Bolex - Eclair "C" mount

[avr]

Are they the same lenses Bolex C mount and Eclair C mount.?

Are complatibles bolex-eclair lenses to each other?

thanks

[Gwgon]

Yes, bolex (c-mount) lenses can be used with Eclair cameras. There is adaptors to use nikon lenses with c-mount.

PAX

[David G. Smith]

A "C-mount" is a "C-mount". Just realize, that the base of a C-mount lens is just a very few screw threads and that long lens need stabilization with rods and clamps. The C-mounts were the "Pro-sumer" lens of their day and were never state of the art. Don't get me wrong, they were OK lenses, but they were never great lenses.

[Barry_Green]

Also, keep in mind that some Bolex lenses are "RX" mount. Meaning they physically will mount in c-mount, but they're designed specifically for the Bolex Reflex cameras.

[dop16mm]

actually, the eclair npr needs rx mount lenses, not standard c mount used on older non reflex cameras. All of the adapters, arri, nikon, etc work fine, but if you want to use a lens from a bolex it needs to be rx. I have an old non-reflex h-16, and the lenses will not focus on my eclair, but lenses borrowed from Rx-5 work fine. I don't know about lenses made for other cameras like bell and howell, try before you buy, tough on ebay, but there you go.

[avr]

actually, the eclair npr needs rx mount lenses, not standard c mount used on older non reflex cameras. All of the adapters, arri, nikon, etc work fine, but if you want to use a lens from a bolex it needs to be rx. I have an old non-reflex h-16, and the lenses will not focus on my eclair, but lenses borrowed from Rx-5 work fine. I don't know about lenses made for other cameras like bell and howell, try before you buy, tough on ebay, but there you go.

Hi tahnks for your info, you told about Eclair NPR ,is this applicable for the ACL 1 cameras?

[Bill__Turner]

For the record: (and perhaps more than anyone wants to know)

There is a very slight difference in the "in air" flange focal distance of the Bolex Rx and standard "c" mt. The original non-reflex Bolex Camera's were standard "c" mt, meaning the image focused 0.690 inches (17.52 mm) behind the mounting surface of the lens.

"c" mt is a standard that goes back a long ways and is mechanically a one inch pitch diameter, 32 threads per inch thread.

The Bolex Rx Camera uses a prism type beamsplitter so the light must pass thru a small block of glass to form an image. This both changes the location of the image (it moves back approximately one third the thickness of the glass - the exact amount depends on the index of refraction of the glass in the beamsplitter) and also affects the image quality, primarily at short focal lengths and higher apertures.

Bolex sold special Rx mounted lenses in the 10mm , 16 mm , 26mm and 50mm focal lengths that were optically corrected for the prism. These lenses are marked Rx on them.
Once this distinction was made, lenses for the standard "c" mount, non-reflex Bolex were marked "AR". Lenses made prior to the advent of the reflex camera carried no special coding.

The equivalent focus of the Rx mounted lense was approx .0025" shorter than standard "C" mount. This would mean that a 10mm Rx lens might not quite achieve infinity focus on a standard "c" mount camera . Bolex concluded that for focal lengths over 75mm no differentiation was required due to the depth of focus and higher f numbers.

Angenieux Zoom lenses for the Bolex Reflex were coded "type C" and had a silver rear piece marked "Rx".

It is possible (if memory serves) that some very early Bolex non-reflex lenses had threads longer than current practice (which is less than 4 mm in length- approx .160") and may not fit properly on some c mt cameras such and the Beaulieu , Eclair, etc that do not all allow them to screw in far enought to seat properly.

In my opinion, based on customers experiences, the optical differences in image quality were small and Century routinely refocused Rx lenses for Standard C mt use and C mt lenses for use on Bolex Rx cameras. I never remember a customer complaining about the results.

Bill Turner
Schneider Optics
Century Division

[kplo]

The Eclair (all of them) used standard C mount lenses in addition to the Eclair mount. Even the adaptors (Nikon to C, etc) are made to the standard flange/focal distance (6.90 in. as Bill indicated above).
However, some long lenses in Nikon and other mounts actually focussed beyond infinity (for infra-red, etc.), so with those you needed to be a tad more careful with the infinity focus.
Hope this helps.
Ken

[dop16mm]

thanks for the info on the distinction. I know my bolex is old, from the 40's I think, so I checked my lenses and they are marked AR and not unmarked as the pre rx would be. I do know they will not focus on my eclair npr, but Rx lenses work fine.