Resampling Upward - is it possib

Resampling Upward - is it advisable?

Photoshop's Image>Image size dialog box lets you change the number of pixels when Resample Image is checked. You can decrease the number of pixels when you want a smaller picture (i.e. a thumbnail for a web page). You can also increase the number of pixels in a picture too, but is this wise?

Here is a small picture - perhaps something found on a web site. It is only 200 pixels wide. (Remember that web browsers care only about how many pixels are in the picture. A 200 pixel wide picture will generally occupy 200 pixels onscreen in the majority of web browsers. Apple Retina devices and other unusual portable devices sometimes resample images on the fly.)

Now let's open the Image>Image Size dialog box in Photoshop, and click Resample Image. We intend to upsize the picture to make it bigger.

Units were changed to Pixels in the Image Size dialog. The desired 800 pixels has been typed directly into the Width field, and Height changes proportionally to keep the picture from stretching. Note that the file size shown at the top indicates that the picture has grown from 83.2K to 1.30 MB.

Now let's see how it looks after resizing...

Ewww! That's an ugly, fuzzy result.

Upsizing pictures doesn't work well. You may be able to get away with ~20% upsizing without anyone noticing a drastic change, but it's best to start from larger originals if you can.

Of course downsizing (Resampling downwards) works fine. The first picture (the small one) shown in this example was downsized from a much larger camera picture. If I really wanted an 800 pixel wide picture, I should have started with the camera original and downsampled to meet my needs.

Avoid upsizing!