GIMP Bit Depth: 8, 16 or 32 Bit? {Complete Guide}

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There seems to be mass confusion about Bit Depth and which settings to use; 8 bit, 16 bit, or 32 bit. I’m about to take the mystery out of bit depths! You’ll discover which one you should use (and why) once and for all!

Which one should you use? There are pros and cons for each!

Once you’re done reading this article about bit depths in GIMP, you’ll know exactly which one to use and why! If you’re ready… let’s do it!

Table of Contents

What Is a Bit Depth?

Before we can delve into which one to use, we first need to establish a foundation from which to build. This will give you the knowledge to make the right choice.

A bit depth is not a feature limited to GIMP. It’s more of a universal truth regarding digital photos and your software of choice for editing.

Bit Depth

Click the image to enlarge. Notice how the larger bit depths have a smoother transition from black to gray to white.  Higher bit depths utilize more colors and reduces banding (more on that coming up).

In essence, a “bit” represents how much color information is available for each pixel in a photo.

The higher the number of bits per pixel results in more available colors from which to edit with. A higher number of bits also results in a more accurate color rendition from one shade to another.

The downfall to higher bits is the resulting image file size. This is due to more information per pixel as the number of bites increases.

Ones & Zeros

code

On a basic level, your computer’s brain functions with the help of binary code… ones and zeros. These numbers are how your computer communicates and displays data on your monitor.

In our digital photography world, your photos are also made up of ones and zeros. The arrangement of these numbers displays the colors and brightness of your photos.

It takes a combination of three primary values (RGB) to create the colors in your images. The greater the number of ones and zeros in each of these primary values will result in more colors!

RGB

The three primary color values are Red, Green, and Blue (RGB). Each is recorded separately (or in its own channel) and mixing them results in a new color.

Bit Depth Deep Dive

In GIMP, we have three central bit depths to work with; 8, 16, and 32. Each level will increase the number of colors.

You also have to consider that each RGB channel consists of 256 shades of color. When you multiple each channel amongst each other… 256 x 256 x 256, the result is 16.7 million possible color values!

A 16-bit image has 65,536 possible values per channel. Multiplying each channel together provides 2.8 trillion colors!

32 bits is insane at 4.29 billion colors per channel that spit out, well, more numbers than my calculator could provide.

Your Eyes Can't See That Many Colors!?!?

We’ve established that more colors are better. The only problem is, your mortal human eyes are only capable of seeing 10 million colors!! So, even an 8-bit file produces more colors than humanly possible to decipher.

Oh, and that 4K or 5K monitor you’ve been eyeing (or using) also displays more colors than you can see!

eye color change

What's the Point of All Those Colors?

Now the real question is, why do you need all those colors in the first place? The answer lies in how your mind sees the transition of colors vs. how a computer (or camera) sees them.

Remember, a computer monitor is displaying what you see in ones and zeros. The more data it has to output for you to see, the smoother the values will be. A less smooth transition results in banding…

Banding

Banding

Notice how the color transition, in the sky, from light blue to dark blue is jagged… this is banding.  This occurs when you over edit an image or if there isn’t enough colors for a smooth transition.

Banding occurs when the transition from one color to the next is noticeable. It will look rough or jagged… this is due to not having enough colors to fill in the gaps!

The solution is editing with more colors. When you do, your computer can fill the gaps for a smooth color transition (that you can see).

Which Bit Depth Should You Use?

More is better. Or is it?

In 30 years of digital editing, I’ve used 16 bit less than a dozen times and 32 bits… never! And no, I’m not spewing out crap. The difference is knowing when to use 8 bit vs. 16 bit vs. 32 bit.

Edit In...

Often, you’ll find banding occurring when there’s a solid color of one shade. Like skies, a solid wall, or other surfaces with one prominent color.

If you plan to do a lot of editing with these types of images, I’d suggest converting your file to 16 bit.

Pro Tip:

Banding is also more likely to occur the more you edit the same image. This occurs due to stretching the tonal range of an image beyond the colors available. Which creates gaps or the banding.

For example, if your image is extremely over or underexposed, you’ll need to fix it beyond its existing colors. Switching to 16 bit will introduce more colors to close the gaps.

You're Editing In 8 Bit & Notice Banding

If you start editing in 8 bit and begin noticing banding, it’s too late. There are two solutions to overcome this (in the future).

  1. Always use pro editing techniques by working non-destructively. This means, don’t edit on the original image layer.

    Instead, duplicate the layer for every type of edit you plan to do. This way, you can repeat the editing steps with a duplicate file at 16 bits.

  2. If you find most of your images result in banding, you may want to always convert to 16 bit from the start. Make sure to add this step to your workflow, so you don’t forget.

Pro Tip: RAW vs. JPG

When converting a RAW file to JPG, it automatically becomes an 8-bit image. This is due to JPGs being compressed when saved. However, you can still convert the 8 bit to 16 bit. When you do, the image will look exactly the same.

It’s not until you begin editing that GIMP will start using the additional color values. You won’t see the benefit of editing in 16 bit since banding will be virtually impossible to see. It’s not until you edit the same image in 8 and 16 bits, side-by-side when you’ll notice the effects.

The Ugly Side to Higher Bit Depths

We’ve already established one reason not to use higher bit depths… increased file size. It’s not so much the size itself since hard drives are getting less expensive every year.

The unforeseen dilemma with larger files is the performance issues you’ll encounter with GIMP. The bigger the file, the slower GIMP becomes. It will be more evident if your computer resources are limited: a small amount of RAM, hard drive space, SSD vs. external, and more.

Now What?

Now that you know which bit depth is best for you, there’s another aspect of editing you should know about… color space. At this time, GIMP 2.10 doesn’t have much in the way of managing color spaces. This is going to change with GIMP 3, and I’ll have an article about that here.

Like this article? If so, please share!

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Hello! My name is Chris Parker and I run this place. But, more importantly, what’s in it for you? Well, my passion is to help you achieve your creative vision.

With 30 years experience I believe I can help you do just that. So, if you’re ready… let’s do it!

 

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One Response

  1. I was worried that I should be using a higher bit number. This helped me realized that I should be just fine most of the time with 8 bit. Though I am wondering if 16 bit would be better when using the smudge tool for digital art. I just started using GIMP 2.10.22 after years of sticking with 2.6 for digital art for surface design.

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