Nowadays, there are many lenses available on the market online. After the digital cameras came out lenses leave the camera bodies for being sold separately.
Not everybody, seller and/or buyer, is aware of the difference between the lenses designed for Bolex non-reflex and reflex cameras (H16 SB, SBM, EBM and EL are the later reflex cameras as in the models having the Reflex-written nameplates such as the RX or REX series in short.).
Unfortunately, the Bolex designation system was poor until the model letters have appeared on the nameplates. They have also used the French catalog code system having words, as well as numbers.
The reason that Bolex cameras are sought-after is their build quality and durability, otherwise most models are designed for amateur use.
Somebody may find a clock-work camera untouched since many years (such as even of the 30’s make!) still works without frills. Also no electronics are involved in those.
So, its important to take the following into consideration:
* For a NON-REFLEX Bolex, and other makes all the AR coded lenses, whether its made by Kern or not (such as Nikon CINE-ROKKOR), are OK (mounts can be in C, or B e.g. bayonet mount).
** For a REFLEX Bolex, then the right choice is the (H 16) RX coded lenses, whether its made by Kern or not, for shorter than 50mm (included), as well as the RX compatible zooms made by Kern, Angénieux, SOM-Berthiot and sopelem (mounts can be in C, or B e.g. bayonet mount). All other longer lenses, incl. the AR lenses, can be used.
sopelem has also made the same zooms under the Rank Taylor Hobson name.
In fact, the Flange Focal distance or FF distance in short (the distance between the lens seat and focal or film plane) of AR, RX and C-mount lenses is exactly the same and 17.526mm.
Reason for that: The fat Bolex beam-splitter prism pane between the lens and shutter – That pane makes the FF going back ⅓ of the thickness of the pane. The diffraction of the light going thru that is not equal for each color (RGB). So, the pane makes each color of the image focused not in the same point. That phenomenon causes the spherical aberrations.
Light loss due to the prism! So, take an exposure reading with the effective (adapted) exposure times instead of photometric (by the way, the EL model has a built-in TTL meter), or use the Bolex Exposure Meter specially made by GOSSEN. The Bolex cameras use different max. opening shutter angles depending on model. Always check the proper manual!
Alternatively, use a zoom having the built-in TTL metering provision made by Kern, or Angénieux (an early Bolex Diaphragme Automatique model). These zooms will get the correct effective exposures needed, as well as allow fully automatic, semi automatic and manual exposure settings.
Manufacturer’s statement for the Kern Switar RX fixed-focal length lenses is as follows:
Although specially corrected to take into account the prism for capturing the light in the reflex viewfinder on Bolex cameras, they give excellent results on standard cameras (not provided with a prism), provided you do not use diaphragm openings greater than f/2.
However, if you should use the RX lenses having some specific focal lengths (mm) on non-reflex models, as well as the AR lenses having some specific focal lengths (mm) on reflex models, the aperture settings wider than f/4 should be avoided to eliminate possible out-of-focus issues.
AR stands for antireflet (anti-reflection) in French, although all the RX lenses have anti-reflection coating natively.
The lenses made specially for the Bolex H8 series may be identical to those for the H16. They are C-mount lenses with different FF distance. Beware for H16!
Kern lenses were made by Kern & Co., Ltd., Aarau, Switzerland
SOM stands for Société d’Optique et de Mécanique de Haute Précision
sopelem stands for Société d’Optique, Précision, Electronique et Mécanique