Why dpi is Important when Printing Your Photos
on a Color Printer

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3.  Does your Photo have enough Pixels of Resolution to fulfill your Printing Requirement?

For our example, we want our photo to fill a 6" x 4" rectangle on the page and we want a good quality print of 300 dpi.

If you divide the 6" x 4" rectangle up into one inch squares, it will have 6 squares across horizontally and 4 squares vertically and each one of these square will be filled with 300 dots of ink horizontally and 300 dots of ink vertically when the photo is printed.  So, the total number of printed dots in the 6" x 4" rectangle will be:

6" Horizontally:  6 squares x 300 dots = 1800 printed dots.  So 1800 pixels will be required horizontally in the photo.
4" Vertically:  4 squares x 300 dots  = 1200 printed dots. So 1200 pixels will be required vertically in the photo.

So, we need a digital photograph that is made up of 1800 pixels horizontally and 1200 pixels vertically.
The photo can have more pixels than this, but to meet our print quality goal, it must have at least this many pixels.

To take this kind of picture, our digital camera will have to be rated at least 2.16 megapixels because
1800 pixels x 1200 pixels = 2,160,000 pixels = 2.16 megapixels

To quickly recap:

1. Decide on the printout size (rectangle or square) that you want the photo to have on your page.
2. Decide on the dpi print quality that you want the photo to have when printed.
3. Figure how many pixels should be in your digital photograph to meet these printing requirements.
   (Inches x dpi = pixels of resolution)

• See Digital Photo Quality and Resolution to learn about megapixels and setting your digital camera to take high resolution photos,

What Are Your Options If You Don't Have Enough Pixels?

You might be wondering what options if you might have if your photo does not contain enough pixels to meet your printing requirements.  Here are some suggestions:

1. Use a smaller print out size for your photo.  If you picked a 6" x 4" printout square, could you settle for a 4½" x 3" rectangle instead?  This would be a rectangle that is 75% the size of the original.
   
   NOTE: You should keep the proportions of the photo the same.  If you decrease the length to 75%, then you should also decrease the width to 75%, so you don't distort the image in the photo.
   
   For instance, 75% of  a 6" x 4" rectangle is:
   0.75 times 6" = 4½"
   0.75 times 4" = 3"
2. Go with a lesser print quality.  Instead of 300 dpi, settle for 250 or 200 dpi.  Once you see the printout, then you can decide if the photo still looks OK.
3. Retake the photograph at a higher resolution.  If your digital camera is an inexpensive point-and-shoot model that doesn't have a high resolution, then maybe you need to consider getting another camera with a higher megapixel rating.

• See Common Digital File Types for information on which digital file types use NO compression so will not lose any image quality when a photograph is saved to the camera's memory card.

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