Using 35mm Photo Lenses

This section deals with the specifities of shooting 16mm. film with 35mm. photographic lenses (technically the 24x36mm format).  These lenses are available in a variety of mounts, most commonly Nikon and Canon.

NOTE FROM JASON: I’ve posted most of the info here about using 35mm lenses and have had good success, however recently I started to notice that in very bright conditions, some Nikon lenses cause a large hot-spot in the center of the image.  I’ve verified this on two separate cameras.  Some theories are that lenses with a very large rear element can cause reflections back against the mirror which create the hot spots on the image.  I can’t seem to reliably re-produce the problem so I can’t say for sure but if you are using 35mm lenses, it would be great if you’d post some comments about your experience.  If you wind up with some footage like this, it is fairly easy to fix with a radial color correction filter.

As an introduction, a couple of reminders to clarify an often confusing topic :

A bit on optics :

The Focal Length of a lens is determined by its optical design and does not vary.  A 50mm. lens remains a 50mm lens whether it’s mounted on a large-format still camera, a 35mm. film camera or a 16mm. film camera, etc.

The Focal Coverage of a lens is also defined by its optical design and will not change either : if a lens covers an area wide enough to imprint a photographic 24x36mm. format, it will of course cover any smaller formats.  But if a lens is designed for a 16mm. camera, it’s unlikely that it will cover a much wider format without vignetting.  This is particularly true of wide-angle lenses, and is the main problem with finding cheap lenses for a Super-16 modified ACL, for instance.

What does change when the negative (or sensing) format changes is the Field of View (FOV), in other words, how wide an angle one particular lens will record on different formats (or how much of your subject will fit onto yor neg at a given distance).  So long as the field coverage is enough, a larger sensing area (or negative) will mean a wider field of view

The Depth of Field (DOF) of a given focal length at a given aperture also does not change.  BUT since the FOV changes, covering a given area with a lens in one format means changing for a lens of a different focal distance to cover the same area (or moving the camera backwards or forwards accordingly), which will in fact change the depth of field.  In other words, it’s the change of lens or the change of distance that changes the DOF in this case.

A bit on Formats :

Both 35mm. still cameras and 35mm. film cameras use 35mm. film : this is the result of a revolution in photography popularized by Leitz with the Leica series, which borrowed negative from the film world and adapted it to photography, ushering in truly portable modern photography.  However the two formats are very different because the film in a still camera moves horizontally (‘landscape’ mode) while it moves vertically (‘portrait’ mode) in a film camera, resulting in a much smaller image size in the latter.

The photographic 35mm. format is technically known as the 135 format, or 24×36 (the dimension of the image in mm.).  The film 35mm. format varies depending on the gates on cameras but is basically 22x16mm. or less, depending on the actual format (Academy, Widescreen, etc.).  Thankfully, 16mm. film has a simpler history and only comes in a few formats : Regular 16mm., Super-16, Ultra-16.

Now, providing that you have the adapter to mount the lens on a camera properly, you may of course use lenses designed for a larger format (like 24×36 photo) on a smaller-format camera, like 16mm.  In fact, shooting with 35mm photo lenses is a very economical way to build a collection of primes – especially so if you already are shooting 35mm still film and have a collection of lenses.  If you don’t already have a set, good quality lenses are very cheap nowadays, particularly if you go with photographic mounts that are considered obsolete (42mm. screw mount, for instance) or lenses without the AF electronics needed for modern cameras.  These all also make great lenses for shooting super-16 since they easily cover the wider frame, still only using the center of the lens, which is generally of better quality.

While the same may seem true of 35mm. film lenses, the fact that these lenses are infact often a lot more expensive than 16mm. lenses make them far less appealing as an alternative.  Of course, if you own the lenses, you may use them in much the same way (relative to their negative size).

There are a few limits to consider, however :

Manual Focus & Aperture

The best 35mm photo lenses for Eclair cameras are older, fully manual lenses. Newer AF (auto focus) lenses are fine on an Eclair camera as long as they have a manual focus ring and a manual aperture ring (you simply don’t benefit from the automatic capabilities of the lens).  Almost all 35mm lenses have a manual focus ring, however some newer designs may not have a manual aperture ring.  Digital still cameras control the aperature internally and so there is no manual control on the cheaper lens built for them.  You cannot use lenses without an aperture ring because you have no way to control the f-stop – i.e. how much light is coming in.

The bottom line – only buy lenses that have both a manual focus ring and a manual aperture ring.

Cropping Effect

Because of the difference in negative size between the photo 24x36mm format and film formats, a lens’ focal length doesn’t produce the same visible results on cine cameras as they do on 35mm still cameras (see Optics above).  The FOV varies with the format change, and because a ‘standard’ lens is defined as one that has a focal length of roughly the size of the diagonal of the negative, you get something like this :

• For 16mm film,  50mm is a telephoto, 25mm is “normal” and 10mm is wide.
• For 35mm photography, 105mm is a telephoto, 50mm is “normal” and 20mm is wide.

As you see, the focal length needed to cover the same angle of view for 16mm cinematography is roughly half of its 35mm photography counterpart.  Shooting on a 35mm still camera, a 50mm photo lens looks normal.  But when you put that same lens on your 16mm film camera, it will look like a telephoto and you’ll have less of your subject in the frame.

Wide-angle coverage

As a result of what we just said, while it’s fairly economical and easy to collect a variety of high quality 35mm primes for your normal and telephoto range, you will have a problem with wide-angle lenses.  In the 35mm phototagraphic world, a wide-angle begins at 35mm. focal length, a 28 is still common, but lenses as wide or wider than 24 or 20mm are extremely rare and expensive : there is so much more negative to cover on the 24x36mm format that you reach the same optical limits in lens design as you would below 8 or 5mm. in 16mm. cine format. As a result, you would pay a small fortune to buy a wide-angle photo lens that would produce images that are not wide at all (40/50mm.) a 16mm. film camera.

About Lens Mount Adapters

The first choice is an adapter that was designed specifically for the ACL’s TS-mont.  Eclair only made a (now very rare) Nikon to TS-mount, but others can be custom-made by good camera shops.  Les Bosher in the UK will build a custom adapter for pretty much any lens mount you need.  Electro Optical House in the USA produces PL adapters and possibly others as well.  Other techs that specialize in lenses may produce them as well.  Contact info can be found on the resources page.  TS-adapters are relatively expensive because they are custom-made and people who ordered them generally keep them.  If you find one, however you pay for quality : these adapters will allow perfect critical focus even during a zoom and will most likely outlast your camera.

The second choice is to use a C-mount lens adapter.  These are manufactured new and can be had on ebay for under $50.  You simply screw them into the C-mount on your camera.  If you’re using Nikon lenses, for example, you just get a C-Mount to F-Mount adapter. Overall, many people have reported success with these C-mount adapters.  They are fairly cheaply made and contain plastic parts, but they’ll get the job done.  Primes are fine, but you may have problems with critical focus during zooms depending on the particular adapter’s fit with your camera.  For $50 it’s not really a major investment.