Photoshop is a pretty daunting program when you’re beginning. So this is the first in a series of articles to bring you up to speed on some of the most useful tools to you as a photographer for editing and correcting your photos. If you’ve been a Lightroom only user, and are a CC subscriber, do follow along to start your journey into Photoshop. In this article, you’ll learn how to use the Levels tool, along with Auto Levels and learn to set up Auto Levels to suit your personal preference for the tool’s response.
You’ll also take your first step with Layers by using a Levels Adjustment Layer right at the end. But first, we’ll talk a little about Histograms.
A Histogram is a graphical representation of the colors and tones in your photo. The bottom axis shows the range of brightness in the image from dark to light. The side axis shows the strength a given tone has at that particular brightness. Typically you’ll hear people say that the bulk of tones should be in the middle, but that’s not exactly right. A night scene of stars will have the bulk of the tones in the dark region, with a spike at the top. Same for a dark product shot on a white background.
Histogram of a high key (light) image.
High Key shots will tend to have more information on the right of the histogram, while low key portraits will have them mostly to the left.
In general, most images will have information throughout the range of tones. When they don’t, but should, that’s where the levels tool comes into play.
To begin, you can use the keyboard shortcut CNTL/CMD+L, or choose Levels from the Image>Adjustments Menu. This is a destructive version of the tool, so it will throw away pixels. You won’t be saving this file, so it’s okay for now.
I’m using an image that I know is underexposed (you can tell by the histogram below as it doesn’t touch the right-hand side of the graph). Let’s look at what’s in your Levels tool dialog.
You can save settings as a preset to reuse again quicker, there are a few default ones that ship with Photoshop. You can choose these presets and see both the effect and what’s been done to get it.
Level presets that come with Photoshop.
As well as the overall tone channel (RGB), you can select the red, green or blue channels separately. This will change the color balance of the image and you can use it to fix white balance issues or to creatively manipulate the look of the photo. For now, you’ll just be using the RGB channel.
This shows the histogram with three triangles (see above). Each triangle has a number below it (the defaults are set at 0, 1.00 and 255). You can edit these points by dragging the triangle along the histogram. They have names too. The leftmost is the Black Point, which controls the darkest tones in the image. The centre one in the Mid-tone Point, while the top is the White Point, or brightest tone in the image.
If you move the Black Point to the right, all tones to the left of the new position are rendered as pure black pixels. If you move the White Point to the left, this means that any pixel to the right of the new position will be rendered as white. Moving the Midpoint, (also referred to as the Gamma) it will shift the histogram the same direction effectively lightening or darkening the mid-tones. Left will lighten the mid-tone, while moving it to the right will darken. You may also have a perceived change in contrast as some tones at the extremes are compressed.
You can dictate the brightest or darkest point allowable in the image using these sliders. In general, you won’t use these as much as input levels.
OK applies the Levels change. Cancel ignores any changes. We’ll look at Auto and Options separately. The Eyedroppers allow you to select the Black, Mid-tone, and White Points by clicking on specific parts of the photo. Preview allows you to see the changes you’re making on the image before applying the effect.
Now that you know what the bits do, let’s look at them practically. You can see there’s a huge gap between the ends of the mountain in the histogram below and the White Point slider. By moving the White Point to the left, you can brighten the image and fix the underexposure.
Original histogram – notice the gap between the end of the mountain and the right-side of the chart? This indicates underexposure and is easily fixed.
Here the White Point has been moved to the left to touch the bottom of the mountain. This will give the image brighter tones and pure white.
By holding the Alt/Option key as you slide, you also see a heat map that shows where and clipping (pure white with no detail) occurs. For the White Point, the screen goes black, and the clipped areas show as color. For the Black Point, the image goes white, and again, the clipped areas show as color.
Holding Alt/Option while moving the slider, you can see there are some areas being clipped in the highlights. Move the White Point slider back to the right until they disappear in order to have detail in all areas of your highlights.
Here’s the result:
If your image is overexposed (but without the highlights clipping in important areas), you need to do the opposite. In this case, you bring the Black Point up to fix the issue.
See the different left to right here? There is no black in the image on the left.
Another possibility is the detail is all in the middle of the histogram (low contrast or flat image). In this case, you need to move the sliders in from both ends. Notice the increase in contrast between the two photos.
By moving the Black Point to the right and the White Point to the left the contrast has been increased in this image.
While you’ve seen what changing the black and white points can do, you should also know that moving the midpoint will allow you to brighten (by moving to the left), or darken (by moving to the right) the mid-tones in your photo.
Auto Levels, as the name suggest, will do this for you automatically. How Auto Levels responds depends on the settings in the Options section. These have changed with time as well, so you may not be aware of this. Press Auto Levels for this to work.
After Auto Levels has been applied.
To change the Auto Levels default settings you use the Options button.
Enhance Brightness and Contrast
The default option is Enhance Brightness and Contrast, which uses the external Brightness and Contrast tool to get a good rendition of the file. This is the look in the version of the photo above.
Enhance Monochromatic Contrast
The top option, Enhance Monochromatic Contrast is closer to what you’ve done manually in the previous section. Here’s what it looks like (starting from a fresh version of the file). First the settings in Options.
This results in the following, more dramatic, look.
Auto Levels with the default set to Enhance Monochromatic Contrast.
You can also automatically fix the color by clicking the “Snap Neutral Midtones” checkbox.
You’ll notice that the shadows are more than a little crushed in these images, though. That’s because of the mix of the swatch settings and the clip settings below. Clicking on the swatch gives Photoshop the base color for your blacks, neutrals, and white. In general, these should be black, mid gray, and white, but you could set them to suit tasks like having pure white below 255 to render something when printed, instead of paper white. For now, you should leave these at the defaults.
To prevent pure white and pure blacks being so deep, you need to back off the clipping settings. Put them at 0%.
You’ll notice the reduction in the blacks from this adjustment immediately. If you prefer the drama, leave the black clipping at 0.10%.
You can have your images render this way automatically by ticking the “Save as Defaults” checkbox.
Enhance Per Channel Contrast
This setting emulates you going in and setting each channel separately to get the white and black points to the edge of information for each color channel.
This has the effect of changing both the contrast and the color of your photo as seen below.
Find Light & Dark Colors
This option is used by the Auto Color command. It finds the average lightest and darkest pixels in your photo and uses them to get the best contrast while avoiding clipping.
Each person will have their own preference for which looks best on their photo. So choose the option you prefer the most and save it as the default. Now when you use Auto Levels, it’ll give you a quick fix when you need to get done in a hurry.
Levels Adjustment Layer
Everything you’ve done so far has been destructive editing. You’ve been throwing away pixels, which affects the quality of the photo. Have a look at the histogram in Levels when using the Enhance Monochromatic Contrast option.
See all those gaps? That’s information you’ve thrown away. If you change your mind, you’ve got nowhere to go, you can’t get that information back. There are ways to prevent this of course. You could, for instance, duplicate the layer (CTRL/CMD+J) and work on that. But you have an even better option; the Levels Adjustment Layer.
At the bottom of the Layers panel is the Adjustment Layers option. It’s a circle that’s half black and half white.
Click this to bring up the available Adjustment Layers and choose Levels. (Note: you can also open the Adjustments panel by going to: Window>Adjustments and then find the levels option, it’s the one that looks like a graph right after the sun icon).
The Adjustments panel – Levels is the second one on the top row.
A new layer, called Levels, will appear in your Layers panel. The controls for Levels don’t show as a dialog, they’re now in your Properties panel.
If you can’t see the Layers or Properties panel, you can turn them on in the Window menu. Using the Properties panel, set your Levels. If you’re not happy you can just change the settings as often as you like, without degrading the image like repeated use of the normal Levels tool would.
For the plane photo, I used Auto, which had Enhance Monochromatic Contrast, with 0% clipping, and Snap Neutral Midtones on, as the Default. I then brightened the image using the Midtone, set to 1.15.
Right folks, so that’s been a look at the Levels tool in Photoshop. It’s one of the most fundamental photo tools in Photoshop. I actually think it’s a shame that Lightroom doesn’t have equivalent options in the Basic panel that emulate the options available in the Auto options (Aperture had buttons for both Monochromatic and Per Channel Auto Levels for example).
Give the tool a try, especially if you’re just starting to come to grips with Photoshop.
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Author: Sean McCormack
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