[W&B] Half-plate sizes - give or take a little . . .

[Milan Zahorcak]

Rob,

Now you see - this is why I only do early lenses.

No measuring, no confusing sizes, no math - and once you get past Petzval
Sums and things like sagittal and tangential field aberrations - no
confusing technical terms.  Well, except for maybe the occasional 'lignes'
and 'Imperial Inches.'

I don't know how you guys do it.

mz


Rob McElroy wrote:
> 
> Milan,
> 
> Even though it seems that 4¼" x 6½" would be correct for a 
> half-plate, 
> it isn't that simple, despite the fact that a full-plate is 6½" x 8½" 
> with no variation in its standard size.  Half-plates during the 
> daguerreotype / ambrotype era are more commonly 4¼" x 5½" 
> (probably due 
> to their more aesthetically pleasing ratio of length to width).  When 
> you get into the dry plate era, the term "half-plate" could refer to 
> various sizes (all of them relatively close in size), depending upon 
> what country you were in.  The English half-plate was commonly 4¾" x 
> 6½", while 4½" x 6½" was common elsewhere.  The slightly 
> smaller 4¼" x 
> 6½" we have been discussing here, is sometimes referred to as "double 
> quarter-plate" in England, to differentiate it from their 4¾" x 6½" 
> half-plate. The closest "Continental" plate size to 
> half-plate was 12cm  
> x 16cm, which is approximately (but not exactly) 4¾" x 6&5/16".
> 
> So are you confused a little?  Don't be; it's not easy to 
> figure out, as 
> there were no absolute standards.  Also, the French, German, 
> and Italian 
> dry-plate manufacturers had their own metric sizes.
> 
> By the time cut film and roll film was replacing plates, it 
> seems that 
> 4¼" became the preferred width, and the 4½" and 4¾" widths of the dry 
> plate era were essentially eliminated.  The only time the 4½" 
> dimension 
> seems to show up is on 3½" x 4½" film, with 4¾" becoming a 
> dimension of 
> the past.  Hey, that's got a nice ring to it..."Dimension of 
> the Past."  
> It sounds like a potential Twilight Zone or X-Files episode.
> 
> Probably more than anyone cared to know about film sizes.
> 
> Cheers,
> Rob McElroy
> Buffalo, NY