Lac des Escarcets, panoramic landscapeWith digital photography, some are a little bit confused with images sizes in dpi, ppi, pixels or inches (or cm).
First, in my mind the only real unit for digital image size is the pixel.
Second, dpi and ppi are same things : dpi is for dots per inch and ppi is for pixels per inch.
Printing at 300 dpi means you will use 300 image's pixel to print one inch of paper.
So if you want to print a photo at 300 dpi on a 10 inches wide paper your photo must be 3000 pixels wide (10x300=3000).
The original file for the picture above has 7155x2385 pixels. If i print it at 300 dpi i'll have a print of 23.85x7.95 inches or 60.58x20.19 cm. If i print it at 200 dpi i'll have a print of 35.78x11.93 inches or 90.87x30.29 cm.
If someone tells you I want your images at 300 dpi, it's incomplete. He must tell you the needed print size (in inches or cm).
During the last years, most of the DSLRs gave 6 Mega Pixels images : 2000x3000 pixels.
At 300 dpi, this image can be printed on a 16.93x25.4 cm page.
If a magazine wants to print it on a full 20x30 cm page, he has to solutions.
- printing at 254 dpi instead of 300 dpi.
- increasing the file size by software to obtain a 3543x2362 pixels image.
