Digital Movies across the Curriculum

In the early days of computing, a file format for displaying picture known as bitmap was developed. Bitmap files are made up from tiny dots called pixels effectively mapping the colour and position of every pixel in a picture using grip references similar to that used in mapping. Obviously the greater the detail desired, the greater the amount of information stored and the larger the file would be.

However, because bitmaps files store information about EVERY pixel, they can be very large and this makes them unsuitable for use on the internet where bandwidth is at a premium. A professional body called the Joint Picture Expert Group developed the JPEG format which addresses the problem of large file sizes by extrapolating areas of the same colour and mapping the whole area as one rather than mapping each individual pixel. Use ‘Save As’ in your picture editing software to convert bitmap (.bmp) files to JPEG (.jpg) whenever possible as this will save space in your computer or network area without necessarily sacrificing picture quality.

The more dots used in digital pictures, such as JPEG’s or bitmaps, the clearer the image will be. Pictures may be rendered in, say, 600x800 or 1200x1600 pixels. This is known as the resolution of the picture. Typically a digital camera takes pictures with between one and five million pixels.

The main limiting factor on picture resolution (apart from the device creating the picture in the first place) is that the sharper the resolution (the more pixels) the bigger the image file will be. Storing sharp pictures takes up more computer storage space than less sharp pictures. Most picture editing software will easily let you reduce the resolution (it is more difficult to put detail in that isn’t there already) and this might be wise when storing pictures on a school network for students to use. You must decide on a compromise between picture quality required and size of files used.

It is desirable to limit the size of files used by students. Don't just copy files off their digital cameras without looking at the file sizes first. There are three main issues:

Some of the pictures may benefit from cropping (or indeed rotating) to just show the key subject before they are included in a video presentation
If your students make files that are too big they may crash the computer that they are working on and loose their work. This can be demoralising and time wasting. All video software crashes easily in my experience regardless of the power of the computer.
There may well be a storage implication with available storage on your server and suddenly flooding your network with large sources files and finished movie projects might upset your network manager