How to resize images in Photoshop and Elements

You need to open up the "resize image" box. In Photoshop it's under Image > Image Size. In Elements go to Image > Resize > Image Size.

This box caters for two entirely different types of resizing. In both of them you should have "Scale Styles" and "Constrain Proportions" ticked.

Firstly, it lets you to define the size of a print of the image. To do this, make sure the "Resample Image" box is unticked, then key in the dimensions of the print in the Document Size box. If you'd prefer a different unit of measure (eg inches instead of cm) just click the little arrow and pick your favourite.

Keep an eye on the resolution box. If your resolution drops below about 200 dpi the print will look grainy, and below 100 dpi it'll look more like a pebbledash wall than a photo.

It's not normally necessary to save the image file after changing the print size. It doesn't change the information in the file, just the print size, and you can change it as often as often as you like without degrading the image.

Secondly it allows you to change the number of pixels in the photo. Usually this is done to get a smaller version of the file, for instance to send to someone on email and allow them to view it easily, or to prepare the image for projection on the club's digital projector.

It's a more radical procedure because you're altering the image itself. If you reduce the number of pixels and then save the file under its original name, you can't go back again. The information just isn't there. So when you've reduced the number of pixels make sure you use "Save As" and give the file a new name.

The main difference is that now you need the "Resample Image" box ticked and you specify the size in the "Pixel Dimension" fields.

PS: Ignore the reference in the screen shot to "Chroma", which was an exhibition we ran in 2008. Any photo which'll be viewed through a browser or email should have a long edge of about 600-700 pixels or it'll be too big to fit on the screen.

-- RodBird - 17 Sep 2007

How to do it with ImageMagick

ImageMagick is a command-line tool so it is much easier:

    mogrify -geometry 600x600 something.jpg

Resizing with The Gimp

This is very similar to the Photoshop process described above. For details, see Resizing Images with The Gimp

-- AndrewFindlay