Scanning film negatives - Resolution, DPI and file size [duplicate]

Question

I use a Epson V800 scanner to scan my 35mm film negatives. I've set the resolution on the software (silverfast 8) to 3200dpi and the result was a tif file with 4500x3000px and 15mb.

If i select that image and then go to properties -> details, Windows tells me that the image has a resolution of 360ppi (i assume that is the same of dpi).

If anyone can help me, i have 3 questions,

1 - I've scanning at 3200dpi, why my finale image is only 360dpi/ppi?

2 - At 3200dpi the resolution is 4500x3000px ?

3 - For the resolution of 4500x3000 what is the maximum print size?

Thanks for the help.

Ricardo

Answer 1

dpi is about the inches... pixels per inch.

4500x3000 pixels at 3200 dpi is 1.4 x 0.94 inches, on the film.

4500x3000 pixels at 360 dpi is 12.5 x 8.33 inches, on the print paper. The spacing and size of the printed pixels. It should have shown the inch dimensions too.

This is simple division.... 4500 pixels / 360 dpi = 12.5 inches.

Exactly the same pixels, but simply scaled to different inch sizes on film or paper media. This is an extremely important basic principle of printing. Dpi is just a number that does not even exist until the inches are declared.

For 4500x3000 pixels, the print size depends on the dpi printed... If for dramatic example, at 100 dpi would be 45x30 inches. If printed at 300 dpi, then 15 x 10 inches. If printed scaled to 12x8 inches even, then 375 dpi.