When you change the size of a digital file your software either adds pixels when increasing the size or removes them when making the image smaller. This scaling process is known as Interpolation and relies on Photoshop (Photoshop Elements) knowing which pixels to add or dump. There are now five methods of interpolation in Photoshop/Photoshop Elements u2013 Nearest Neighbor, Bilinear and Bicubic, with Bicubic Smoother and Bicubic Sharper which were first added in Photoshop CS and Photoshop Elements 4.0. Photoshop users can alter the default method used when changing image sizes by going to Edit > Preferences > General. Photoshop Elements users can only alter this option when scaling using the options in the Image > Size dialogue
01 The default setting used for up- or down scaling images can be altered in the Edit > Preferences > General dialogue of Photoshop. Photoshop Elements users aren’t able to alter the default but can change the specific setting used in the Image Size dialogue at time of scaling. The options are:
offers the fastest method by copying the adjacent pixels, but results are often poor. Good for upscaling screen shots but not much else.
looks at pixels above and below plus left and right and averages out the result to give an intermediate pixel and a smooth blend.
looks at all the pixels surrounding each pixel and averages them all out to create the new ones. It then boosts contrast between each pixel to reduce softness.
is variation of Bicubic and is designed to be used when you enlarge the image.
is yet another variation of the Bicubic setting this time customised for reducing the size of photos.
Edit > Preferences > General
In Photoshop Elements:
In the latest version of the software it is not possible to change the default scale settings.