problems with my lens

[Joe Zakko]

shot a short on my bolex this past summer. shots using my 10mm kern palliard lens had something in the bottom right corner. It's dark, but reflects light when hit directly. Not sure what it is. luckily, i composed for 2.35:1, but i really hope there's not something wrong with my lens. Anybody have any ideas what it is, i'd really appreciate it.

 

here are a few shots where you can see it best.

 

http://www.youtube.com/watch?v=EGo_cE8YPcc

[Tom Jensen]

Some kind of vignetting going on. Could be the behind the lens filter tray. Is the turret seated in the right position?

[David Auner aac]

Is the turret seated in the right position?

 

That was my first thought too. Hard to check now though... So if you can recreate the effect looking through the finder. Your Bolex is a Reflex, right?

 

Regards, Dave

[Bernie O'Doherty]

Joe,

 

You could try removing the filter holder. Then flip the turret around so that you can get at the prism block. Pull out the prism so you can look directly through the aperture plate to the film plane. Release the spring tension by running the camera until it stops. Push in the stop/start button to the locked-on position. Slowly move the movement by turning the film sprocket gears by hand until you have a clear view through to the aperture plate. You should have a clear optical path. Look for a film chip somewhere, blocking the light path top-left, (shows on image bottom-right). Check that the prism block is clean and not chipped.

 

Cheers, Bernie

[Dom Jaeger]

I'm pretty certain it's a long lens in the bottom port of the turret that got in the 10mm field of view.

 

I was thinking film chip too at first but the "reflects light when hit directly" line and the fact it only occurred with the 10mm made me think again.

 

It's a classic turret camera problem, led to some interesting camera designs to overcome it like the diverging turret and Bell and Howell's Spider Eyemo:

 

http://www.golden-agetv.co.uk/img/equipment/159s.JPG

[Joe Zakko]

Yeah, I posted this elsewhere, and they said it was a long lens in the field of view. Turns out, I purchased my 100mm lens after marking the groundglass, so I never noticed that it was in the frame. Pretty embarrassing, but I'm glad I figured that out. Thanks for the replies.

[Tom Jensen]

You know, I thought the same thing but forgot to mention it but it did look like two separate issues, the vignetting and the lens. At first I thought it was a finger. But, a very good call, Dom.