PD-170 Focus Issue
 

I've noticed that my PD-170s will drift out of focus even when in Manual. It seems to be more noticeable when for example, capturing a wedding processional where the subjects are approaching the camera.

This effect was documented by Alan Barker: "Second, in MANUAL focus the PD-150 tends to drift out in the middle of the zoom range then drift back in at the wide end. The age old procedure of zooming in, focusing, then zooming back to your desired focal length does not hold for the middle of the zoom range."

Does anyone have any suggestions for getting around this mid-range fuzziness?
Bob

My 150's certainly don't have a focus during zoom problem. It sounds like the back focus on the lens isn't optimized and a trip to Sony might solve the problem. Call their 800 support line and see if they'll solve the problem at no cost.

The term I've always heard for this effect/defect is 'breathing,' not drifting which gives the wrong mental picture to someone used to the old terminology. A drifiting focus is one that 'drifts' out of focus with no user changes to the lens.