Arri 16 BL and Bolex H16 Focussing Issue
Posted 09 October 2009 - 12:45 PM
In case of Bolex H16, the issue is after setting up the diopter, the tape measure and the deep focus distance are never the same. We then decide to go with the deep focus technique as it is more reliable as the zoom lens we are using is very old and is not very well calibrated too. With deep focus the issue is when we deep focus a subject and then when we zoom out we loose some focus after a particular focal length. Another thing that is an issue is that when we Rack Focus or Shift Focus then while we move the focus ring, at times the zoom ring and aperture ring also moves.
With Arri BL the issue is when we do a rack focus the focus ring moves to fast or is not very smooth. Is that because if lot of wear and tear of the lens. Whats the possible solution for making it work smoother.
Help will be deeply appreciated.
Posted 09 October 2009 - 03:43 PM
If tape focus never matches eye focus, that means that either the lens needs work or the camera's flange focal depth needs to be reset.
The lens on the BL sounds like it needs work to tighten up the focus ring.
Posted 09 October 2009 - 03:53 PM
Posted 09 October 2009 - 06:12 PM
I am not an optics technician but I can say with certainty that if you want both of these lenses to function at a more professional level, then you are going to have to send them to a lens technician who can properly service them. Both lenses probably need to be re-collimated/re-shimmed after decades of use; and the other lens with the loose/unsmooth focus ring probably needs to be disassembled and cleaned around the barrel. There are others here with much greater knowledge of lenses who can provide you with more specific information about what needs to be done.
The bolex issue isn't necessarily just the lens. It could be the lens mount on the camera. The best way to sort it out is to take the bolex and any affected lenses to a tech and let him decide what needs to be done. He can tell you in 10 seconds whether the flange focal depth is off on the bolex.