Aspect ratios

Here’s a quick note on what aspect ratios are and how they apply to planning a screen-based slideshow or presentation. It follows up on my previous post on ProShow Gold 4.1 and explains what I meant when I said that the first step in planning a slideshow is to consider the aspect ratio (or shape) of the screen you are going to show it on.

The aspect ratio describes the shape of a screen (or print for that matter) by stating how many units wide and high it is. A widescreen display is 16 units wide by 9 of the same units high (16:9) or, to put it another way, they are very nearly twice as wide as they are high. You can get big ones and small ones, but they will all have the same basic shape. By contrast, conventionally-shaped computer and television have screens which are 4 units by 3 units high (4:3).

The snag is that the pictures produced by most digital cameras are a different shape again, being 3 units wide by 2 units high (3:2). Screen and pictures different shapes; a big problem!

The diagram below shows what happens when you try to fit a 3:2-shaped picture onto a 16:9 screen:

You either have to leave some screen space unused or lose some of your picture. The same applies if you try to fit the same-shaped picture into a 4:3-shaped screen:

The solution is either to use layouts which have more than one picture in them, or to explore different cropping options for your images, such as in the picture below:

Slideshow software will often crop images arbitrarily but some, such as ProShow Gold, allows you considerable freedom in deciding how your pictures will be zoomed and/or cropped. It will also allow you to create layouts with more than one than one picture in them (using styles).

Failing that, you always have the option to create layouts with the desired aspect ratio and number of images in software such as Photoshop or The Gimp, and importing these into your slideshow software.

NOTE: All the above applies to prints as well. A 3:2 picture will not fit accurately on an 25x20cm (5:4 ratio) print, for example.

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