The difference between the 8 bit and 16bit images

Digital cameras, or at least professional digital cameras, have the ability to shoot in RAW format for several years now, allowing you to open images in Photoshop and edit them in 16 bit mode, rather than 8 bit mode, as you usually do with standard jpeg images.

Despite this, many photographers, even professional ones, still make their JPEG images, even if their camera supports RAW format. And although there are quite a few weighty arguments when choosing JPEG versus RAW — a high shooting speed and a much smaller file size — the first thing that comes to mind is that many people still shoot JPEG just because they don’t understand the difference between image editing in 16 bit mode. In this lesson, we just sort out the difference.

What does the term “8 bit” mean?
You may have previously heard the terms 8 bits and 16 bits, but what do they mean? When you take a picture on a digital camera and save it in JPEG format, you create a standard 8 bit image. The JPEG format has been around us for a long time with the advent of digital photography and even during the improvement of Photoshop, but recently its flaws have become more and more noticeable. One of them is the inability to save a JPEG file in 16 bit format, since it simply does not support it. If this is a JPEG image (with the extension “.jpeg”), this is an 8 bit image. But what does “8 bit” mean?
If you read our lesson “RGB and Color Channels,” you know that each color in a digital image is created from a combination of three basic bright colors – red (red) green (green) and blue (blue):

It doesn’t matter what color you see on the screen. It was still made from some combination of these three colors. You might think, “This is impossible! My image has millions of colors. How can you create a million flowers just from red (red) green (green) and blue (blue)? “

Good question. The answer is to mix shades of red, green and blue! There are many shades of each color with which you can work and mix with each other, even more than you can imagine. If you had pure red, pure green and pure blue, all you can create is seven different colors, including white, if you mix all these three colors together.

You can also include the eighth color, black, which you could get if you completely remove red, green, and blue.
But what if you have, say, 256 shades of red, 256 shades of green and 256 shades of blue? If you make mathematical calculations, 256x256x256 = 16.8 million. Now you can create 16.8 million colors! And this, of course, is what you can get from an 8-bit image – 256 shades of red, 256 shades of green and 256 shades of blue give you the millions of possible colors that you usually see in the photo:

Where does the number 256 come from? So, 1-bit is set to 2. When you move from 1 bit, you find the value using the expression “2 to the power (number of subsequent bits).” For example, to find the value of 2 bits, you need to count “2 to the power of 2” or “2×2”, which equals 4. Thus, 2 bits equals 4.
The 4-bit image will be “2 to the power of 4”, or “2x2x2x2”, which gives us 16. Therefore, 4 bits equals 16.

We do the same for an 8-bit image, it will be “2 to the power of 8”, or “2x2x2x2x2x2x2x2”, which gives us 256. That’s where the number 256 comes from.
Do not worry if it seemed confusing, incomprehensible and boring. This is just an explanation of how the computer works. Just remember that if you save a JPEG image, you save it in 8bit mode, which gives you 256 shades of red, green and blue, 16.8 million possible colors.

So, it may seem that 16, 8 million colors are a lot. But they say, everything is known in comparison, and if you have not compared it with the number of possible colors of a 16-bit image, then you can say you have not seen anything yet.

As we just realized, saving the photo in JPEG format, we get an 8 bit image, which gives us 16.8 million possible colors.
It seems that it is a lot, and it is so, if you think that the human eye cannot even see so many colors. We can distinguish only a few million colors, at best, with certain skills, a little more than 10 million, but not 16, 8 million.

Therefore, even an 8 bit image contains much more colors than we can see. Why then do we need more flowers? Why is not enough 8 bits? So, back to this a little later, but first, let’s look at the difference between 8 bit and 16 bit images.

Earlier, we found out that an 8 bit image gives us 256 shades of red, green and blue, and we got this number using the expression “2 to the power of 8” or “2x2x2x2x2x2x2x2”, which equals 256. We will make the same calculations in order to find out how many colors we can get in a 16 bit image. All we need is to find the meaning of the expression “2 to the power of 16” or “2x2x2x2x2x2x2x2x2x2x2x2x2x2x2x2”, which, if you count on the calculator, is equal to 65,536. This means that when we work with a 16-bit image, we have 65,536 shades of red , 65,536 shades of green and 65,536 shades of blue. Forget about 16.8 million! 65,536 x 65,536 x 65,536 gives us 281 trillion possible colors!

Now you might think: “Wow, this is certainly great, but you just said that we can’t even see the 16.8 million colors that an 8-bit image gives us, are these 16-bit images really important, giving us trillions of colors that we can’t see? ”
When it’s time to edit our images in Photoshop, this is really very important. Let’s see why.

Editing mode (mode) 16 bits.
If you have two identical photos, open them in Photoshop, the difference should be that one image should be in 16 bit mode with its trillion possible colors, and the other in 8 bit mode with its 16, 8 possible colors. You must have thought that the 16-bit version should look better than 8-bit, because it has more colors. But the fact is obvious that many photographs simply do not contain 16.8 million colors, not to mention trillions of colors for accurate reproduction of image content.

Usually they contain several hundred thousand colors, at best, although some may reach several million depending on their content (and also depending on the size of the photo, since you need millions of pixels to view a million colors). Plus, as you already know, the human eye cannot see, at least 16.8 million colors. This means that if you put two 8-bit and 16-bit images side by side, they will look the same to us.

So why is it better to work with 16 bit images? One word is flexibility. When you edit an image in Photoshop, sooner or later, if you continue editing it, you will encounter problems. The most common problem is known as “grading”, when you lose a lot of detail in the image, after which Photoshop cannot display smooth transitions from one color to another. Instead, you get a terrible jagged effect between colors and their tonal values.

Let me show what I mean. Here are two simple black and white gradients that I created in Photoshop. Both gradients are the same. The first was created as an 8 bit image. You see the number 8 circled in a red circle at the top of the document window, which indicates that the document is open in 8 bit mode:

But exactly the same gradient created as a 16 bit image. There are no differences, except for the fact that the name of the document contains the 16-bit mode, both gradients look the same:

See what happens when I edit them. I’m going to apply the same changes to both gradients. To begin, I will press Ctrl + L (Win) / Command + L (Mac) to invoke the Photoshop correction. Levels (Levels), and without going into details of how the levels work, I just move the bottom black and white sliders. Output values (Output) towards the center. Again, I will do this with both gradients:

Move the lower black and white Output sliders (Output) towards the center in the Levels dialog box (Levels).

Essentially, I took the full range of gradients from pure black on the left to pure white on the right and flattened them into a very small segment in the center, which eventually represents the average shades of gray. In fact, I did not change the gradient. I just concentrated his tonal range in a very small space.
Click OK to exit the dialog box. Levels (Levels), and now let’s look at the gradients again. Here is an 8 bit gradient:

And here is the 16 bit gradient:

Both gradients after correction with Levels (Levels) now look like solid gray, but they still look the same, although the upper gradient is in 8-bit mode, and the lower one is 16-bit. See what happens when I apply again. Levels (Levels) to stretch the tonal range of the gradient back to pure black on the left and to pure white on the right. I will move the black and white sliders Input values (Input) dialog box Levels (Levels) towards the center, this time to distribute the dark parts of the gradient back to pure black on the left and the light parts back to pure white to the right.

Moving Input Values ​​(Input) black and white sliders towards the center to distribute dark parts of the gradient back to pure black on the left and light parts back to pure white to the right.

Let’s look at our two gradients again. The first is an 8 bit gradient:

Ouch! Our smoothed black and white gradient no longer looks so! Instead, it has a “graded” effect, which I talked about, where you can easily see how the shades of gray are replaced one after another, and this is because we lost a huge part of the image details after performing the corrections that we did with Levels (Levels). Thus, an 8 bit image did not do a very good job. Let’s see what happened to the 16 bit image:

Look at him! Even after the big adjustments I made with Levels (Levels), 16 bit gradient coped with the task without a single blot! Why is that? Why did the 8-bit gradient lose so many details, but the 16-bit one didn’t? The answer lies in what we talked about up to this point. An 8 bit image can only contain a maximum of 256 shades of gray, while a 16 bit image can contain up to 65,536 shades of gray. Even though both gradients looked the same at the beginning, 16 thousand additional shades of gray give us more flexibility during editing and the likelihood of any problems appearing afterwards. Of course, even 16-bit images eventually reach the point where they begin to lose a lot of detail, and you will see problems after many image edits, but in 8-bit images this moment comes faster, and with a 16-bit image we can deal much longer .
Let’s try this time to look at the same things on the example of an ordinary photo.

Photo editing mode (mode) 16 bits
Let’s try the same editing experiment to apply to a full-color photo. I took a photo with a beach ball, which we saw on the first page. Here is an image in standard 8 bit mode. Again we see the number 8 at the top of the document window:

And here is the same photo, but in 16 bit mode:

Both images look the same at the moment, just like those two gradients.
The only difference between them is that the top image is 8 bit, and the bottom 16 bit image. We will try to make the same adjustments using Levels (Levels). Now I am editing an image with an extreme method, this, of course, is not what you usually do with your images. But this method will give you a clear idea of ​​how badly we can damage an image if it is in 8-bit mode compared to the minor damage that occurs when editing a 16-bit version of an image.

I press the key combination Ctrl + L (Win) / Command + L (Mac) again to open the dialog box Levels (Levels), and move the sliders Output values (Output) down towards the center, at the same point as in the case with gradients. Again, doing the same with both images: 8 bit and 16 bit versions of images:

Moving white and black Output sliders (Output) towards the center in the Levels dialog box.

Here’s what an 8 bit image looks like after concentrating the tonal range in a small space where you usually find information about middle tones:

This is how a 16 bit image looks like:

Again, both versions are identical. There are no visible differences between the 16 bit and 8 bit versions.
Now call Levels (Levels) and set the pitch values ​​back so that the dark areas become pure black and the light areas pure white:

Move the black and white slider input values ​​(Input) towards the center in the Levels dialog box to concentrate the dark parts of the image in black and the light in white.

Now let’s see if there is any difference between the 16 bit version and the 8 bit version. For a start, 8 bits:

Oh no! As with the gradient, the 8-bit image suffered quite decent damage thanks to editing. A very noticeable transition in color, especially on water, which looks like some kind of drawing effect, rather than a full-color photo. You may also notice damage on the beach ball, as well as on the sand at the bottom of the photo. At the moment, 8 bit image has brought little benefit.
Let’s see what happened with the 16 bit image:

Again, as with the gradient, the 16-bit version was left unmarked! Each bit remained the same as before editing, while the 8-bit image lost a lot of detail. And this is all because the 16-bit version has such a huge number of possible colors available. Even after the strong impact that I made, I could not inflict visible damage on the image due to the 16 bit mode.

So how can you take advantage of the 16 bit image? Simply. Always take RAW pictures instead of JPEG (of course, of course, if your camera supports raw), then open and edit it in Photoshop, as a 16-bit image. Remember that when you work with a 16-bit image, its size is larger than 8-bit image, and if you have an old computer, it can affect the duration of processing photos in Photoshop. Also, despite the fact that new versions of Photoshop are getting better and better in this regard each time, not every filter is available for image correction in 16-bit mode, but most of the basic ones work. If you want to work in 8 bit mode, go to the menu Picture (Image) at the top of the screen and select Mode (Mode) and then select 8 bits. Try to work in 16 bit mode as long as possible before switching to 8 bit mode. Also, make sure you switch to 8-bit mode before printing the image, or even save your 16-bit version of the image as a Photoshop .PSD file, and then save a separate 8-bit version for printing.

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