Start learning with our library of video tutorials taught by experts. Get started

Photoshop CS6 Quick Start for Photographers

Bit depth


From:

Photoshop CS6 Quick Start for Photographers

with Tim Grey

Video: Bit depth

I assure you there was no pun intended when I decided to use this image of a whale diving deep into the waters off Alaska to discuss the issue of bit depth. Bit depth has nothing to do with depth in the way you might normally think of it, but rather the number of colors actually available for an image. Generally speaking, you have two options for bit depth, the 8 bit per channel mode and the 16 bit per channel mode. A bit is a value used by a computer which essentially means on or off. It's often described as the ones and zeroes of data, because those values, on or off, are often described as being a one or a zero, effectively a yes or a no. If we have eight bits, and each bit can have two possible values, essentially one or zero, that means that there are 256 possible tonal values per channel. I'll go ahead and open up the channels panel, and we'll take a look for example at the red channel.

Watch this entire course now—plus get access to every course in the library. Each course includes high-quality videos taught by expert instructors.

Become a member
Please wait...
Photoshop CS6 Quick Start for Photographers
2h 14m Beginner Apr 23, 2012

Viewers: in countries Watching now:

Often photographers who want to learn to use Adobe Photoshop just dive in and figure out how to do what they need to do. This is all well and good, but with this approach you're likely to miss out on features that could help you, ways of working more efficiently, and an overall understanding of how Photoshop works. In this course Tim Grey takes you systematically through Photoshop's interface and tools, then shows you how to make basic adjustments and output your work for sharing. Whether you've been using Photoshop for a little while or you're just getting started, this workshop will make sure you always know where you are and where you're headed.

Topics include:
  • A guided tour of Photoshop
  • Setting up your environment
  • Color modes, bit depth, and image resolution
  • The Histogram
  • File formats
  • Basic adjustments
  • Saving
  • Output workflow
Subjects:
Photography video2brain
Software:
Photoshop
Author:
Tim Grey

Bit depth

I assure you there was no pun intended when I decided to use this image of a whale diving deep into the waters off Alaska to discuss the issue of bit depth. Bit depth has nothing to do with depth in the way you might normally think of it, but rather the number of colors actually available for an image. Generally speaking, you have two options for bit depth, the 8 bit per channel mode and the 16 bit per channel mode. A bit is a value used by a computer which essentially means on or off. It's often described as the ones and zeroes of data, because those values, on or off, are often described as being a one or a zero, effectively a yes or a no. If we have eight bits, and each bit can have two possible values, essentially one or zero, that means that there are 256 possible tonal values per channel. I'll go ahead and open up the channels panel, and we'll take a look for example at the red channel.

There are 256 possible shades of gray here If we were working on an 8-bit-per-channel image. And that's because each bit can have two possible values. And there are 8 bits for each channel for each pixel. So 2 taken to the eighth power equals 256. 2 times 2 times 2 repeated 8 times gives you 256. But of course, we're working with an RGB image, so there are three channels, red, green, and blue. That means that we have to take the 256 tonal values available per channel and multiply it by itself, three times.

In other words. to cube that 256 value. 256 cubed equals over 16.7 million possible color values. And it just so happens that 16.7 million is the number of colors believed to be how many the human visual system can discern. And that's a lot. So why would we ever take advantage of this 16-bit per channel mode? First, let's consider how many colors we might have available in that 16-bit per channel mode. To start with, each of the individual channels in a 16-bit per channel mode can have a large number of possible tonal values.

It's two raised to the 16th powers. So two times two times two, a total of 16 times. The result is sixty five thousand five hundred and thirty six possible tonal values per channel. That's quite a lot, and those numbers get even bigger when you remember that we have three channels to contend with. So, we have to take 65,536 and cube it. When we calculate 65,536 cubed, the result is over 281 trillion possible colors.

That's a big number. A very big number. And in some ways you can appreciate, I'm sure, that that's a bit of a theoretical number. Because you're not really going to produce that many colors in most images. In fact, Photoshop generally calculates numbers based on 15 bits per channel. And furthermore, your camera is probably not recording 16-bit per channel information. Many cameras record analog to digital information at 12 bits per channel, with most current cameras converting at 14 bits per channel. Still, some cameras do indeed capture at 16-bit per channel.

But when you convert that raw capture data, you need to put it in either in an 8-bit per channel or 16-bit per channel package. So if your camera is 12-bit or 14-bit, the image is still going to be a 16-bit per channel image, by default, even though it contains less than that full range of possible values. So why would you work in the 16-bit per channel mode? First and foremost, it has to do with detail and image quality. Because we have so many more values available to us and so many more tonal and color values for our pixels, there's a broader range available. And therefore, we can apply stronger adjustments without reducing the level of detail in a photo.

Every adjustment you apply to an image causes some loss of information, you can appreciate this by thinking of a strong contrast adjustment, for example. With a strong contrast adjustment an 8-bit per channel image might start to show some posterization, whereas a 16-bit per channel image might not. Of course, in many cases, because of the way our monitor displays work, it's very difficult to see the actual difference. But I can show you what posterization looks like. I'll go ahead and add a Posterize Adjustment layer. And you can see here posterization, A very harsh transition between tonal and color values.

A photographic image generally has very smooth gradations. But as we reduce the range of color and tonal values, and apply strong adjustments, we start to see posterization, and that can obviously be a problem. Working in the 16-bit per channel mode helps preserve as much information as possible so you won't run the risk of posterization. That said, there's really no benefit to choosing Image, Mode, and then changing an 8-bit per channel image to 16-bit per channel. If you didn't have the information to start with, you're not going to get any real benefit by converting the image to 16-bit per channel.

I do recommend converting your raw captures to 16 bit per channel. And continuing to keep those images in the 16 bit per channel mode while you're working on them. It does create a larger file size, but I think it's worth it in terms of helping to make sure you're going to retain maximum detail and quality in all of your photos.

There are currently no FAQs about Photoshop CS6 Quick Start for Photographers.

Share a link to this course
Please wait... Please wait...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.
Upgrade now


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ.

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Upgrade now

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed Photoshop CS6 Quick Start for Photographers.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferencesfrom the dropdown menu.

Continue to classic layout Stay on new layout
Welcome to the redesigned course page.

We’ve moved some things around, and now you can



Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked