Shutter size standards

[swmcl]

Hello all,

I'd like to ask how shutter iris sizing came about. The Copal 0 size has an iris opening of around 452mm2, Copal 1 - 706mm2 and Copal 3 - 1590mm2.

What's the relationship between the sizes? It is the sqrt 2 for example...

Is it a artefact of the Japanese copying a German design that adapted a French baguette or something?

Here in Aus we have a rail (train) network where the gauge is so because that's how wide the cart wheels were ... !! I think its the same in the US. So many things are so because they are just copies of older designs rather than having a specific physical design problem to solve.

Cheers,

Steve

[John Schneider]

...Here in Aus we have a rail (train) network where the gauge is so because that's how wide the cart wheels were ...

I can't answer your question but I can add http://www.straightdope.com/columns/...n-chariot-ruts

[swmcl]

I'll admit I wasn't thinking of actually researching the issue of wheel ruts!

A very enjoyable website for sure.

[Peter K]

Steve, the thread sizes and so the shutter sizes where invented in the Twenties of the last century by Msgr. Deckel, the maker of the "Compur" and Compound" shutters. Later Copal made shutters for LF-lenses with the same sizes. Up to now but only in the sizes #0, #1, and #3.

If the diameter of the diaphragm projected in the entrance pupil of the lens is changed - not the mechanical diameter (!) - e. g. from f/5.6 to f/8, sqrt 2, the luminous flux is reduced by the factor 2.

Have fun
Peter

[swmcl]

Thanks Peter,

I did have a small thought that it might have something to do with Mr Deckel.

I'm sorry the last paragraph has me absolutely lost. However, I assume the sizes were actually meant to achieve a ratio of some sort.

I wonder if the 'ratio' were extended what the iris diameters would be ...

Do the Compound #5 and Ilex #5 fall into this ratio too? They surely can't because they are only slightly different in size ...

I need to learn some optical theory I think. Sometimes you guys just completely flatten me with your knowledge.

Rgds,

[Peter K]

I'm sorry the last paragraph has me absolutely lost. However, I assume the sizes were actually meant to achieve a ratio of some sort.

Sorry my fault

To find the diameter of the entrance pupil open the diaphragm fully. Now you can measure its diameter as it appears through the front lens with a transparent ruler placed on the filter thread. The ration between the focal-lenght of the lens and this diameter is the f-number. E. g. 300mm (focal-lenght) / 53.6mm (diameter of the entrance pupil) = f/5.6.

For the same lens but with a longer focal lenght, lets say 360mm, the diameter of the entrance pupil is 64.3mm so one needs a larger diaphragm diameter resp. shutter diameter too. Instead of the shutter size #3 a shutter size #4. And with a 420mm a shutter size #5.

Peter

[Ole Tjugen]

Shutter sizes only gradually became standardised. From around 1930 F. Deckel started reducing the available sizes, forcing lens makers to fit cells in either os the delivered sizes. Schneider and Voigtländer seem to have been using only these sizes right from the beginning, so even very early shuttered lenses from these makers have a very good chance of fitting directly into a modern equivalent.

While the selection of shutter sizes became more limited, that does not at all mean that the "modern" set of 0, 1, 3 was all there was...

There was 00, 0, 01, 1, several versions of 2, and various "tube" versions of 3, 4 and 5. For more details on 2,3,4 and 5, see the thread linked to in my signature - the post linked to deals with Compound 3, 4 and 5; Compur 2 is described in a different post in the same thread.

[Peter K]

Shutter sizes only gradually became standardised. From around 1930 F. Deckel started reducing the available sizes, forcing lens makers to fit cells in either os the delivered sizes.

I don't think Deckel would force his customers to anything. There where other shutter makers also like Gauthier/Prontor, Rulex etc. But 1930 was the time of the great depression so every factory has lost sales. So cost reduction was the reason.

On the other hand Compur made special shutters for every camera maker, also LF like Linhof, Sinar, and Graflex.

[Ole Tjugen]

Bad choise of word, perhaps. But I do notice that before about 1930, only Schneider and Voigtländer 150mm f:4.5 lenses will fit in a modern #1 shutter, while Zeiss, Rodenstock, Meyer and others only very rarely will. After about 1932, they are ALL in "standard #1 shutters". Simplifying the production line is the most likely reason for the standardisation.

There are "special" shutters much later than this too, with shorter tubes for WA lenses or special facings for special lenses. But the greatest reduction in "incompatible sizes" seem to have happened at about the time of the great depression.

[Ernest Purdum]

It seems appropriate to mention that the "size" numbers mean different dimensions for different makers. An Ilex #5 is not the same as a Wollensak #5 and both are smaller than a #5 made by Deckel.

Peter K. I suppose it has to do with my not being familiar with German abbreviations. I know that there are lots of Catholics in Munich, but am surprised to find Friedrich Deckel apparently among the Monsignori. O.K., I know that's Italian.