It’s somewhat ironic that in this age in which we have become so obsessed with the performance of our cameras and lenses that we continue to use 8-bit color depth when working with the images in our computers.
If you have purchased the latest camera or lens for your photography, I assume you made the decision at least in part with the idea that you were getting the latest and greatest gear. That’s all well and good but if you turn around and edit your files in 8-bit, you’re tossing quality out the window with every edit. This is especially bad if you shoot in jpeg instead of RAW. At least if you shoot in RAW you have opportunity to make edits to your images at a higher bit depth when you process your RAW images.
A counter argument to this is that an overwhelming majority of devices out there are 8-bit, so there’s little point in using 16-bit. While it is true that most devices are 8-bit your EDITING is best done in 16-bit. This is because an 8-bit image just happens to be the bare minimum before our eyes start to become blatantly aware of image degradation. So, if you adjust your exposure in 8-bit you are lowering the detail in the image below the threshold necessary for our eyes.
There are a couple of ways to demonstrate this effect. First, I will take a slightly underexposed image and adjust the exposure in Photoshop.
In the first image is the version that was edited as a 16-bit file, you can see that the histogram is nice and smooth.
In the second image below is the version that was edited as at 8-bit color depth. Again, all I did was adjust the exposure slightly. You can see in this histogram that there are vertical dark lines, those dark lines are actually gaps in information. Yes, there is literally information missing in the edited 8-bit image.
It’s important to note that gaps in information occur when editing the 16-bit file as well. The difference is those gaps aren’t as apparent because there is so much more information present in the 16-bit file. In fact, an 8-bit image allows for 256 levels of brightness while a 16-bit image allows for 65,536 levels of brightness. Which just so happens to be 256 times more information (256 * 256 = 65,536).
Basically what it means to you is that if you edit in 16-bit you can freely adjust things like exposure and levels without worrying about extensively degrading your final output image.
For instance in the following images I will edit a gradient in 8-bit and 16-bit using the levels tool. Just look at what happens.
In the first image I take a gradient and using the levels tool I compress the output levels, apply the effect, then run levels again and use the input levels to expand the image back. As you can see the gradient is still pretty smooth in the 16-bit edit below.
I saved what I did with the levels as an action and ran the action on an 8-bit version of the gradient, below is the result.
As you can see the 16-bit image has a huge amount of overhead that will allow you to make all the edits you need and still end up with a great looking image.
Most cameras don’t use 16-bits per channel for RAW files, they’re typically in the 10-bit to 12-bit range. So you might be wondering if it is ok to use 8-bit if your camera only support 10-bit RAW files. The answer is quite simply no it is not OK! Just understand the following, while an 8-bit image allows 16.7 million colors, going to 10-bits allows for 1.07 BILLION colors. Yep, 2 extra bits add 984 million colors.
The information is there you might as well use it! Again, this isn’t about whether you can see 16-bits of color, it’s about avoiding image quality degradation when you go to print or when you save to an 8-bit JPG. It’s really just common sense. You shouldn’t edit in the same low quality color depth that you’re going to output to.
How to use 16-bit color depth
If you’re wondering how to use 16-bit color depth, you’re in luck because I’m about to tell you. When you open your RAW files in Photoshop ACR simply click the button at the bottom of the window (highlighted in red) a window will popup, in the “depth” menu choose the 16-bit option. This will cause Photoshop to open the file in 16-bit mode when you’re done processing the RAW file.
Do you use 16-bit color in your edits? Let us know your thoughts in the comments below.