a little slip of a thing …

Diaphragm of J H Dallmeyer Air Ministry lens 14A/780 f/2.9 8 inch F.L. Some say it covers a 5×7 plate, others an 8×10 plate.

Toronto. … said my mother in describing a skinny young girl. She could just as easily have been describing a Waterhouse stop, or a leaf in a photographic iris diaphragm. In fact, have you ever wondered when and who invented this amazing aperture control?

Rudolf Kingslake in his 1989 book, “A History of the Photographic Lens” (I have copy) says, ‘In the days of the daguerreotype, obviously no means for reducing the lens aperture was required, as photographers needed all the light they could get.’. He goes on to say, ‘The commonest means for aperture control is the familiar iris diaphragm. It is not known who invented this extremely ingenious mechanism, but it was apparently known early in the last [19th] century.’.

Wikipedia has an excellent discussion of the iris diaphragm and how it works. The article suggests, ‘Others credit Joseph Nicéphore Niépce for this device, around 1820. Mr. J. H. Brown, a member of the Royal Microscopical Society, appears to have invented a popular improved iris diaphragm by 1867.’.

These articles and points all relate to glass plate and film cameras of the last two centuries.

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