What is the difference between DPI and PPI?

Dots Per Inch (DPI) refers to the number of dots of ink used per inch to create an image on a physical page. Pixels Per Inch (PPI) refers to the number of pixels it takes to create a digital image.

PPI settings in a digital photo will not noticeably change the digital quality of that photo until you expand the dimensions of that image beyond it's original intention. For example, leaves on a tree or reeds in a pond will lose some distinction if you take a 4x6 image and expand its dimensions to an 8x10. In these cases, reproductions lose a bit of clarity because you are asking the image to use the same number of pixels to fill a much bigger space, resulting in a lower quality output.

The 600 dpi photo appears sharper than the photo scanned at 300 dpi.

Why a higher resolutiion?

Digital images with higher resolution settings can produce more detailed photographic prints. Scanning at a higher DPI or PPI will give you and your family more options for reprints and copies to be passed around for generations to come. They will look great in photo books, calendars, and holiday cards, too. If you are scanning and would like to make enlargement prints from your digital files, we would recommend having them scanned at 600 dpi.

What will the dimensions be?

If you have a 3x5 print and you want to enlarge it to a 5x7 you would need to scan it at a higher DPI than 300 dpi. Otherwise, when you go to enlarge it, you won't maintain the 300 dpi needed for photo quality. Here's why:

At 300 dpi a 3x5 picture measures 900x1500 pixels. However, a 5x7 at 300 dpi is 1500x2100 pixels. So, unless you add more pixels to the scan, you aren't going to have enough to enlarge the 3x5 to a 5x7 and still maintain the 300 dpi resolution.

The pixels of the image vary depending on the mega pixels of the camera that took the photo. A photo that was taken with a 3.5 mega pixel camera will have smaller pixels than a photo taken with an 8.0 mega pixel camera.

Here are some averages to give you a better idea of the dimensions.

4 x 6300 dpi1200 x 1800 Pixels
4 x 6600 dpi2400 x 3600 pixels
5 x 7300 dpi1500 x 2100 pixels
5 x 7600 dpi3000 x 4200 pixels

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