Wombat Outdoor Adventures

Quick Guide to

Screen Colour Problems

Okay, so either you are seeing funny colours on the pictures on these pages, or you are wondering what the numbers mean, or you just like following links to see what is there (Hello explorer {:-).

If you see funny colours, or pixelisation (chunky colour blobs), this means that the amount of video memory in your computer is insufficent for the colour depth of the pictures. If you are still puzzled, read on.

Your monitor will most probably display what is stored in ram chips on a separate card in your computer. This is your video memory. Sometimes, what can be displayed is limited by the amount of ram on the video card. Other times, it might be limited by the settings you have chosen, or has been chosen for you. These are not something you can change immediately, but you may be able to view a lesser quality version of the picture by choosing the 256 colour version, rather than the full colour version.

If this does not fix the problem, sadly you will not be able to view the images provided until your video memory is upgraded. If you want to understand the problem more fully, please continue reading.

Firstly, we are going to have to talk about Image Sizes. The numbers floating around actually give you the approximate size of the images in pixels. Pixels are how the resolution setting of your screen is described. If you have a VGA screen, then what you are seeing is made up from 640 columns of pixels across the screen and 480 rows of pixels down the screen. This gives 256,000 pixels that are fired up to display information on your screen.

Similarly, SVGA is 800 columns across and 600 rows down, or 480,000 pixels. Now, we normally just measure the resolution in pixels, so the next standard screen setting is XGA, which is 1024 x 768 pixels, or 786,432 pixels all together. Now you have a background on the first part of image sizes, which is resolution.

Colour Depth is simply the amount of information that the computer has to transfer to display each pixel. Have you ever used an older mono (one colour) screen? These might have been green, orange or white. In all cases, the background (pixel off) was black. To display a mono colour screen, the computer only has to turn each pixel on or off. Turning a pixel on or off only requires one (1) BIT in computer jargon.

To get colour, a computer screen uses mixtures of three colours; red, blue and green. In a good modern screen, each of these colours can be fired at 256 different levels to help make up over 16,777,216 colurs. This is know as Full Colour.

To display Full Colour, a computer has to pass three BYTES (1 byte = 8 bits, 8**2=256) for each pixel it wants to display. Head spinning? Don't worry about.

In short, to display 800x600 pixel resolution images, you will need a 2 Mb (megabyte) or higher video card and software set to use it. To display a 1024x768 image, you will need a 4MB or higher video card.

Not every computer needs these, so we've created a version of most images in 256 colour. For this, the computer only passes one byte for each pixel. So provided you have at least a 1Mb (one megabyte) video card, you should be able to view the 256 colour version of whatever resolution your screen is set to. The different versions are for people who may like to keep a copy of the image as a background screen or as a screen saver picture.

We would appreciate feedback on this explanation, but can not offer to help people with particular problems.

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