Histograms in Adobe Photoshop

[EmeraldHike]

Histograms are immensely helpful tools when it comes to editing photographs, but I have to say, while they look very cool to have hanging around our cameras and editing applications, they’re also one of the most ignored features out there. Personally, I feel very professional when a histogram is in view. Do I use it all the time? Sadly, I don’t. I’ve been doing this for so long now that I’ve got a feel for certain things. Histograms are definitely important though, especially for newcomers in this game. They can offer tons of useful information and they shouldn’t be ignored at all. Sometimes your eyes can fool you as you’re viewing a scene or an image. Histograms don’t fool you. We should all be using them much more often.

What is a histogram? It’s basically a tool that measures exposure in an image. I’ll leave it at that. As I continue to write this post down below, you’ll learn much more about these little treasures. What does a histogram look like? Here’s one for you. It’s from Adobe Photoshop.



I opened this Histogram panel by going to the Window > Histogram menu item and clicking. When it opened, it was stuck to the toolbar on the right. To separate it from the toolbar, I simply clicked on the top part of it and dragged it away. Now it’s sitting in the middle of my screen.

In today’s post, I’d like to do some exploration around the Histogram panel as well as explore how this tool can help when it comes to analyzing and editing photos and graphics. While this tool may seem intimidating at the beginning, once you understand exactly what it’s here for, it won’t be intimidating at all. It’s actually quite friendly.

The Different Views of the Histogram​

In the upper right corner of the panel, there’s a menu. If I click on that menu, I’ll see a few different options that pertain to how the panel is presented in Photoshop.



As you can see, I’m currently in the Expanded View, which offers a few handy statistics below the graph. There’s also the Compact View, which is smaller and which doesn’t show any statistics. There’s also the All Channels View, which shows not only the RGB histogram, but individual histograms for the Red, Green and Blue channels.



This All Channels View can come in handy when you’d like to analyze and edit specific colors in the image you’re working on.

Regenerating the Histogram​

As you work in Photoshop, data becomes cached in its memory. Because of this, the histogram you’re currently viewing may not be populated with the most up to date information. If you see a small triangle with an exclamation mark inside of it and roll over that warning symbol, you’ll see this text appear: Click for Histogram with Uncached Data. If you click that warning icon, the histogram will regenerate itself and will be once again populated with unchached, recent information.

Viewing a Histogram For Each Color​

At the top of the Expanded View histogram is the Channel drop-down box. If I click that box, I’ll see a few different options. In this section, I’d like to briefly address a few of the options available in this drop-down.



Currently, we’ve got RGB, Red, Green, Blue, Luminosity and Color options available. If I click on any one of these choices, I’ll see the histogram change in shape. Since the image I’m using as an example in this post is fairly uniform and dark in color, I’m not seeing large swings in the curve, but if I was using a different image that had many varying colors in it, I’d see much more of a difference among options.

If I select the RGB option from the drop-down, I’ll see all of the colors merged into one curve. I won’t be able to distinguish between any color’s curve in the image. If I choose either the Red, Green or Blue options, I’ll get a curve that separates out that specific color. If I choose the Luminosity option, I’ll see a histogram that represents the luminance values of the three channels combined. And finally, if I select the Color option, I’ll see each individual histogram for the red, green and blue colors overlay one another. It’s basically a composite of the three, but the individual colors are visible and easily distinguished. Personally, I like to use the Luminosity option to check the image’s overall exposure value. After all, that’s the primary use for this tool.

Viewing Luminosity For Individual Color Channels​

This is where things start to get interesting. Let’s say that I have an image that’s overexposed in a certain area, but I’m not sure where that area is. My guess is that it’s in one of the colors and I’d like to find out which one. To view each individual channel’s luminance values, I’ll change the Histogram panel’s view to All Channels View and then I’ll select Luminosity from the Channels drop-down. Here’s a trimmed screenshot of this setup.



Now, if I wanted to adjust the luminance of just one channel and see if it’s making a difference in that particular luminosity histogram, I could easily add a Levels adjustment layer to the image from the Adjustments panel and then set the value to Red, if that was, for example, the color I’m interested in altering. Take a look. This next screenshot is of just the histogram I previously showed you above sitting to the left of the Levels adjustment layer Properties panel. Notice how I’ve set the Levels drop-down to Red.



I also went ahead and pushed the right handle in the Levels adjustment layer Properties panel to the left, which brought out a lot more red in the image. As I did this, I watched the Red curve in the Histogram panel move in conjunction with the changes I was making. It’s all very interesting and rather helpful. It’s a granular approach to editing photographs.

As you can see, the Histogram panel inside of Adobe Photoshop can offer tons of valuable information. When combined with other tools in Photoshop, it can be a handy guide that can assist with properly editing a photograph or graphic. If you have any questions regarding this tool or specific panel, please let me know in the comment section below or in the Photoshop discussion forum. Thanks for reading!

 

[EmeraldHike]

Using the Histogram in Adobe Photoshop to Easily Make Color & Exposure Edits​

I was reading through a post that was recently written on this blog that discussed the many different options available in the Histogram panel in Adobe Photoshop and was inspired to take things a few steps further than that post in this one. Basically, I’d like to talk about how you can use the various histograms in the All Channels View of the Histogram panel to assist you when making exposure and color choices. Typically, editors (people) will take advantage of the various available adjustment layers in the Adjustments panel to modify the look of an image and I wanted to offer a few examples of how these adjustments can be used alongside the histograms. Since the Levels adjustment was already covered in the post, I figured I’d move on with the Curves adjustment. So, to follow along, go ahead and open up an image in Photoshop and apply the Curves adjustment to it. Then, make sure the Histogram panel is opened up and undocked, so it’s floating around your workspace. That’s the easiest way to view both panels simultaneously. What you should see is something like this:



As a reminder, the Histogram panel doesn’t actually do anything. It merely displays the information you’ll need to do that something with a different tool. In this case, the tool we’ll use is the Curves adjustment. So what we’ve got here is the Histogram panel in the All Channels View on the left and the Properties panel for the Curves adjustment on the right. Having this clear view of both panels is the reason I suggested undocking the Histogram panel above.

In today’s post, I’ll be simply adjusting the colors of the image via the individual color channels. To start off with, I’ll keep the Channels drop-down in the Properties panel set to RGB. I’ll then give the center of the curve a click and drag downward a bit, just to get an idea of what that not only does to the image, but to the three color histograms as well. Here’s the screenshot of that.



Do you see how that one adjustment affected all of the histograms? I know you can’t see the bottom two (Green and Blue), so you’ll have to trust me that they moved. The photo was also darkened overall.

In the next example, I’ll set the Channels drop-down in the Properties panel to Red. I’ll then click and drag the curve up a hair. Let’s see what that does to the Red histogram.



If you compare the Red histogram on the left in this most recent screenshot with the one in the previous screenshot, you’ll see how it changed. Basically, taking advantage of the various elements of the Histogram panel can help out a lot when it comes to correcting the color and exposure of an image because it can give you more information than you’d have otherwise. And the best part is, the histograms can be used in conjunction with many different adjustment layers, not only the Curves one I used today in this example.

Do you have anything to add to this post or any questions regarding histograms or adjustment layers in Adobe Photoshop? If so, please add them below. Thank you.