Re: Different Formats for Different Countries -- Variable Density

Tony Clarke wrote:
> "David Nebenzahl"  wrote
> 
> 
>>"Metric sizes" are film sizes normally stated in, well, metric measures,
>>like 6x9 and 9x12 (both in centimeters), as opposed to "inch"-sized
>>films, like 4x5, 5x7, 8x10, etc. So, counterintuitively, 9x12 film is
>>smaller than 4x5 film.
> 
> 
>     Except metric film sizes aren't exactly what they say they are. The
> frame size of a 120 film tends to be not 6cm wide but about 5.8 cm, with
120
> film being about 62mm across.

That not quite correct.
With 120 film, the film is actualy 60mm wide and the paper backing is 
62mm wide.

> The other variations likwise are a bit smaller
> than the nominal size. It allows a bit of masking in the film holder of
the
> enlarger, but nevertheless is not as precise as metricists might like
you to
> believe.

With 120 film, most cameras have film rails that are about 1mm wide.
This results in a negative where the exposed Area is about 58mm tall.

> I could claim that the pinhole camera I'm currently ba****ng from a
> Kodak Brownie 2A is a "6x12" because it works by winding through
alternate
> frame numbers down the middle of the film (where the 6x6 numbers go) but
the
> actual image size is 54 x 108mm, being the old Kodak 116 film gate with
a
> strip of brass soldered each side to provide edge sup****t for the
slightly
> smaller 120 film. It'll be printed using a 5 x 4 imperial enlarger
(DeVere
> 54) with a black card mask over the neg gl***** to minimise Callier
flare
> from the edges.
> 
>     Of course 9 x 12 is smaller than 4 x 5! Those of us used to dealing
in
> metric know that 4 x 5 is 10 x 12.5cm - are at least it should be: if
that's
> the sheet film size then image size will be smaller because of the
little
> edge-retains in the film holder.

Sometimes the conversion from Imperial measures to Metric isn't very
exact.
1 inch equals 25.4mm, so 4 inches actualy equals 100.16mm
4"x5" is actualy 100.16mm x 126mm (10.02cm x 12.6cm).
The film rails probably take up about 2mm on each edge.
This makes the actual negative about 96.16mm x 122mm (96.2cm x 12.2cm) 
on a sheet of 4x5 film.

>     Someone on a forum - possibly not this one - confused me recently by
> saying that "full plate" was 8 x 6 inches and all else was a division of
> that. Sounds like the confusion over book binding classifications based
on a
> broadsheet being 15" x 20" except when it wasn't. I thought "full plate"
was
> 10 x 8 inches, as the original master size for photos and respected to
this
> day in paper sizes. Am I wrong?
> 
>     Tony Clarke

I think that would depend on which county you were asking for a "full 
plate" in.
 From memory, the UK usualy has smaller sizes and continental Europeam 
countries tends to have longer or taller formats (depending on which 
country).
In Australia, we seem to have tended to go with the USA on film sizes 
and photographic paper.
Here a "full" plate would be 8x10 inches.