their collimator. BTW, do you know anything about the Red Focus? Is is very easy to see back focus issues on it? If I change the mount two or three times a year is it work the $?. Nice informative article, thanks Eric.

 

[ericyoung]

If you're going to the rental house, bring your lenses and your camera and get them both checked out.

Not used the Red Focus personally, so can't say. But the principle is simple, so can't see why it wouldn't work fine.

As to whether it's worth it, probably only if you or your clients will rent PL lenses to use in combination with your own, as then you/they would want to be able to interchange them without altering the camera PL FFD every time you change lenses.

If you only ever use your own lenses with your own camera, it's less critical.

 

[Björn Benckert]

I'm bring the camera to the rental house and they tell me they can check the back focus on their collimator. BTW, do you know anything about the Red Focus? Is is very easy to see back focus issues on it? If I change the mount two or three times a year is it work the $?. Nice informative article, thanks Eric.

We got the red focus and it's very easy to use. strap it on like a lens. push the button, zoom in on the touch and use the torch to dial in the backfocus. Ours was quite far off when we received our epic. And since then we have been changing mounts like mad but the focus seems to stay the same. So after using it once it's more of a nice pice to have in the lens case when rental clients start's to complain about backfocus... then it's just to pull it out and they soon realize that it might be that big old zoom they rented some place else that might be a bit out of dial.

 

[steve green]

We got the red focus and it's very easy to use. strap it on like a lens. push the button, zoom in on the touch and use the torch to dial in the backfocus. Ours was quite far off when we received our epic. And since then we have been changing mounts like mad but the focus seems to stay the same. So after using it once it's more of a nice pice to have in the lens case when rental clients start's to complain about backfocus... then it's just to pull it out and they soon realize that it might be that big old zoom they rented some place else that might be a bit out of dial.

Thanks, Bjorn, I always rent PL lenses when using the PL mount so I think the investment in the Red Focus is warranted. Like you say, good to have in the lens case when you need it!