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Author Topic: FP20 drifting focus Jeff Else Expert Film Handler Posts: 125 From: Detroit, MI, USA Registered: Nov 2006 posted 01-16-2010 05:32 PM                     One of my FP20's likes to slowly drift out of focus so that i have to correct about every 10 minutes. Focus is sharp and uniform when correct, but always drifts. Why??  |  IP: Logged Ian Parfrey Phenomenal Film Handler Posts: 1049 From: Imbil Australia 26 deg 27' 42.66" S 152 deg 42' 23.40" E Registered: Feb 2009 posted 01-16-2010 05:52 PM                     Jeff. Could be a number of things such as -: Lens loose in the mount Too much heat at the gate with corresponding "popping" of the focus Slop in the focus leadscrew Worn skates and runners There may be other possibilities which I'm sure other tech's will point out. Good luck with it and let us know how you go and what you find. Cheers Ian  |  IP: Logged Jeff Else Expert Film Handler Posts: 125 From: Detroit, MI, USA Registered: Nov 2006 posted 01-16-2010 07:41 PM                     the lens is certainly in there tight, and the skate and runners are pretty new. the gate feels cool to the touch... i've got a 1200 cfm fan on two machines running 2k each (probably overkill i know but it was a free fan). is too much heat still a possibility somehow... if not, what can i do to fix the slop in the focus leadscrew?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-16-2010 08:15 PM                     Remove the lens and shake...verify it is not unscrewing itself. Verify that your focus rack is operating smoothly and not binding mechanically or is gummed up. Remember, it is a spring that moves the lens one way so if it has a problem...there may be a time-delay between adjusting the focus and when the lens finally finishes its movement. Steve  |  IP: Logged Jeff Else Expert Film Handler Posts: 125 From: Detroit, MI, USA Registered: Nov 2006 posted 01-17-2010 05:19 PM                     the spring is gunk free, is lightly lubed, and is moving freely. do you mean shake the screw without the lens mount in the holder? i did that and the screw does jiggle a bit.. perhaps it is just unscrewing itself? do i need a new screw?  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 01-17-2010 10:00 PM                     No...shake the lens, itself. Steve  |  IP: Logged

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