What is a raster image?
Sit back and enjoy the video as we answer the simple, yet important question, “What is a raster image?”
Almost any photo you see on the internet is a raster image, and common file formats are .jpg, .gif, .png and .tiff.
A raster image is composed of millions of tiny squares called pixels.
Each pixel represents a single color, and together, they create an image.
Another term you’ll hear when working with raster images is bit-depth, which refers to the amount of color information available.
The higher the bit-depth, the more colors the file can store.
You’ll notice in Photoshop you have the option to set bit-depth when creating a new document.
An 8-bit document is able to display 16.8 million different colors and 16-bit image is able to display trillions.
For most images 8-bit is all you need, so why would you ever use 16-bit?
Flexibility when editing.
If you’re making a lot of edits to an 8-bit image you’ll eventually run into a problem called posterization.
Posterization is when an image’s apparent bit-depth decreases and results in poor color transitions.
You can see here that after a few adjustment layers that the image begins to lose color information in the sky.
One way to avoid this is to edit RAW files in a higher bit mode like a 16-bit mode.
Keep in mind, JPG images are already 8-bit, so converting it to 16-bit has no benefit because that color information is already lost when it was saved as a JPG. Therefore, be sure to edit RAW files if you want the maximum color flexibility when editing.
So should you always edit in higher bit modes? Well, it depends.
Use 8-bit if you’re doing minimal adjustments to an image and if computer performance is a concern.
And use 16-bit when you’re doing heavy editing and computer performance is not a concern.
If you liked this quick-tip you should check out the one below. It explores the best way to make images more vivid without overdoing it with saturation:
