# Section 107. Change Image Size or Resolution

107. Change Image Size or Resolution

BEFORE YOU BEGIN

75 Scan In Photos

108 Change the Working Area Without Affecting Image Size

As you learned in 106 About Size and Resolution , an image's size is tied directly to the number of pixels in the image as well as the relative size of the pixels. When you create images with a digital camera or scan printed images with a scanner, you choose the resolution you want to usefor instance, 300ppi. The resolution you choose also determines the resulting print size. For example, an image that's 2048 pixels wide by 1536 pixels tall (the typical dimensions of an image taken with a 3 megapixel camera), whose resolution is 300ppi, will print at 6.827" by 5.120".

NOTE

To calculate the print dimensions of an image yourself, take the image size in pixels and divide it by the number of pixels per inch. To display an image in its print size, click the Zoom tool on the Toolbox and then click the Print Size button on the Options bar. To view an image's size in pixels, resolution, and print size, display the Image Size dialog box by choosing Edit, Resize, Image Size .

So what do you do if you want to print your image at a different sizelarger or smallerwhile maintaining or even increasing its resolution to, say, 300dpi? Answer: You use resampling. When you use resampling to increase an image's print size and/or its resolution, new pixels are inserted between existing ones. The Editor determines the colors for these new pixels by sampling the color value of each surrounding pixel, calculating a value within the sample range, and assigning that value to that new pixel. Conversely, when you reduce an image's print size, resampling removes pixels from the image and then adjusts the colors of the pixels remaining in the image by approximating the blended color values of the pixels that were removed.

KEY TERM

Resampling The mathematical process applied during image resizing that evaluates the content of the pixels in the image in order to calculate the value of new pixels (when enlarging) or neighboring pixels (when reducing), and which reinterprets the result to minimize loss of detail.

107. Change Image Size or Resolution

Because resampling is based on best-guess estimation, using it to change an image's size or resolution by more than 20% often produces poor results. You can resize or change an image's resolution without resampling by telling the Editor that you want to turn resampling off, and therefore maintain the relationship between the size and the resolution. In this manner, you can double an image's print resolution by cutting its print size in half (the image will contain as many pixels as it did before, but the pixels will be smaller, and there will be more of them per inch). Onscreen, you won't see any apparent change at all.

TIP

One fast way to remove moir ƒ patterns , fuzziness , and spots created when you scan an image is to scan at 600dpi and then reduce its resolution to 300dpi while maintaining its print size .

TIP

If you want to print an image in some size other than its normal print size, you can "rescale" the image on the fly when you print it. If you print an image in a larger size than normal, however, the resolution is decreased proportionately to compensate (pixels are not added). If the resulting resolution falls below acceptable levels of quality, you'll see a warning, so that you can choose a different print size. Regardless, with this method, the original resolution and print size of the image are left unchanged. If you get the warning, it's best to abandon printing and then resize and resample the image to the print size you want, by following the steps in this task.