Digital Imaging
Provides a comprehensive practical guide to the entire digital chain, from capture -- with coverage of digital cameras, to output -- with extensive information on image adjustments and colour management.
TABLE OF CONTENTS Digital Imaging
Resampling
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 'Resolution', page 9). Resampling usually takes place when the pixel dimensions of the original capture or scan don't 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 'Interpolation' (new pixel information is added based on colour values of the existing pixels).
Image scanned at correct resolution
Effects of excessive resampling
Excessive resampling up can result in poor image quality. The image will start to appear blurry and out of focus. Avoid the need for resampling up by scanning in at a high enough resolution or limiting output size. Applying the 'Unsharp Mask' filter to an image that has been resampled up can help sharpen a blurry image.
Bicubic resampling
Resampling an image so that the file size increases will lower the visual quality. If this is necessary use the 'bicubic' option in the resample preferences and limit the increase to double the original size to minimise the loss in quality. Use the unsharp mask after resampling rather than before and restrict the amount of resampling that is performed on a single image. If the software allows the user to crop, resize and rotate the image at the same time this function should...
Copyright Mark Galer and Les Horvat 2001 under license agreement with Books24x7
