Bolex H16 EL and compatibility with 35mm photographic lenses

[Tassanee Duca]

Good morning, and Merry Christmas.

I have a Bolex H16 EL, with adapter for Nikon 35mm photographic lenses. Some time ago I read on a forum (I think on this one, but I haven't found any more traces of it) about an existing problem with the coupling of photographic lenses on Bolex cameras.

In the post there was reference to a focusing problem using these lenses at the widest apertures, so I would like to have more details on this problem, especially starting from which aperture the problem no longer exists.

Finally, since I intend to have this camera modified for the Super16 format, I wanted to get some opinions from those who have a 16mm Bolex and have already made this modification.

I thank everyone and once again Merry Christmas.
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[Jon O'Brien]

Merry Christmas Tassanee! I have a Super 16-modified Bolex Rex 5 camera, with Nikon adapter mount that screws into the C mount on the turret. I've used a Nikkor 50mm f1.8mm lens to great effect with this camera. The thing about reflex Bolex cameras is that they have a prism, between the film gate and the back of the lens, that deflects some of the light coming in from the lens into the reflex viewfinder. This prism, located only a few mm inside the front of the camera, unfortunately alters the optics of the light getting to the film. Thus Bolex reflex cameras need special "Rx" lenses that are made for these cameras, which can compensate for the effect of the prism.

However, there are ways to get around this if using non-Rx lenses. One way is to film with the non-Rx lens stopped down to at least f4. Another way is to use lenses 50mm or longer in focal length. So a Nikkor 50mm lens should be fine to use but of course for 16mm it is a telephoto lens. But you will need to shoot tests, of course, to be sure. I've found that the look of the Nikkor lens for a 16mm Bolex is very good. All the best with your EL!

Edited December 26, 2023 by Jon O'Brien

[Ben Ericson]

17 hours ago, Jon O'Brien said:

But you will need to shoot tests, of course, to be sure.

Agreed. In my experience, lenses become visually softer in the view finder when the sharpness is being effected by the prism. Depending on the amount of experience you have with the system, this is potentially easy to spot. 

I've seen F3.3 as being the official f stop where softening occurs. The effect is more pronounced on wider lenses. For example, the Century 3.5mm or 5.9mm...

The Kern RX lenses are the best for the Bolex. The 26mm 1.1, 10mm 1.6, and the 18 - 86 being my favorites.

[alexandre favre]