Printing images can throw up all kinds of problems, from blurry details or runny ink to unsightly blotches. Here’s our guide to fixing these problems and more on the Mac.

Getting the best prints from your ink-jet printer can be tricky. Most printers will warn you when ink levels are low, but other problems are tougher to pinpoint. Whether your prints suffer from pixelation or puddling, here’s a guide to recognizing and correcting the most-common print problems.

Mechanical problems

A clogged or misaligned print head won’t print at its best. Since mechanical details vary from printer to printer, you should consult your printer’s manual for specific information about solving print-head problems with your model. Here’s what to look for:

Prints are lighter than expected or contain white spots or horizontal lines.
These signs point to a clogged print head – especially if you haven’t used your printer for some time. Clean the head by running the printer’s utility program. If you can’t find it, try accessing it from Printer Setup Utility (/Applications/Utilities). Select your printer from the list, and choose Configure Printer from the Printers menu.

You may need to clean the head several times for best results. Be sure to print a test sheet between cleanings to avoid damaging the nozzles.

If the cleaning routine doesn’t work, try leaving your printer turned off overnight. The next day, run the cleaning process again. The dried ink will soften, making it easier for the printer to clean.

If you have a chronic problem with clogged heads, make a habit of turning your printer off at night. (Turn it off at the printer, not at the power strip.) In some models, doing so will engage a capping mechanism that protects the nozzles.

Most printer utilities will let you print a test sheet that uses all the printer’s ink cartridges. If you haven’t printed a colour image in a while, print a test sheet before printing a large file – it wastes less ink than a bad print.

Vertical lines are jagged.
This is usually a sign that the print head is out of alignment. There’s not much you can do to avoid this problem – all print heads become misaligned over time. Your printer utility should include an option for correcting the problem.

Colours are missing or prints lack shadows and contrast.
Colours may print inconsistently even before your printer instructs you to replace a cartridge. If the cartridges are low on ink when the problem occurs, try replacing them – this may improve colour quality.

If there’s enough ink but your print seems to be missing a particular colour, you probably have a clogged nozzle, so you’ll need to clean your print head. If your print lacks shadows and contrast, the black ink cartridge is the likely culprit.

Colour quality can also suffer if ink cartridges have been in the printer for more than six months. Try swapping in a new cartridge. If your image looks psychedelic, make sure you haven’t loaded an ink cartridge in the wrong colour slot.

Paper problems

Your printer isn’t always at fault. The wrong paper or the wrong printer-driver settings can also cause a bad print. You’ll usually get the best results – and encounter fewer problems – if you stick with your printer manufacturer’s inks and papers. But if you’re trying to be creative or save money by trying alternative media or third-party papers, the following tips should help.

Prints are blurry.
Your paper may be damp, or you may have loaded it with the wrong side facing up. Most papers have only one side designed for printing – usually the brighter or shinier side.

If you loaded the paper correctly, try using a different paper setting. Your printer may be using too much ink for the selected paper. Uncoated papers absorb more ink than coated, or glossy, papers. In the printer driver, switch to a lower-quality setting, or turn off options that use more ink – the Super MicroWeave setting in some Epson printers, for example.

Pictures are grainy.
If you’ve already cleaned and aligned your print head and your images still look as though they have old-fashioned film grain rather than smooth gradations, try switching to a higher-quality print setting. If that doesn’t solve the problem, the culprit may be a low-quality paper. Try printing on a sheet of the manufacturer’s recommended paper, and see whether the image quality improves.

Software problems

Print dialog boxes offer a confusing array of settings, and it’s easy to overlook a check box or a drop-down menu that affects your output.

Prints have tiny puddles of ink, or the ink is runny or patchy.
Occasionally, your images may look as if they’ve been printed on very fine sandpaper. Referred to as puddling, this problem often occurs when you select the wrong paper settings in the Print dialog box or use a paper that isn’t designed for your printer. It’s particularly common with glossy paper.

To address the problem, open the Print dialog box, switch to the print settings, and verify that you’ve chosen the correct paper stock from the list. Many third-party papers include a tip sheet with recommended printer settings.

Your prints have bands of heavy ink.
Banding is often the result of printing at too high a printer resolution – especially when you’re printing on uncoated paper or art papers. This causes the printer to use too much ink. Most printers don’t let you select a specific resolution. Instead, try a lower print-quality setting.

Black-&-white images have a colour tint or appear coarse.
Although it may seem counterintuitive, colour should be turned on when you print black-&-white images. This will give you smoother gradations and richer tones than printing with only black ink.

Many printers have difficulty producing neutral greyscale images. If you notice a subtle tint when your photos come out of the printer, wait until the print has had time to dry before making any adjustments (try leaving it overnight). The colours may shift while drying and become more neutral.

If you still see a tint in your image once it’s fully dry, you may be able to adjust the colour balance from your printer’s colour-management settings (in the Print dialog box). You’ll need to experiment, so when you find settings that work for you, be sure to save them as a printer preset.

Images are darker or lighter than expected, or shadows lack details.
Your first line of defence should be to calibrate your monitor. If your images are still coming out darker or lighter than they look on screen, make sure the gamma setting (which controls the brightness of on-screen images) in your printer driver matches the one you used to calibrate your monitor. In some drivers, this setting is listed under the Color Management section in the Print dialog box. Macs traditionally use a gamma setting of 1.8, but some people prefer to use 2.2, which has become the industry standard outside the Mac world.

Because of the way papers absorb ink, dark shades of grey may appear as solid black when printed. As a result, images with heavy areas of shadows lose detail and appear too dark. For example, iPhoto books can print a bit darker than they look on screen. You can compensate for this tendency by lightening the shadows in an image editor before you print. In Adobe Photoshop, open the Levels dialog box by selecting Enhance: Adjust Lighting: Levels (or pressing Command-L). Drag the black arrow under the Output Levels scale slightly to the right to lighten the shadow areas of your image. You may need to experiment to determine the right amount of adjustment.

Understanding resolution

Improperly set resolution can lead to a host of problems, including banding, blurry or pixelated photos, or long wait times when printing. To add to the confusion, printer resolution and image resolution are two different things.

Printers measure resolution in dpi – the number of dots they lay down per square inch of paper. Depending on the printer, resolution can be as high as 4,800-x-2,400dpi. Printers reach these resolutions by layering dots on top of one another as they print. Higher dpi settings mean longer print times and more ink used, but they may not translate into a higher-quality print. Most printers don’t let you set printer resolution directly, but selecting a higher print-quality setting probably means you’re printing at a higher resolution.

By contrast, image resolution is measured in ppi, or pixels per inch. If you have too few pixels per inch, your image will appear soft or the pixels themselves will become apparent – producing jagged lines and blocky details. But there’s no benefit to having too many pixels per inch – that can choke your printer and won’t give you a better print. The ideal image resolution varies from printer to printer, but the range is between 150 and 360ppi. In Adobe Photoshop and Photoshop Elements, you adjust resolution from the Image: Image Size and Image: Resize menus, respectively.