Here is a great question from a #Cazillion on DPI. In my video I explain how it works and why DPI/PPI really don't matter when exporting your images.
Subject: resolution/printing
To: Gregory Cazillo
Hey Greg, I am new to printing and I am having a problem regarding resolution/printing. Some of my pics say x and y resolution 72 dpi and a pic taken minutes later will say 300 dpi.(I am getting this from the exif info in flickr). Also, at this time i have only edited in iphoto.
1. How do I set my resolution for the best possible quality?
2. How does dpi relate to printing size and quality?
3. How/Can I print large prints ex. 20x30 with my D90
Thanks for all your help....
Definitions from Wikipedia:
PPI: Pixels per inch (PPI) or pixel density is a measurement of the resolution of devices in various contexts; typically computer displays, image scanners, and digital camera image sensors.
DPI: DPI is used to describe the resolution number of dots per inch in a digital print and the printing resolution of a hard copy print dot gain; the increase in the size of the halftone dots during printing. This is caused by the spreading of ink on the surface of the media.
Comments
I have a D5000 with a 12MP sensor which produces 4288pixel images (on the long edge). Doing the math I could print a 14" image at 300dpi natively. Or I could print a 20" image at 214dpi natively (no up-rezing). However if I wanted to print the 20" image at 300dpi I would have to up-res from 4288 to 6000 pixels. Am I understanding that correctly?
Just to review: don't worry about your DPI or PPI!
I want to see your 40 X 60 from a 2MP camera!!!! Then I will believe it!!!!PLEASE SHOW EXAMPLES!!! Man I believed in you untill this!!!!
Megapixels
Resolution
common print size (rougly 300dpi)
2 MP
1600x1200
10x13cm / 4x6"
3 MP
2048x1536
13x18cm / 5x7"
4 MP
2400 x 1600
18x23cm / 6x8"
6 MP
3000x2000
20x30cm / 7x10"
8 MP
3600x2400
30x40cm / 10x14"
12 MP - better more
4200x2800
40x60cm / 16x24"