Bitmap Images - JPGs

A bitmap image is an image made up of hundreds of dots, the most common type is JPG, and now the industry standard image format. JPGs are the only format supported.

There are three main things that define the quality and size of a JPG:

• The size of image: How big is the actual image, just like a photo, it might be 6x4 or it might the size of poster.
• The DPI: or dots per inch. This effects the number of actual dots that make up the picture.
• The compression: JPGs are great because they are compressed the images, but compress them too much and you lose quality and can cause issues with the software.

You can imagine a JPG image like a balloon with print on it. If you blow the balloon up, the print gets stretched, it might distort and the colour becomes lighter. Let the air out of the balloon and the effects are reversed. Your JPG is the same, if you increase its size, it may distort and the colour might alter. This is particularly obvious on straight lines and text.

An image may also look pretty good on a screen, but, look poor when printed. This is because most screen resolution images are only 72 dpi, where as print is usually 300 dpi.

The problem can be as bad the other way though, you might take a digital image at 600 dpi, then shrink it by just dragging its corners. The image, though it looks smaller, still has the same number of dots, so you may now actually have a 1200 dpi document. Simply put, this means you are uploading larger images than you need, so uploads take longer, previews take longer.

The general guide lines for images are:

• Most JPGs need be no more than 250 Kb in size (exceptionally you might want them bigger if you are using them are very large print i.e. posters).
• The size of the JPG should be roughly the size that it will be used in the final artwork, for most of our work that 150mm wide by 100mm tall.
• The DPI needs only to be 250.

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