File Basics: Bit Depth
by Jeff Lazell – August 4th, 2014
Welcome to File Basics, a new feature to the X-Rite blog where I hope to demystify a lot of the settings and terms associated with building an effective post processing workflow. I worked on the production side of the photo industry for almost a decade and I know that focused, succinct explanations are not only the best way to learn, but can sometimes get you out of a sticky situation. Today I would like to begin with bit depth.
When processing your Raw files you have to make several choices that will have a profound effect on your file’s quality. These choices will follow you through the rest of the workflow, so making educated ones is paramount. One of the biggest choices is what the bit depth of the file you are going to output to is: 8 or 16-bit. Now, the difference between these two options is the number of shades from light to dark on each color channel, red, green and blue. For instance, an 8-bit file has 256 shades on each of these channels for you to work with.
Logically this would lead some to think that a 16-bit file has 512 shades on each channel. However, the naming convention actually deals with exponents. Meaning, 8-bit files have 256 shades because we are in reality talking about “2 to the 8th power”. So, following that a 16-bit file is actually referring to “2 to the 16th power”. Thus giving us a file with 65 thousand 5 hundred and 36 shades per channel.
Clearly 16-bit is the choice for any file you plan on editing. Even though many labs and printers require you to down mix to an 8-bit file. The reasoning behind this is that every edit you do to a file causes these shades to break down. Do this enough and you will be left without enough data for smooth gradations. Things get a bit blocky and bands of color appear, something I am sure we have all seen especially in what were once nice sky tones.
So, if you start with a 16-bit file to work on you have a ton more shades to work with. Even if you do some crazy editing and you lose 80% of your data you will still be left with over 13 thousand shades when its time to down mix for print. Also, now most high end photo inkjet printers have the option to receive 16bit files, eliminating the need to down mix before printing. Just a note here. If you are capturing in Jpeg due to an equipment constriction or simply because you are not comfortable shooting in RAW, the option for a 16-bit file will not be open to you. Jpegs will always be only 8-bit due to the compressed nature of the file format. So, this is another great reason to move up to capturing in RAW. I hope you find this information useful when setting up your own post processing workflow, if you have any questions please post them below. If I get enough questions about one topic I will turn to the answer into an article like this one. I hope that with the help of the readers of this blog I can create a good resource for photographers and production artists.
Learn how you can stop guessing and start knowing with color management solutions from X-Rite at www.xritephoto.com.