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I have heard or read recently (but can't remember where - sorry) that the whole-plate glass size - 6.5" by 8.5" - was the standard size for glass panes used by Victorian glaziers in factories etc. Is there any truth in this? Googling doesn't seem to produce any clear answers.
Thank you,
Charles

Happy New Year Charles.

I suggest you contact the RPS: http://www.rps.org/

Alternately you might like to contact the Worshipful Company of Glaziers and Painters of Glass, whose contact details are available at: http://www.worshipfulglaziers.com/contact_us-14.htm

Steve

Thats exactly what I read yesterday Charles......coincidence.

Hello Tony,
Ah good. Where, pray I, did you read that?
Thanks,
Charles

Blimey good question.....as I switch between several books at once and tend not to read one all the way through?

So after a quick flick through I found it in Victorian Photographers at Work by John Hannavy.
Page 22 accompanying an image.

" Plate sizes: this image is described as sixth plate size. Sizes were based on fractions of Victorian glass plate, which measured 6.6 by 8.5 inches (16.5 by 21.5 cm), as used in windows, and were used to describe all small images, including dageurreotypes, despite the fact they were not made on glass. To keep proportions the same, half plate was a little more than half of the sheet, but quarter plate was a genuine quarter. Other popular sizes were ninth and sixteenth."

Your may well of read it yourself as it was one of the books I leant you....

Thanks Tony. I knew I had seen it somewhere recently.
Charles

Hi Charles,

Your question about plate sizes remined me that I had read something a while ago, but approaches it from another direction.

The design of any lens is dominated by what is known as the Petzval Sum, which is related to the curvature of the image of a flat object. Until the mid 1880’s nearly every lens made overcame this curvature by overcorrecting the astigmatism of the lens. It was a trade off between the two.

As lens design went in the 1830’s, as long as the apertures were low – about f/15 - the astigmatism was not too noticable, as long as the field of view was limited to about 20 deg from the lens axis. When Chavalier designed the lens for Daguerre, a focal length of 15” was chosen. With a 20 deg limit either side of the axis, this gave a plate size of 16cm x 22cm which when ronded off is about 6-1/2” x 8-1/2”.

Susie