Photoshop CS3

essential skills: photoshop CS3 9LZHTWSPUN

An image is ‘resampled’ when its pixel dimensions (and resulting file size) are changed. It is possible to change the output size or resolution without affecting the pixel dimensions (see ‘Understanding resolution’). Resampling usually takes place when the pixel dimensions of the original capture or scan do not precisely match the requirements for output (size and resolution). Downsampling decreases the number of pixels and information is deleted from the image. Increasing the total number of pixels or resampling up requires new pixels to be added to the file. The new pixels use information based on color values of the existing pixels in the image file.

Image scanned at correct resolution

Effects of excessive resampling up

Excessive resampling up can result in poor image quality (the image will start to appear blurry). Avoid the need for resampling to enlarge the file size, if at all possible, by capturing at a high enough resolution or by limiting the output size. If you have to resample due to the limitations of your capture device (not enough megapixels) then files that resample best are those that have been captured from a digital camera using a low ISO setting and have not previously been sharpened.

When resampling up an image to create a larger file, choose the ‘Bicubic Smoother’ from the Interpolation options in the Image Size dialog box. Use ‘Bicubic Sharper’ when decreasing the size of the file. Bilinear and Nearest Neighbor are used for hard-edged graphics and are rarely used for the interpolation of photographs. If you have already sharpened your image prior to resampling (best avoided) you will need to reapply the Unsharp Mask or Smart Sharpen to regain the sharp quality of the image.

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