Bolex Lenses

Bolex Lenses

written and designed for the web by Joel Schlemowitz

C-Mount

Bolex lenses are small screw-in lenses, the mount on the rear of the lens makes the lens a c-mount lens.

One basic thing that can seem a little confusing at first, the focal length of the lens might not reflect the actual size of the lens. The 10mm lens is physically longer that the 16mm, and the 16mm and 25mm lenses are the same size.

Older and Newer Lenses

The older Switar and Yvar lenses have a aperture ring without a handle.

The newer lenses have a double handle, one of which can be moved independently to open the iris, the other remaining in place at the f-stop and acting as a brake for the first handle when the lens is closed down again.

The newer lenses are also designed with a rear ring that turns independently of the rest of the lens, letting the lens be mounted with the indications facing any direction. Be aware that this design will allow you to inadvertently mount the lens with the indications facing away (and blocked by the other lenses on the turret) if are not paying attention to this.

RX and non-RX lenses

The Reflex Bolex has a prism between the lens and the film plane. Because of this, differently calibrated lenses are designed for non-reflex and reflex Bolexes.

Reflex Lenses will have the letters: RX

Telephoto lenses are interchangable, and therefore do not need to be RX.

(If you are shooting at an f-stop above f-4, the depth-of-field that comes from closing down the lens will make up for the difference in calibration, and an RX lens can be used on a non-reflex camera and vice versa.)

(See smallmovies site for an essay by Dennis Couzin that goes into some detail on the RX lens and non-RX lens issue: The Truth About The Bolex Prism.)

Macro

Bolex macro lenses will allow you to focus closer than a non-macro lens, for extreme close-up shooting.

To use the lens in its macro range, turn the focusing ring beyond its closest setting. Non-macro lenses stop at this point. The macro lens will keep turning and a red band will appear.

This you know that the lens is in its macro range. (On some lenses this will be followed by a green band as the lens is focused even closer.)

When the red band is present the measurements on the focusing ring are no longer relevant.

Placing the Lenses on the Turret

The lenses should be placed with the 25mm lens (the normal lens) in the center position (as pictured here). This prevents the telephoto and the wide angle lens from being mounted adjacently, which will cause the simple problem of the telephoto lens being visible in the corner of the frame when you shoot with the wide angle lens.

What NOT to see in the viewfinder!

Depth-of-Field indication

The lenses for the Bolex have a built-in depth-of-field indicator, in the form of a series of orange dots that appear as the lens is closed down.

A typical way to utilize this is to set the lens with infinity at the far dot, giving you a depth-of-field from x-distance to infinity (x-distance being the distance of the furthest dot on the other side).

If you are using the dots to determine depth-of-field, be careful that you don’t forget to re-check them when you change f-stops!

The material on these pages may be printed out for personal use only. Use as course handouts only with proper acknowledgment of authorship and the New School's Film Production Department.

[Bolex Main Page] [Joel Schlemowitz Film ProductionPages]

[Joel Schlemowitz Homepage] [New School Film Production]

© 1999 Joel Schlemowitz All Rights Reserved

C-Mount Bolex lenses are small screw-in lenses, the mount on the rear of the lens makes the lens a c-mount lens. One basic thing that can seem a little confusing at first, the focal length of the lens might not reflect the actual size of the lens. The 10mm lens is physically longer that the 16mm, and the 16mm and 25mm lenses are the same size.
Older and Newer Lenses
The older Switar and Yvar lenses have a aperture ring without a handle.	The newer lenses have a double handle, one of which can be moved independently to open the iris, the other remaining in place at the f-stop and acting as a brake for the first handle when the lens is closed down again. The newer lenses are also designed with a rear ring that turns independently of the rest of the lens, letting the lens be mounted with the indications facing any direction. Be aware that this design will allow you to inadvertently mount the lens with the indications facing away (and blocked by the other lenses on the turret) if are not paying attention to this.
RX and non-RX lenses The Reflex Bolex has a prism between the lens and the film plane. Because of this, differently calibrated lenses are designed for non-reflex and reflex Bolexes. Reflex Lenses will have the letters: RX Telephoto lenses are interchangable, and therefore do not need to be RX. (If you are shooting at an f-stop above f-4, the depth-of-field that comes from closing down the lens will make up for the difference in calibration, and an RX lens can be used on a non-reflex camera and vice versa.) (See smallmovies site for an essay by Dennis Couzin that goes into some detail on the RX lens and non-RX lens issue: The Truth About The Bolex Prism.) Macro Bolex macro lenses will allow you to focus closer than a non-macro lens, for extreme close-up shooting. To use the lens in its macro range, turn the focusing ring beyond its closest setting. Non-macro lenses stop at this point. The macro lens will keep turning and a red band will appear. This you know that the lens is in its macro range. (On some lenses this will be followed by a green band as the lens is focused even closer.) When the red band is present the measurements on the focusing ring are no longer relevant.

Placing the Lenses on the Turret The lenses should be placed with the 25mm lens (the normal lens) in the center position (as pictured here). This prevents the telephoto and the wide angle lens from being mounted adjacently, which will cause the simple problem of the telephoto lens being visible in the corner of the frame when you shoot with the wide angle lens.
	What NOT to see in the viewfinder!

Depth-of-Field indication The lenses for the Bolex have a built-in depth-of-field indicator, in the form of a series of orange dots that appear as the lens is closed down. A typical way to utilize this is to set the lens with infinity at the far dot, giving you a depth-of-field from x-distance to infinity (x-distance being the distance of the furthest dot on the other side). If you are using the dots to determine depth-of-field, be careful that you don’t forget to re-check them when you change f-stops!

The material on these pages may be printed out for personal use only. Use as course handouts only with proper acknowledgment of authorship and the New School's Film Production Department. [Bolex Main Page] [Joel Schlemowitz Film ProductionPages] [Joel Schlemowitz Homepage] [New School Film Production] © 1999 Joel Schlemowitz All Rights Reserved