74images wrote:
I'm Lost on This Comment?
If I want to Scan a 35mm Negative it Should Be at 600 dpi not 3200 because thee Photo will Degrade if it's Scanned at the Higher DPI? (3200)?
What DPI Should a Negative be Scanned at if I Need to Enlarge the Image Either to 5 by 7, 8 By 10, & Even Higher to 11 by 14, that information I Need to Know?
74images
Well, first of all, let's separate scanner resolution into optical and digital (interpolated). Most scanners have an optical resolution of 300 to 6400 dpi. Their drivers can interpolate files to higher resolutions, but that's just adding fake pixels made from the real ones, and scanner drivers are not very good at doing that! If you need to interpolate, use On1 Resize.
Next, let's separate scanner dpi from file PPI. Your scanner records "dots". When you tell the scanner driver software to scan "8x10 inches at 300dpi", it creates a file with 2400x3000 PIXELS, and stuffs the EXIF or TIFF file header with a resolution value of 300 dpi. The term dpi means dots per inch. In the case of a file from a scanner, it really represents the CAPTURED resolution.
The term, PPI, means how many
original, saved-by-the-scanner-or-digital-camera, pixels are going to be spread over every inch of output. Think of PPI as printer input resolution, as in "What do I need to feed my printer as a minimum to get good results?"
Labs like to work with 180 to 360 PPI, depending on print size. The larger the print being made, the LESS resolution you can get away with. If you're making an 8x10, 240 PPI is the minimum. Beyond 300 PPI, you're just wasting network bandwidth, storage space, and processing time. But a 5x7 looks better at 300 to 360 PPI. And a 24x36 looks absofreakin'lutely fantastic at 180 PPI!
DOTS have DIMENSIONS. PIXELS are just NUMBERS. Burn that into your brain with a laser!
You can make pixels any size you want, by representing them with a few or many dots! That's why PRINTERS often have very high dpi... An inkjet printer might use 2880x5760 dpi to reproduce your 24x36", 180 PPI image. A silver halide-based mini-lab might use a laser and scan at 600 dpi to reproduce your 12x18", 240 PPI image. And the result will look indistinguishable, in terms of detail, when viewed at the diagonal dimension of the print!
When calculating the file size you need to capture from a print or negative, you need to know the range of print sizes that will be made from the scan. Scan in 48-bit TIFF, if possible, at the size that will yield enough INPUT PIXELS to make the largest print you will need, at the resolution you will need to send to the printer.
For example: If I'm making 8x12 images, un-cropped, I'll scan 2400x3600 pixels (i.e.; scanning an image *to* 8"x12" @ 300 dpi using the scanner driver settings makes 2400 by 3600 pixels!). If I'm making 24x36 posters, I'll scan *to* 24"x36" @ 180 dpi, making a file with 4320x6480 pixels. Of course, it is okay to scan MORE pixels and be able to crop the image, later...