Understanding Photoshop Images

Any image found on a computer is called a DIGITAL image. For example, an image that ends in the extension “.jpg”, “.tif”, “.psd”, “.bmp”, and “.ai” are all digital images.

Raster images
However, different programs create different types of digital images. Photoshop creates RASTER images. Raster images are created using a grid which is called a BITMAP. This bitmap is made up of many squares which are called PIXELS.

Pixels
Each pixel is only one color and has a certain number of bits (which is how the image is measured in bytes).

Image size
Information about the image can be found under Image > Image size. You can find out the file size, the resolution, the width and height, and the number of pixels in the image. You can also make changes to any of these dimensions.

Resolution
It is the sharpness and clarity of an image. It is measured based on the number of pixels per inch. Standard print resolution is 300 dpi, whereas, the web uses a lower dpi of 72. The pro of low resolution is smaller the size and the con is lower quality. The pro of higher resolution is the good quality of the image, but the con is the larger the size.

Resolution is determined by the number of pixels in an inch. And as you can see in this image below, there are much
smaller and more pixels in the higher res image. Whereas, in the lower res image, there are fewer and bigger pixels. This makes the image look bad (pixelated).

FInding images on the Internet
When searching for images on the Web, make sure to look for medium/large images and then get the full size, not just the thumbnail.