Pulling focus on stills glass
Posted 31 August 2013 - 05:20 PM
I've been looking into Contax Zeiss 25 and Rokinon 24 to use on my super 16 camera. Both of those lenses' witness marks start from 2 -3 ft and then Infiniti. Is there any trick to tape measure and pull focus on those lenses?
Posted 31 August 2013 - 07:30 PM
Using a follow focus with a higher gear ratio (either one specifically designed for short throw stills lenses or with the ability to change drive gears) will increase the effective throw at the control knob, where you can mark focus distances on the disk. The disks are interchangeable, so you can have ones dedicated to each lens. Obviously the quality of the follow focus, in terms of back-lash and rigidity, will have an effect on how accurately the system works.
Unfortunately with some stills lenses, the mechanics of the focus mechanism itself can have back-lash, so even with the best follow focus unit precise focus pulls can be hard to achieve. A discrepancy might creep in when the direction of the focus turn changes. You'd need to test each lens to see how bad it is.