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Copal, Compur, Prontor, Ilex and Compound Shutters.

If you're hunting for a lens to fit your large format camera, you have likely come across this topic.

Your desired optic comes mounted into one of the shutters mentioned above, but what diameter of hole will you need to mount it onto a lens board?

I have put together a reference guide to help you.

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Identification

Most shutters have the model or manufacturer printed or engraved into the shutter somewhere - usually on the front face or outer edge of the shutter.


There are five common brands of leaf shutters from over the years that you will find mounted between the glass of many large and medium format lenses. They are Copal, Compur, Prontor, Ilex and Compound.

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Determining the required diameter.

The manufacturers produced different sized shutters depending on the size of the lens being used. They are usually numbered sizes of 0 to 3, with 0 being the smallest and 3 being the largest. Ilex and Compound shutters begin at 3 and increase in size to 5.


Each type and size of shutter will need a different diameter of mounting hole for a lens board. The lens mounts to the board, and the board attaches to the camera.


Some sizes are the same between brands (As an example, Copal 1 and Compur 1 shutters require the same diameter hole at 41.6mm).

List of Shutter Sizes and Diameters

Here are the diameters of hole you will need to make into a lens board to mount a respective shutter. Of course, this is not an exhaustive list - and many shutters have been made, modified or adapted over the years. If you're in any doubt, measure yours carefully.

Copal

  • Copal 0 34.6mm
  • Copal 1 41.6mm
  • Copal 3 65mm
  • Copal 3s 64.5mm

Compur

  • Compur 00 26.3mm
  • Compur 0 34.6mm
  • Compur 1 41.6mm
  • Compur 2 52.5mm
  • Compur 3 65mm

Prontor

  • Prontor 0 34.6mm
  • Prontor 1 41.6mm
  • Prontor 3 65mm

Prontor Pro

  • Prontor Pro 0 34.6mm
  • Prontor Pro 1 41.6mm
  • Prontor Pro 3 65mm

Ilex

  • Ilex 3 50.42mm
  • Ilex 4 66.14mm
  • Ilex 5 85.47mm

Compound

  • Compound 3 ~60mm
  • Compound 4-X 9 ~65mm
  • Compound 4-X 10/11 ~76.7mm
  • Compound 5-X 12/I/II ~90mm
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Mounting a large format lens onto a board.

Your lens should come with a retaining ring of the correct size for your shutter. Unscrew the rear cell, remove the retaining ring and watch out for any shims or washers.

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Mount the rear of the lens through the board and install the retaining ring. You may need to use a tool to torque it down tightly, but in most cases fingertight is enough.

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Reinstall the rear cells

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And there you have it - a mounted lens on a board ready to be used.

Well, actually...

If you've spotted something not quite right in this article, feel free to drop me a message.

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