Resolution & Print Size Primer
Image resolution is represented in dpi. This is the number of dots of information - in this case, pixels - that are stored in a given unit of space. A pixel is a dot on the screen that displays a single color. An image is made up of many pixels. For example, a 6" x 4" image at 100dpi is made up of 600 x 400 (240,000) pixels. A computer screen does not represent images in inches or other units; it instead displays in pixels. For example, most moderns are able to display 1024x768 pixels simultaneously. This means it displays 1024 pixels horizontally and 768 pixels vertically, independent of the actual size of my monitor itself or the picture that is being displayed.
Print Size is the size of of an image in print form. The pixel count of an image displayed on a screen is found by multiplying the print size of the image by its resolution (size x dpi = pixel count). An image containing 600x400 pixels at 100dpi would print at 6" x 4".
Compare the following three images. These three images share the same print size (6" x 4"), but each has a different resolution. The file at 100dpi is larger than the 72dpi file, even though the print size is the same.
-
A 6" x 4" image at 100dpi
-
A 6" x 4" image at 96dpi
-
A 6" x 4" image at 72dpi
Compare the following three images. All the images have the same resolution, but because of the decreasing print sizes, the first is larger than the last.
-
A 6" x 4" image at 100dpi
-
A 3" x 2" image at 100dpi
-
A 1.5" x 1" image at 100dpi
The following sets of three images each all have the same print size, but their resolutions are different. The dpi is directly proportional to the size of the image as shown on your screen.
|
|
Different images can have different print sizes and dpi while still maintaining the same images size onscreen. All of these images occupy 300x200 pixels, yet they have different print sizes and resolutions.
-
A 3" x 2" image at 100dpi
-
A 3.125" x 2.083" image at 96dpi
-
A 4.167" x 2.778" image at 72dpi
