Printer Resolution and Image Quality
Printer resolution is the number of ink dots printed on an inch of paper measured in dots per inch (dpi). Most
of today's printers have a resolution of 300 or 600 dpi. In most cases, the printer's resolution will not affect how you size and scale images. If you print your image at its actual size in inches, printer resolution will never
effect the size of your printed image.
If you want to control the quality of your printed image for a professional result such as an image destined for publication in a newspaper or magazine, you can calculate the optimal resolution for your image based on a printer's LPI (lines per inch).
For most printers there is an optimum image resolution, beyond which increasing the embedded resolution of the image (ppi) makes no discernible effect on the output quality. Each printer can only print so many lines per inch (LPI). LPI measures the number of halftone dots a printer can create in an inch of paper. Halftone dots are how a printer simulates continuous shades of colors while only using four colors: cyan, magenta, yellow, and black (some photo-quality printers also add light cyan and light magenta). Every individual pixel in your image will be represented by a random pattern of these smaller, various-sized printer dots. This process is also called screening or halftoning.
To obtain a quality print, your image resolution should be slightly higher than the printer's given LPI. To calculate this ideal resolution, multiply the LPI by about 1.5 to obtain the ideal pixel per inch (ppi) figure for your image. For example, given a 360 dpi photo-quality inkjet printer with a 150 lpi, you can get a photo-quality print if your image has 150 x 1.5 or 225 ppi. If you don't know your printer's lpi, the best way to find your optimal print resolution is to experiment. Print a test image at various resolutions to find out what your minimum ppi is for a photo-quality print. A good test image is a close up picture of a newspaper or a photo that has some angled straight edges in it.
What is Actual Pixel Size and When would I Choose It?
In the foregoing discussion, a printer's resolution (both dpi and LPI) only affected your printed image quality not size. There is one exception. In programs that can print actual size, the printer will print one dot for every pixel in your image. The size of the printed image will be determined by the printer's resolution in dpi. For example, if your printer has a 600 dpi resolution a 1200 by 1600 image will be printed to a 2" (1200/600) by 2.66" (1600/600) area.
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Selecting the Right Ink
Ink quality is an important factor in the quality of your photo print. Use the highest quality ink that you can buy, preferably from the manufacturer of your printer. Bargain inks may be older inks that have become substandard in quality. Do careful research to locate the best ink for your printer. Remove your prints promptly from the printer. Be sure to let the ink dry completely after printing, ink side up. Photo quality (nonglossy) and glossy are likely to require the longest time to dry. Once your prints are dry, insert a plain piece of paper between each print before you stack them.
You may also want to considering using the same brand of paper as your ink and printer. Printer manufacturers often go through great lengths to ensure that their inks are formulated to work with their brand of paper. This produces the best possible quality and the least fade resistance images.
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Select the Right Paper for Printing Digital Photos
There are many types of paper available for printing digital photos. Higher quality paper can result in richer colors and finer detail. Be sure to check the compatibility of the paper with your printer before using it. Paper brightness and weight are two important characteristics, with heavier, brighter stock of higher quality and price. You can choose from plain inkjet, high resolution inkjet, photo quality (usually nonglossy) and glossy. Paper cost varies widely, from a few cents per sheet to several dollars per sheet for high end specialty photo paper. You may wish to use the lower cost paper for test prints.
Glossy finish requires extra care. Handle these prints by the edges only to avoid fingerprint damage. Keep glossy paper away from water, dust and other contaminants. Be sure to print on the correct side of the page, which is generally shiny.
Take good care of your printer paper stock. Store it in the original packaging, away from hot or humid conditions. Make sure the package lays flat.
Is mention in the article about selecting the right ink, you may want to consider using the same brand of paper as your printer manufacturer. This ensures the best possible prints.
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Common Mistakes in Printing Digital Photos
Incorrect Printer Settings
Printer settings should be optimized to use the specific printer on which you are printing. Check the printer output resolution (dots-per-inch or DPI) recommended by the manufacturer of your printer, and specify this setting in your printing software. Select the paper option (photo paper, etc.) that matches the paper loaded in your printer.
Scale Factor
Scaling up the size of the photo decreases the print quality. Your photo is made up of tiny points of picture information, called pixels (short for “picture elements”). The resolution of your image is measured in pixels-per-inch (PPI). The higher the PPI, the greater the detail of the photo. When you enlarge your picture with your editing software, the original pixels are spread out and the software fills the space between each pixel with new pixels. These new pixels are generated by the computer by estimating which color would be best for each new pixel. The resulting pixels are spread out over an even greater space, and the image becomes less clear because of this estimation by the software. This process results in lower quality in your printed photo.
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Grayscale / Black and White Printing
If your printer isn't designed to specifically to print in grayscale, you may want to considering having your images printed at a photo lab.
Inkjet printers that are designed to print in greyscale use black ink along with light-black or gray ink to produce the tones.
Inkjet printers that aren't designed to print in greyscape use only black or black ink along with additional colors to produce the various tones. This ultimately leads to a slight color cast in your images.
When buying a printer for your images, you may want to check to ensure the printer has grayscale printing capabilities otherwise it is best to send your images to your local photo lab.
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