You’ve seen them. . . prints from digicams blown up to posters. The pixels are the size of a grapefruit and it’s not pretty.

There are limits to how large you can go. Eventually experience helps you to just “know” these limits, and printer and paper quality play a part in this. But there is a rule of thumb you can use as a starting point.

To calculate (in inches) the largest photo-quality print you can make from a digital file, using its native resolution, meaning no interpolation, divide the vertical and horizontal pixel counts (see your manual) by 240.

If you are making images for commercial publication or other critical applications, or if you want exhibition-quality prints from commercial printers, divide the pixel counts by 300.

Let’s take an image from the Canon PowerShot G6 as an example. It makes a high quality jpeg image at 3072 x 2304 pixels. Using the formula above, that would generate a native print size of 12.8″ x 9.6″ at 240 DPI. Now remember, this assumes you haven’t rezzed up the image in Photoshop.

The next step in the formula is to take this print size and multiply it by 25%. That is the largest amount of image interpolation the picture can stand and still maintain reasonable photo quality – in my opinion.

In the example above, that would change the maximum print size to 16″x 12″.

Note, this is only a GUIDELINE. So don’t make a religion or cult out of my advice. Just use it to get started and do your own experimentation. I think you’ll find that this guideline is pretty accurate.

You can go bigger with some post-processing tricks and add-on software, but the results are far less predictable.

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This post sponsored by the Digital SLR Store

You may not realize it, but keeping your inkjet printer clean is very important. Dust, dirt, debris of any kind can ruin a print or series of prints. Here are some things you can do to protect your printer and your prints.

1) Turn your printer off when not in use. Typically, this “parks” the heads and caps them shut so dirt and air can’t get into the lines.

2) Cover your printer when it’s not in use. Dust from the ceiling, in the air and your workspace can get in and muck things up.

3) Use compressed air to blow out debris once per month. Be careful to keep the can upright and discharge some of air away from the printer to make sure the liquid propellant doesn’t get into the printer.

4) Run the printer’s ink cleaning or power cleaning routine after prolonged periods of non use. Even though in theory, the printer being turned off should keep problems to a minimum, users of the most sophisticated printers like the Epson photo printers, will find that air bubbles and nozzle dirt can still be a problem. While it costs you ink/money to run the cleaning utility, it’s worth it. It only takes one speck on a large art print to make it worthless.

5) Keep the work area around the printer clean and neat. Don’t set boxes, coffee cups, snacks on the printer.

These are all easy, common sense things you can do to prolong the life of your inkjet printer, improve the quality of your prints and get the most out of your investment. Got any other tips?

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This post sponsored by the Digital SLR Store