8mm Forum: hell and bowell zoom lens

This is topic hell and bowell zoom lens in forum 16mm Forum at 8mm Forum.

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Posted by Clyde Miles (Member # 4032) on April 27, 2014, 07:04 AM:

i have the black zoom lens f1.1.3 32-65mm that has suddenly started giving me out of focus pictures. everything was fine until recently, but now when i focus centre of picture sides are out of focus and vice versa. there is no fungus and lens is clean and scratch free. any ideas would be much appreciated.

Posted by Dominique De Bast (Member # 3798) on April 27, 2014, 01:14 PM:

I have the same problem with some projectors. The problem is not linked with the lens (it happens with different lenses on the same projector) but with the framer (if it is the correct word in English, I mean the piece of the gate that presses the film toward the lamp). It needs to be adjusted (something I never tried myself but that should not be difficult to do).

Posted by Clyde Miles (Member # 4032) on April 27, 2014, 02:06 PM:

hi dom, thank you for the suggestion, but i tried this lens on all my other b&h and still the same problem. it just seemed to happen overnight.

Posted by Dominique De Bast (Member # 3798) on April 27, 2014, 05:44 PM:

Clyde, it may be a problem a never came across, yet. I hope other members will be able to help you.

Posted by Marshall Crist (Member # 1312) on April 28, 2014, 10:33 PM:

I seem to remember another thread where it was suggested that a slight adjustment to the tiny screw on the side of the lens would address the problem. I am experiencing a bit of this with my Hell & Bowell lens, but haven't mustered the courage to try fiddling with the screw.

Posted by Clyde Miles (Member # 4032) on April 29, 2014, 09:16 AM:

where's this screw located, can't find one on mine.

Posted by Marshall Crist (Member # 1312) on April 29, 2014, 08:49 PM:

On mine it's on the side, about halfway down the length of the lens.

Posted by Clyde Miles (Member # 4032) on April 30, 2014, 03:25 PM:

since starting this thread ive purchased another identical zoom and this projects perfect. i want to fix my original lens, as there just to good to throw away.

Posted by Paul Mason (Member # 4015) on May 06, 2014, 03:24 AM:

Clyde, From what you describe the loss of all over sharpness must be due to disturbance of internal lens components that provide correction of the aberrations. If there is an adjustment screw it may be behind the outer sleeve. Any adjustment should be done ideally with the lens in place and the projector running a film. Good luck.

Posted by Clyde Miles (Member # 4032) on May 06, 2014, 04:57 PM:

thanks paul, but no screw anywhere on lens

Posted by Paul Mason (Member # 4015) on May 07, 2014, 02:52 AM:

It needs a specialist optical engineer to fix although reducing the effective aperture with an opaque disc with a hole in the middle in front of the lens might work but you lose light of course. Experimentation to find the best trade-off between overall sharpness and light loss would be needed.

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