Core_Computer Studies: Image Size and File Size

The size of an image and the size of a file is something that many students get confused.

This can easily happen as often when we speak of the size of an image we are actually refering to two things. Knowing the size of an image is important to understand when you either print or display an image on screen such as in a web based project.

As I have said image size takes into consideration two related things. The first is the physical size of the image the second is the digital size of the image. When we measure digital images we measure them in pixels. If on the other hand it is the physical size of an image we are interested in for instance, if you want to know it will fit on a particular page we could measure it in inches or centimeters. When we are talking about the image as part of a finished layout, however, the convention is to describe the image in millimeters.

File size on the other hand is easy to grasp as it is the number of bytes the image takes when it is stored on your hard drive or zip disk.

Here is a screen shot of image size menu box found in Photoshop. As You can see the top section of the box relates to pixel dimensions.

In other words it relates to information required for a digital life.

The bottom of the box relates to a physical size. So it relates to the size of an image printed.

These notes are written for students who undertake the Core Computer course at School of Art, Australian National University. Students of the course should feel free to contact any member of staff with comments questions and general suggestions..

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