I have all of my prints for sale printed photographically, I can make 30x40 prints from a file with 92 dpi that are as good as any I had made from my 6x7 negs, but I know my printers need a much higher res. than that if scanning from a neg.
Terry L. Mair Mair's Photography 158 South 580 East Midway, Utah 84049 435-654-3607 www.mairsphotography.com
----- Original Message ----- From: "karl shah-jenner" <shahjen@xxxxxxxxxxxx>
To: "List for Photo/Imaging Educators - Professionals - Students" <photoforum@xxxxxxxxxxxxxxxxxxxxxx>
Sent: Sunday, February 27, 2005 5:40 PM
Subject: Re: -Gallery X - (and a new question at the bottom)
: Now, this brings me to a new question. (The first of more to come now I have my brand new XP.) Earlier, Emily said I should not scan photos at 'more' than 800 dpi. My question is: : : How low (dpi) can I scan in the photos and still get a good print?
you have to think FIRST of what size you want the prints to be, assuming a print resolution of 300 pixels per inch (ppi)
then multiply 300x the size you want to tell you how many pixels you need to start with
so 5x7 = 1500 x 2100
8x10 = 2400x3000
16x20= 4800 x 6000
now we head to the scanner..
forgive me but I've not followed the thread so I'm not sure what format you've used so I'll assume 35mm which is 24mm (call it an inch) x 36mm (1 1/2")
so for the 5x7 you need to scan at 1500 dpi (really ppi) the 8x10 needs 2400 dpi (2500 to be precise*) the 16x20 = 4800 dpi (5000 precisely)
*assumption of 1" for 24mm is just a guide - 25/24 = 1.041667
if you'd shot with 6x6 then you would need to scan at the following resolutions:
5x7 = 666ppi 8x10 = 1067ppi 16x20= 2133ppi
you can always scan at HALF these resolutions then upsize using a GOOD algorithym (use irfanview) but you'd actually be sticking in interpolated data that wasn't in the original shot.
karl
