The lens and other problems in Super 16 conversions.
Some Super 16 conversions are not up to par and somewhat confusing to the filmmakers as to lens and viewfinder coverage of S16 frame. Short focal length lenses made for the 16mm film cameras and having F stop ratio number 1: 2. or higher (1: 2.8 ) are not likely to cover S16 frame. If the lens mount of converted camera is not centered with the optical axes of S16 frame the problem gets worse.
See below the illustration of the lens coverage of Super 16 and 16 mm frame. The lens orientation is not the only problem concerning the good operation of the converted S16 camera but it is the most important.
Execution of combined small details can make a big difference. Focus distance and alignment of the Viewfinder system is also creating problems in some S16 conversions.
16mm frame vs. S16 frame
1)This frame shows the area of 16mm frame cropped for HD viewing.
2)This is a
full Super 16 frame cropped
for HD viewing. Compare images 1
and 2 for benefit of using the Super
|16mm. lens coverage
This image shows the lens coverage and the orientation of 16mm and S16 image area.
The lens mount is moved to the optical center axes of Super 16 frame.
This image shows the difference if the lens mount of the converted camera is
is left to its original position. The same lens that barely works for above illustration will not cover the S16 frame. The solution is to use a larger lens.
35mm SLR camera lens will do.
Use of a good quality 35mm SLR lens is a good alternative for
Bolex Super 16 cameras.
Bayonet lens mount is an ideal construction for use with 35mm camera lens. The adapter made for bayonet mount takes rough handling and is strong to maintain a correct mounting distance using long focal length lenses.
There is an adapter available for mounting a Canon FD or Nikon F lens to Bolex C-mount. This approach is little riskier, C-mount was designed for smaller and lighter 16mm camera lenses, using these bigger SLR camera lenses the turret plate can get bent, therefore changing the mounting distance out of proper focus.
How does the 35mm camera lens
work with 16mm Bolex H body film camera?
I tested with two SBM Super16 camera. Using 2pc. of 25mm lenses and 2pc. of 50mm. lenses. First test included one EBM having
a Canon 25mm FD lens mounted using a BX-FD & FL adapter and the other EBM having a switar 25mm. lens mounted with a
bayonet to C-mount adapter. When focusing both cameras to same distant target the view angle and image coverage was the
same by visual inspection in aperture gate and in the viewfinder of both cameras.
The second test using 50mm focal length lenses in the same procedure, yields the same result. In conclusion, using the 35mm. camera lenses with 16mm film camera, the excess area of the view will get cropped off by the aperture frame size, that is if the
lens mounting distance is correct for corresponding lens.
When 35mm SLR camera lens is used with appropriate adapter made for Bolex Bayonet mount or C- mount camera,
the lens works the same as used with SLR camera. What you see in the viewfinder is what goes to film gate.
All lens controls, F: stop and focus settings work. Using properly collimated lens, infinity is in focus.
Note1: Bayonet to Canon FD & FL adapter does not work with Canon EF lenses made for EOS cameras.
Note 2: Bolex C-mount Zoom lens does not work with C-mount to bayonet adapter.
Lens modification for JK Optical Printers and Bolex H16 Reflex cameras.
POE Zoom lens.
Kern Vario-Switar 1:1.9 f=16-100mm
POE lens modified for manual operation.
This modification simplifies the lens operation and makes it useable with Bolex EL, SBM and EBM cameras. This fast lens covers
Super 16 frame. Electronic iris is replaced with the mechanical iris diaphragm, F stop value scale and adjustment ring provided.
Modification: US$ 339.00
Selection of good quality
short focal length lenses for Super 16 format.
I have tested all listed lenses, using a Kodak lens test reticule. All lenses registered the same number of line groups.
The details and sharpness of smallest group of lines was interpretable. In my opinion the Cooke and 26mm Switar registered the
sharpest image and a 25mm Switar the worst.
Switar Preset f=10mm 1:1.2
Computar f=12.5mm 1:1.3
Switar f=25mm 1:1.4
Cooke Anastigmat f=25mm 1:1.4
Angenieux Type S42 f=25mm 1:1.4
Kodak Ektar II f=25mm 1:1.9
Kodak Ektar f=25mm 1:1.4
Macro-Switar Preset f=26mm 1:1.1
Resolution of TV lenses made for industrial imaging specifications (not commercial) are comparable to a
good film camera lens. These C-mount lenses are made for industrial custom application and need to be
re-collimated for Bolex Rx 16 C-mount distance.
Computar 12.5mm 1:1.3 Optical layout include 4 single elements and 2 Achromatic elements.
This lens is collimated for Bolex Rx mounting distance.
For the price you can not go wrong with this lens. $125.00
Note that the F: stop is less than f:2 in all listed lenses, which indicates that any fast lens, having a large
diameter rear element is a good candidate for S16 use.