Why Copal #00, #0, #1, #3? A quantitative answer.

[jetrink]

So, like many people have, I found myself wondering about this weird set of sizes. Most of all, why the gap between #1 and #3? I read through all of the threads I could find on this forum, but I couldn't find a complete answer for why they were numbered this way. Most answers were of a vague or historical nature. #00 reminded me of wire gauges and how they are mathematically related to the diameter of the wire, so I plotted the diameters of the shutters in Excel (re-designating #00 as -1) and it all became clear:



If you take the Copal number of a lens, C, its characteristic diameter in mm is equal to 24 + C * 6. As for the gap, Copal #2 does exist in a sense, there were just no lenses made in that size because it was easy enough to jump up to a #3 if #1 was too small.

[lassethomas]

If you take the Copal number of a lens, C, its characteristic diameter in mm is equal to 24 + C * 6. As for the gap, Copal #2 does exist in a sense, there were just no lenses made in that size because it was easy enough to jump up to a #3 if #1 was too small.

But there were lenses made for the #2. The infamous Xenotar 150/2,8, the Angulon 165/6.8, the Symmar 240/5.6 and a few more. But there are different versions of the #2 shutters with different threads. I'm no expert and it's rather confusing.

[jetrink]

But there were lenses made for the #2. The infamous Xenotar 150/2,8, the Angulon 165/6.8, the Symmar 240/5.6 and a few more. But there are different versions of the #2 shutters with different threads. I'm no expert and it's rather confusing.

Oh, thanks for the correction. People always seem to omit #2 from lists and tables so I just assumed it didn't exist.

[Oren Grad]

IIRC Copal indeed never offered a #2. There are various Compurs referred to as #2, also an Ilex Acme #2, maybe others - I hope one of our experts on classic lenses/shutters can weigh in.

[BrianShaw]

... maybe others - I hope one of our experts on classic lenses/shutters can weigh in.

Graphex/Rapax also had a #2 size, in addition to a 1 and 3.

[Mark Sampson]

I have at least one lens in a Kodak Supermatic #2 shutter.
If you look at catalogs from pre-WWII, you'll see that lens makers often gave numbers to lenses in a series, as in "Dallmeyer #2" and many similar, rather than listing them by focal length, which became normal practice later.
It's probable that labeling shutters by number worked the same way, and were never meant to express compatibility between brands. For example, look at the size difference between an Ilex Acme #3 and a Copal #3. Compatibility came later, when there were few makers left.

"The great thing about standards is that there are so many of them."

[Tin Can]

Add Copal S.

[Oren Grad]

If you look at catalogs from pre-WWII, you'll see that lens makers often gave numbers to lenses in a series, as in "Dallmeyer #2" and many similar, rather than listing them by focal length, which became normal practice later.
It's probable that labeling shutters by number worked the same way, and were never meant to express compatibility between brands. For example, look at the size difference between an Ilex Acme #3 and a Copal #3. Compatibility came later, when there were few makers left.

Right. The standardization of specifications for 0/1/3 shutters is really just a Copal and late-model Compur/Prontor thing, no?

[Tin Can]

and none of those tiny shutters can work on old large lenses

There were bigger shutters made, but all I have found was old big junk

I like to shoot lenses with far larger diameter

and only Packards can do it

an example is the 405 KODAK Soft Focus here in a mirror selfie

web Mirror Selfie by TIN CAN COLLEGE, on Flickr

Linhof triple Kodak 405 Portrait by TIN CAN COLLEGE, on Flickr

[Daniel Unkefer]

Smaller shutters offered faster speeds than bigger shutters in some cases. Remember people were hand holding 8x10 Technikas, shooting wide open in the old Schneider ads. So they were perfectly useable wide open