scanning negatives - resolution

i would like to scan all my negatives to have digital copy of all my photos.
when I came to lab I asked them to scan them in 2400 dpi. i sure sounded
like an idiot, because they obviously scan only in 300 dpi :-) but my point
is, 25x36 (cm) in 300 dpi equals 9.84x 14.17 inch and that is 2952 x 4251
pixels. if I want to scan negative in this resolution it actually is 4251 /
1.41in (36mm) eq 3014 dpi. this ~ 3000 dpi is actually an optical resolution
of the scanner. so it is a really different if you scan at 1200, 2400 or
3000 dpi. is that so the scanner always use same optical resolution and the
result is sized by the software? am I completely wrong? can someone bring
more light here?
thank you

freightcar wrote:
i would like to scan all my negatives to have digital copy of all my photos.
when I came to lab I asked them to scan them in 2400 dpi. i sure sounded
like an idiot, because they obviously scan only in 300 dpi :-) but my point
is, 25x36 (cm) in 300 dpi equals 9.84x 14.17 inch and that is 2952 x 4251
pixels. if I want to scan negative in this resolution it actually is 4251 /
1.41in (36mm) eq 3014 dpi. this ~ 3000 dpi is actually an optical resolution
of the scanner. so it is a really different if you scan at 1200, 2400 or
3000 dpi. is that so the scanner always use same optical resolution and the
result is sized by the software? am I completely wrong? can someone bring
more light here?
thank you


Scanning negatives at 300 dpi isn't good enough. Find another lab.

The confusion here is DPI. It is better to work in pixel's dimensions. First
you must know the maximum optical scanning DPI or PPI is more precise. Let
assume 4000 PPI and this is known as max input PPI. Your source is 35mm
negative so for full frame scan is 24x36mm (1x1.5 inches). Apply max input
PPI will give you 1 x 4000 and 1.5 x 4000 = 4000 x 6000 PPI (pixel's
dimensions). Now come to image output PPI and 300 is more than sufficient
for printing. So 4000/300 PPI and 6000/300 PPI will give you print size
13.33 x 20 inches. Remember don't confuse image input and output PPI also
don't confuse image output PPI and printing output DPI. Your lab probably
give you image output PPI 300 which is correct.

"freightcar" . wrote in message
. ..
i would like to scan all my negatives to have digital copy of all my
photos. when I came to lab I asked them to scan them in 2400 dpi. i sure
sounded like an idiot, because they obviously scan only in 300 dpi :-) but
my point is, 25x36 (cm) in 300 dpi equals 9.84x 14.17 inch and that is
2952 x 4251 pixels. if I want to scan negative in this resolution it
actually is 4251 / 1.41in (36mm) eq 3014 dpi. this ~ 3000 dpi is actually
an optical resolution of the scanner. so it is a really different if you
scan at 1200, 2400 or 3000 dpi. is that so the scanner always use same
optical resolution and the result is sized by the software? am I completely
wrong? can someone bring more light here?
thank you