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Josh Bloomer

Dark spots affecting final image

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I recently received a Bolex H16 Reflex along with a Vario Switar 100 POE lens and Cine-Velostigmat 2” f1.5 C-mount lens. It used to belong to my grandfather and until now has been boxed up and untouched for probably decades. The main mechanisms still run and appear to be working fine. I flipped out the prism on the camera and noticed a few small specks, but nothing I would have thought would be significant enough to produce the spots seen in the image. There are also some particles seen from the viewfinder, but what I see in the viewfinder I don’t see any signs of to that extent on the prism itself, and don't show up at the same locations they do on the processed film. So I went in thinking it wouldn’t have any affect on the final image itself.

Viewfinder - Dust Particles

I shot a roll of film to test the Bolex out, but noticed several dark spots on the image when it was processed, especially in shots using the Cine-Velostigmat lens. The spots became sharper and more prominent as the f was increased. I looked at the lens itself, but didn’t see any obvious signs that I thought would have produced anything this bad.

Final Image from Cine-Velostigmat Lens

Cine-Velostigmat Lens

I also shot with the Switar lens. What’s interesting is that the image is much cleaner. I can detect very slight dark spots but they are much more out of focus compared to what I see from the other lens. I also noticed, though, that the Switar has all these spots on the back of it. However, since the image it produced wasn't nearly as affected, this makes me think this isn't the root of the issue.

Final Image from Vario-Switar Lens

Vario-Switar Lens

This was my first time shooting any kind of film whatsoever, let alone operating the Bolex. Does anyone have any insight/educated guesses as to what might be causing these dark spots, or how I might be able to further troubleshoot? Aside from what I did, I don’t really know what else to look out for. I’d be happy to give out more details or take more pictures of the equipment. Any help would be appreciated - thanks in advance!

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Make sure both sides of the beamsplitter prism are clean and dust-free. Dust on the rear of the prism can show up on the image when the lens aperture is stopped down. 

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I ran into a very similar issue with my bolex. At first I thought it was the lenses, but it was most definitely the prism. As Jean-Louis pointed out (Both he & Dom Jaeger helped me tremendously with this.) keep your prism as clean as you can, and try not to stop down to f/22 if you could help it, the variable shutter is helpful for this. 

To clean the prism, I used Kimwipes and some Pancro lens fluid, I only sprayed it once on a folded kimwipe and wiped each side of the prism once in one direction. Do not scrub and do not spray the lens solution directly on the prism, spray onto the wipe. 


This seemed to help my my issue. 

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