Upload & Sell: On
IF ... he is talking about a scan rate of 300 ppi for film then your numbers go something like this:
Film area = 24mm x 36mm, converted to inches @ 25.4mm/in = .9448in x 1.4173in
(24/25.4 & 36/25.4)
Scanning @300 ppi would yield an image 283 x 425 pixels as noted by WAYCOOL.
(.9448*300 & 1.417*300)
Taking the 283 x 425 pixel image and printing it @ 300 dpi (same 300/in as scanned) would yield a print size of .9448in x 1.417in the same size as the negative, i.e. a contact print.
(283/300 & 425/300)
Printing @ at the lower 150dpi would then yield a larger print of 1.9in x 2.8in as WAYCOOL points out.
(283/150 & 425/300)
Printing @ an even lower 100dpi would yield a print size of 2.83in x 4.25in
(283/100 & 425/100)
However, (as noted by others) ... IF he is talking about 300dpi for printing, then we really have no way of knowing what scan rate is being used to produce the file. Once we know the scan rate, then we can apply that number to our negative size to determine our file dimensions.
(.9448 * scan rate & 1.417 * scan rate)
After which we can divide the file diminension by our desired print dpi.
My guess is that he meant that after the print was scanned (rate unspecified), the file would then be printed @ 300dpi. Without knowing BOTH the scan rate AND the dpi being printed at, it is not really possible to know how large a print can be made (not to mention the viewing distance of the print in application) from a scan.
BIF brings out a point that a proof sheet may very well be a 300 ppi scan rate, but if the tone of the discussion was about quality (vs. convenience of a proof sheet), it would be difficult to imagine that he meant a 300 ppi scan rate, but rather a 300 dpi printing from the resultant file produced by the scan (rate unspecified).