THIS IS WAR. Wyatt Miranda gets a piggyback ride from fellow senior Cole Clinton during the homecoming pep rally. The seniors’ cheers won them the spirit stick. Photo by Dong Whee Won, Arrowhead Christian Academy (Redlands, Calif.).
Images improperly sized look blurry, fuzzy — just bad BY BRADLEY WILSON, MJE
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eith Carlson, CJE, asked a question on JEAHELP that media advisers have asked many times over the years. “I just received my September print issues for next week and discovered that most of the images look really blurry. The students were having a hard time getting photos and art to show up in high quality. “While in InDesign, they would save things in high quality and pages would look great. But then, when they would PDF the files/export them to be sent to the printer, everything that had been saved as a high-quality image looks blurry.” Understanding the fundamentals of digital resolution is critical to understanding the best resolution for saving images to maximize quality output. At the time a photographer clicks the shutter on a digital camera, the amount of digital information in that
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image is fixed. It will never contain any more information than at that time. Still, time after time, page designers try to enlarge photos beyond the original size resulting in a loss of quality. When a photo is enlarged in a page-layout program, the pixelation (“jaggies”) becomes evident. Fortunately, today’s page-layout and digital-photography software packages make it easier to determine whether the image has enough resolution. For example, if you know a photograph is going to be printed in a newspaper that uses a line screen of 85 lines per inch (information obtainable from the printer) and you know it’s going to be about 4 inches by 6 inches in size, you can size it with that information in mind. Except for the largest images in high-quality magazines (or yearbooks) most digital SLR cameras, when set to capture images at the highest resolution, contain more
information than all websites and most newspapers could possibly use. Some people are taught to sample everything at 300 PPI regardless of the output resolution or file size. This uniform approach presents its own set of problems, not the least of which are slower operating speeds and an increased chance for disk errors because the file size will be much larger than necessary. Larger files are slower and prone to error. For example, a 3-by-5 inch photograph at 300 PPI will occupy 1.29 MB but only 424 KB at 170 PPI (about one-third of the disk space). The smaller file size results in faster operations and less chance for disk errors. Further, it does not give designers an actual representation of the largest size at which they can actually use the file. In short, they learn bad habits about enlarging and reducing photos on the page. To be most efficient, media producers need to develop a workflow continued on page 34
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Definitions
NOTE THE EFFECTIVE RESOLUTION IN PPI
PIXEL
A combination of two words: picture and element; the smallest component of a digital image; defined in three dimensions: hue, lightness and saturation
LPI
Lines per inch; reserved for the number of lines in a screen of a printed image; determined by the maximum resolution of the press on which the page is being printed photocopy........................... 65 LPI newspaper........................... 85 LPI yearbook.............................150 LPI
DPI
Dots per inch; reserved for the number of dots available in output of a laser printer or other output device laser printer..................... 600 DPI imagesetter................... 2400 DPI
PPI
Pixels per inch; the number of “picture elements” in an image as it appears on the screen Web image.......................... 72 PPI photocopy......................... 130 PPI newspaper......................... 170 PPI yearbook...........................300 PPI
When an image is enlarged and not resampled, the pixels that make up the image become evident. In the example on the left, Photoshop extrapolated from a smaller image a full-size image, making up the missing date. In the example on the right, the image was enlarged on the page (340 percent). continued from page 33
that achieves two goals: (a) retain the original image that is properly named and captioned for historical purposes; and (b) save a copy of the image in the appropriate resolution and color mode for each media. For example, if a photo is used in the yearbook and on the yearbook’s website, the staff will need three copies of the image: the original saved on an archived hard drive, one sampled at 300 PPI saved in the appropriate folder for that spread and one sampled and downsized at 72 PPI
saved in an online media folder. Of course it is also possible that the problem with pixelated images lies not on the input side but on the output side. InDesign requires access to the high-resolution data at the time of printing (or when making a PDF). Missing files will result in error messages. Finally, the resolution of the PDF file can be changed in the Compression portion of the Print dialog bix, where setting the PPI for output should correspond to the desired LPI. n
Formulas The MAXIMUM RESOLUTION of a printer 10 percent x DPI = LPI Example: A 600 DPI printer can output a maximum of 60 LPI (10 percent x 600 DPI) and still retain all 256 levels of gray.
Number of PIXELS NEEDED in an image at actual size LPI x 2 = PPI ENLARGEMENT/REDUCTION LPI x percentage of enlargement/reduction x 2 = PPI
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