Overview of All Hole Diameters for Large Format Lens Boards (Compur, Copal & Compound)

What are lens boards?

Lens boards are used in large format photography to attach the lens together with its shutter to the camera.

Different camera systems use different lens boards, which vary in both size and shape.

We currently offer lens boards in five different versions (sorted by size):

1. 80 x 80 mm lens boards for Horseman 45FA, 45HD, VH
2. 92,5 x 94 mm lens boards for Graflex Crown & Speed Graphic
3. 96 x 99 mm lens boards for Linhof, Technika, Ebony, Tachihara, Wista, Shen Hao, Chamonix
4. 110 x 110 mm lens boards for Toyo Field 4x5 45A II CF A AR AII AX
5. 140 x 140 mm (effectively 139,7 mm) lens board for Sinar & Horseman View

Depending on the size and focal length of the lens used, the lens board must also have a specific hole diameter. Lens boards are usually supplied pre-drilled by the camera manufacturer. However, if no replacement lens board is available, one has to be custom made. We supply such custom made lens boards in various sizes and with different hole diameters.

The diameter of the drilled hole is commonly referred to as the “Copal number”. We offer the lens boards listed above with all common Copal, Compur and Compound hole diameters.
(Note: The maximum selectable hole size is limited by the outer dimensions of the respective lens board.)

Copal shutters

• Copal #0: 34,6 mm
• Copal #1: 41,6 mm
• Copal #3: 65,0 mm
• Copal #3S: 64,1 mm (variant of the #3 with a smaller rear thread diameter; often also stated as 64,5 mm)

Worth noting: there is no “Copal #2”. Nidec Copal skipped this size for large format lenses, going straight from #1 to #3. This sometimes confuses beginners, but it is correct.

Compur shutters (historical sizes)

• Compur #00: 26,3 mm
• Compur #0: 34,6 mm
• Compur #1: 41,6 mm
• Compur #2: 52,5 mm (there were different versions of the Compur II and Compur II 5/2)
• Compur #3: 65,0 mm

Compound shutters (historical sizes)

• Compound Dagor: 38,0 mm
• Compound #3 sleeve 7: 63,2 mm
• Compound #4 sleeve 9: 69,1 mm
• Compound #4 sleeve 10: 80,0 mm
• Compound #5 sleeve 12: 93,4 mm

Note: In some cases the hole diameters for Copal and Compur are identical, e.g. for #0 (both 34,6 mm).

Recessed and blank versions

We also supply the lens boards in a “recessed” version. Here the opening is set back inwards (usually by 12 mm or 17 mm, depending on the camera system), which allows the use of particularly wide-angle lenses.

Lens boards marked “Blank” are supplied without a hole and are suitable for anyone who has an unusual lens size and wants to drill the hole themselves.

Practical tips for installation

• Anti-rotation pin: Almost all leaf shutters have a small protruding screw on the back that secures the shutter in the board against rotating. Custom-made lens boards lack the matching notch, so it must either be filed in or the screw must be removed from the shutter.
• Off-centre hole: On Linhof Technika lens boards (96 x 99 mm), the factory hole is often not exactly centred but slightly offset downwards so that the optical axis points correctly at the film. If you drill a blank board yourself, you should allow for this offset.

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How to mount a lens on a lens board

In this tutorial, David Hancock shows how to correctly mount a lens with a Copal shutter on a lens board:

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Custom-made lens boards from Ausgeknipst We make lens boards in 5 sizes with all common Copal, Compur and Compound hole diameters, also in recessed and blank versions. View all lens boards