12x16.5 cm same as halfplate?

Jerevan · Jan 21, 2007

Am I correct in assuming 12x16.5 cm is the same thing as the halfplate size, which has the same external size as 5x7 and 13x18? Since I've already made at least one mistake regarding inches and metrical sizes, I'll ask this time around...

Roger Hicks · Jan 22, 2007

Jerevan said:
Am I correct in assuming 12x16.5 cm is the same thing as the halfplate size, which has the same external size as 5x7 and 13x18? Since I've already made at least one mistake regarding inches and metrical sizes, I'll ask this time around...

Half-plate = 4.75 x 6.5 inches = 121 x 165mm rounded to whole numbers. Allowing for the normal precision with which film sizes are given, especially by some Americans ('3x4 inch' for 3.25 x 4.25 inch quarter-plate), yes, you're right. I'm pretty sure that my one half-plate holder is marked 12,1 x 16,5 cm. The millimetre ain't gonna make much difference...

Incidentally, half-plate ISN'T half of whole-plate (6.5 x 8.5 inches) -- it's half an inch (12.7mm) bigger on the short dimension -- but quarter-plate IS a quarter of whole-plate.

Cheers,

R.

Jerevan · Jan 22, 2007

Roger Hicks said:
Half-plate = 4.75 x 6.5 inches = 121 x 165mm rounded to whole numbers.

Thank you - in my research last night I also found there was something called "halfplate" during the first half of the 19th century, which had different dimensions (4.5" x 5.5"). The overall "logic" to the system makes me sometimes laugh, at other times sigh loudly. But given the ease with which one can cut a plate of tin or glass, it's no wonder...

Justin Cormack · Jan 22, 2007

Fuji quotes it as 118x163mm (they sell half plate Acros, just got some).

Ole · Jan 22, 2007

Justin Cormack said:
Fuji quotes it as 118x163mm (they sell half plate Acros, just got some).

That makes sense. Film sizes are always a few mm smaller each way than the glass plate sizes; this is done on purpose. It was originally done to accomodate the film adapter sheaths necessary to use sheet film in plate holders, and was never changed. That's why 13x18cm film measures quite exactly 5x7 inches (127x178mm), and 5x7" film is a few mm smaller...

The same strange "half-size" phenomenon is found in metric sizes too, BTW. 4.5x6cm is one quarter of 9x12cm which is one quarter of 18x24cm, and 6.5x9cm is one quarter of 13x18cm. But 9x12cm is not half a 13x18; and nothing whatsoever is half or quarter of 24x30cm. There was also a 10x15cm size which could possibly be said to be one eighth of 30x40cm, but neither of the two fit in with the other standard sizes in any logical way.

Jerevan · Jan 22, 2007

Justin Cormack said:
Fuji quotes it as 118x163mm (they sell half plate Acros, just got some).

I looked at it, but I wasn't sure it'd fit my holders I won (purely by accident, honest!) on an auction site. Figured 18x24 film or paper would be possible to cut into two nice parts, so I'll start with some Agfa MCP I got in the closet.

clay · Jan 22, 2007

I hate seeing posts by annoying pedants. But since no one else will volunteer, i guess it is my turn to be one.

<Pedantical trivia-on>
I was surprised to find out recently that there was some difference in opinion between the French and the English over the appropriate dimensions of whole and half plates.

Apparently, Desire Van Monckhoven in 1863 determined that the proper dimensions of whole plate was 7-1/8" x 9-7/16" and half plate should be 5-3/8" x 7-1/8".

This is from "Traite general de photographie", 3rd edition, 1863 by way of Primitive Photography, the excellent calotype manual by Alan Greene.

</pendantical trivia-off>

alexphoto · Jan 23, 2007

Hi Justin
Where did you get your half plate Acros from?
Alex

Jerevan · Jan 23, 2007

I'm not Justin, but anyway, here goes: Dead Link Removed

roy · Jan 23, 2007

Interesting Justin, who was your source of supply ?
Does the film fit into a half-plate film holder ? I ask this because I once bought some and the dimensions were cut to half-plate and were a couple of mm too large.

Justin Cormack · Jan 23, 2007

Yes I got mine from Unicircuits.

I dont have a half plate film holder though (yet), only a plate holder, so I am sticking it to glass so tolerance is not so crucial. I think its the same size as the half plate film retrophotographic sell too, but I will have to check.

Richard Kelham · Jan 31, 2007

clay said:
I was surprised to find out recently that there was some difference in opinion between the French and the English over the appropriate dimensions of whole and half plates.

There is always some difference of opinion between the French and the English!

Richard

Jim Jones · Jan 31, 2007

From the 1944 ANSI centimeter photographic dry plate specifications:
12 x 16.5mm +/- .5mm

From the 1951 ANSI inch size photographic dry plate specifications:
4.25 x 6.5 +/- 1/64 (10.75 x 16.27cm +/- .4)
4.75 x 6.5 +/- 1/64 (11.91 x 16.27cm +/- .4)

Ole · Jan 31, 2007

Jim Jones said:
From the 1944 ANSI centimeter photographic dry plate specifications:
12 x 16.5mm +/- .5mm

Ye gods - that's smaller than a digisensor!

12x16.5 cm same as halfplate?

Jerevan

Roger Hicks

Jerevan

Justin Cormack

Ole

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Jerevan

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12x16.5 cm same as halfplate?

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