Focus changing when zooming !?!

Soliton

Soliton

Well-known member
A couple weeks ago I took about 70 shots inside the USAF Museum outside Dayton, OH. I should have taken a night vision setup, that place is very dark.
So, I just got around to capturing tonight and see that I've got a big problem with the cam (100 not A). After carefully focusing at full zoom in, a lot of shots are way out of focus. Some shots are crystal sharp. Others start focused and go out while zooming out. The clear shots are nearly all non-zoomers.
I was at 30P and focus set to manual anyway. Looking closer to see what was happening I can see that as the lens widens the focus varies unevenly through the shot and ending up looking as if its in close focus instead of 85-99 where it started. And, in one shot it just jumped out of focus near the end of the pull back. But I possibly bumped the ring as I was handheld the whole time..
Fortunately this was only a pleasure trip for me, so not a great loss.
I imagine you guys are going to tell me to send it in for service, but I've got to ask if anyone has heard of this sort of problem or knows a quick (spelled 'cheap') fix?
 
You may have a back focus problem (see the back focus thread). Maybe the problem is that it was just too dark in there, though the problem shouldn't be that big when going wide angle. If you normally (under more favorable lighting circumstances) don't experience it then it might not be very serious. Did you have auto iris on? If it was set on auto, and you were zoomed in on a well lit object, it might open up automatically when zooming out (trying to compensate for darker areas), thereby diminishing the depth of the focus. I hope it won't be a big problem.
 
Yes I had auto iris on. That would explain some of what I see.
Thanks for pointing to the other thread - looks like I've got it too. I'll send it in and have the rough spots sanded down ;)
Thanks again.
 
You must log in or register to reply here.
Back
Top