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To change the gridline increment, Alt-click (Windows) or Option-click (Mac OS) the grid.
Once the correction is complete, the sample points are removable by holding down Ctrl + Alt (Cmd + Option) keys and clicking on them. You should see the scissor icon when you hold these keys down. To finish, either save the image with its adjustment layer intact or flatten the layers, as required.
Repeat this procedure with a neutral gray mid-tone, if you can find one, with RGB values of around 120-140.
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This is the color-corrected image. With the blue cast gone, other colors in the photo can breathe. In particular, the yellow color of the hotel and the green in the grass and trees are more prominent.
Let’s see what happens when we add more points to the curve. Go ahead and repeat the process we performed above to select one the lightest points in your photo (like our espresso cup) and then pick darkest point using the same technique. You’ll end up with a dot for the light and a dot for the dark on your curve.
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When working with curves, histograms, and RGB numbers, it’s useful to know what the histogram is telling you. There’s no such thing as a right or wrong histogram, per se, since it only mirrors the pixel data of the image, but it will highlight potential problems.
Holding down Ctrl + Shift (Cmd + Shift in Mac) and clicking with the eyedropper tool places a sample point on each of the three RGB curves. This is useful for adjusting specific mid-tones. Here, I’ve opened the red channel to illustrate this. To correct color, you have to adjust the individual red, green and blue channels until the corresponding output numbers on the info palette match.
Choosing Image > Adjustments > Curves applies the adjustment directly to the image layer and discards image information.
To deselect all points on the curve, click in the grid, or press Ctrl‑D (Windows) or Command-D (Mac OS).
Light (0-255) Displays the intensity values for RGB images in a range from 0 to 255, with black (0) at the lower-left corner. Pigment/Ink % Displays the percentages for CMYK images are displayed in a range from 0 to 100, with highlights (0%) at the lower-left corner. Simple Grid Displays gridlines in 25% increments. Detailed Grid Displays gridlines in 10% increments. Show Channel Overlays Displays color channel curves superimposed on the composite curve. Histogram Displays a histogram of the original image tonal values behind the graph. Baseline Displays the original image color and tonality as a 45-degree angle line for reference, Intersection Line Displays horizontal and vertical lines to help you align control points as your drag them relative to the histogram or grid.
(Curves dialog box) To set a point on the curve for the current channel, Ctrl-click (Windows) or Command-click (Mac OS) in the image.
In this black and white RGB image, you can see that the red, green and blue histograms are identical. You won’t get this in a color photo, but if the histograms look similar, especially from the middle to the right-hand side, there is unlikely to be a noticeable color cast.
Here you’ll see that all three sets of RGB values have been equalized – for each point, you see the before (left) and after the (right) value (Red on point #1 went from 238 to 239, Blue from 244 to 239).
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The types of correction discussed in this article work best when there are naturally occurring color casts in the image. In mixed lighting, where the light sources are radically different (e.g. incandescent lighting and daylight), you’ll need to painstakingly address each affected area of the image using layers in Photoshop or the adjustment brush in Lightroom. Avoid this type of lighting wherever possible, since it’s difficult and time-consuming to correct in processing.
If you’re instead using the Curves adjustment, simply click in the image with the On-image adjustment tool .
Just like our previous photo tutorial, you will need two basic things:
If you were worried that we had run out of fun tricks in the Curves menu, well, worry no more. We have another handy little trick to help you manipulate the curves and further enhance your black and white images. There’s a big part of the Curves menu pane we haven’t even talked about yet, and that’s the black, gray, and white adjustment droppers at the bottom of the pane.
Our work with black and white images makes these tools even more relevant. When we want to create high contrast images and really capture the crispness common in old black and white photos, it’s so easy to do so with a quick manipulation of the black, gray, and white points. Click on each one and select the darkest point in the image, a mid-tone gray point, and the whitest point in the image:
Here, we’re creating a mid-tone sample point. Again, you can see from the numbers (RGB 111, 120, 137) that there’s a strong blue presence. The highlight sample point that I’ve only just recorded is stored on the depicted info palette at the left, third down (marked as #1).
Usually, it’s best to choose the lowest or middle of the three existing highlight values and match the other two to that (see “tip” below).
Before you start in curves, there are a couple of things you’ll need to prepare in Photoshop:
Hold down Alt (Windows) or Option (Mac OS). Choose Show Clipping For Black/White Points from the panel menu.
Whenever a photo contains an area that should be neutral gray in your estimation, you can use the mid-tone eyedropper tool in either levels or curves to quickly correct any color cast. Simply clicking on the supposedly gray portion of the image will correct the color. It’s usually worth clicking a few times in different areas until you achieve a result that pleases you. There are ways of calculating precise mid-tones in an image to make this method more precise, but guessing often works well and is far quicker.
Click directly on the curve line and then drag the control point to adjust a tonal area. Select the On-image adjustment tool and then drag in the area of the image you want to adjust. Select the On-image adjustment tool and click the tonal areas in the image that you want to adjust.
This places control points along the curve line. Choose a preset from the Preset menu.
To preview clipping as you adjust black and white points, do one of the following:
Photos to edit Adobe Photoshop We’ll be using a copy of Adobe Photoshop CS6, but the techniques outlined in today’s tutorial should work just fine in previous editions of Photoshop, as the tools we’re using have been included in Photoshop for years.
For today’s tutorial, we’ll be using a simple photo we snapped of our morning espresso splashing down into the cup. It’s no sweeping view of Yosemite National Park, we know, but we like using low-key photos to showcase techniques because it puts more of a focus on the subtle changes of the technique itself.
We’re going to pick up where we left off in our previous photo tutorial. You have a photo you want to edit, you already converted it to black and white using one of the effective techniques we outlined, and now you’re ready to do some more tweaking.
We took our base image, seen above, and used the default filter in the Black & White adjustment menu to create a fairly neutral black and white base image. We’ll build on that below. What Are Curves and How Can I Take Advantage of Them?
Repeat this process with the mid-tone and shadow points, so that all of the chosen neutral points in the image are in fact neutral. The bottom-left shadow point is also moved along the outer edge of the graph, either upwards or right. The mid-tone point you’ll drag either up or down. If the color looks wayward at the end of this process, it typically means that you’ve picked a sample point that wasn’t neutral. Ensure that your sample points contain no color noise or reflected color. Zoom in on the area you sample to make certain of this.
This is where things get fun. We’ve just made an anchor point for the darkest and lightest parts of our image, Let’s get a little crazy with everything in between. Use the dropper tool to pick any portion of the image you’d like to adjust (or, since we’re being playful, just grab any point on the line) and make an adjustment. If you like it, leave it. If you don’t like it, slide it back into place. Feel free to tug and pull the curve as you see fit to create the image you’re looking for. After a moment or two of playing this is what we came up with:
By introducing the info palette into the equation, you can make far more precise color corrections. The technique you’re about to learn also teaches you to evaluate and edit photos by the numbers. Think about this – when you have nothing to compare an image to—no alternative version—it often looks “okay” at first glance. By studying the RGB values, you’ll get a clear idea of any potential problems in the photo.
Correcting color in images is about removing unwanted color casts. The “unwanted” part is important because some color casts are desirable. For instance, you wouldn’t want to neutralize the warm hue of a sunset. However, you might want to remove the blue color cast that sometimes pervades photos taken on overcast days or in hazy conditions. By removing an unwanted color cast, you’ll reveal the true color of the objects and subjects in your photo and make the image “pop”.
This is a picture of a hotel in Switzerland before any color correction. There is no strong color cast, but you might detect its cool bias.
For example, in the last image of the previous section of the tutorial, we arrived at a pretty high-contrast image. The whites and highlights were fairly bright and the shadows were quite rich. Since we’ve established that we like high contrast images, the next time we go to use the Curves tool, we can pre-seed our image curve by selecting “Strong Contrast”. Let’s look at the curve it gives us for that preset:
We couldn’t drop it all the way down because that would turn the picture almost completely black. Instead, we dropped it significantly below the starting line (the light gray line indicating the original baseline curve). You can see how it significantly darkens the photo and turns what was a bright coffee shop photo into something moodier. Clearly, the end result is a bit on the underexposed side, but we wanted you to see how dramatically a fairly small adjustment in the curve could change things.
In the Curves Display Options dialog box, select any of the following:
If you chose Image > Adjustments > Curves, expand the Curve Display Options in the Curves dialog box.
You can save Curves adjustment settings as presets. See Save adjustment settings and Reapply adjustment settings.
Now all points are roughly similar, in other words, all the sample points I took that were estimated to be neutral have been made neutral. Note that the numbers don’t have to match perfectly like this as long as they’re close. In the curves graph, the red channel has been lifted and the blue channel pulled down slightly as a result of my edits. The green channel was untouched in this instance, so the corresponding line cuts straight through the middle.
Clicking the On-image adjustment tool in the image adds control points to the curve. Moving the control points adjusts the tonality of the image.
In the Curves adjustment, you adjust points throughout an image’s tonal range. Initially, the image’s tonality is represented as a straight diagonal line on a graph. When adjusting an RGB image, the upper-right area of the graph represents the highlights and the lower-left area represents the shadows. The horizontal axis of the graph represents the input levels (original image values) and the vertical axis represents the output levels (new adjusted values). As you add control points to the line and move them, the shape of the curve changes, reflecting your image adjustments. The steeper sections of the curve represent areas of higher contrast while flatter sections represent areas of lower contrast.
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Drag the control point off the graph. Select the control point and press Delete. Ctrl-click (Windows) or Command-click (Mac OS) the control point.
Hovering the eyedropper tool over diffuse white highlights, I can see the blue channel has consistently higher numbers than red or green. The difference isn’t drastic, but it does indicate a blue color cast.
The values for that particular tone as well as the entire curve have been changed. The previously slightly gray cup is now shockingly white and the highlights on the chrome of the espresso machine are much brighter (as is the rest of the image). There are some nice subtle changes to the image, such as in the reflections, and the shape of the Bakelite handle of the espresso portafilter is significantly better defined against the background now. It’s not a bad looking little image, and it’s a lot more visually interesting now than it was before.
By opening curves or levels and clicking on the stone using the middle eyedropper, the magenta cast is corrected. As a result, the green in the photo is stronger.
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Open a curves adjustment layer. Hold down the Ctrl and Shift (Cmd + Shift) keys and click once again exactly on the center of the second, mid-tone sample point you created (#2). This has the effect of placing a mid-tone point along each of the individual RGB curves.
(Optional) To adjust the color balance, in the Properties panel, choose the channel you want to adjust from the menu to the left of the Auto button.
This is an exaggerated example of a curves highlight adjustment in the blue channel. I’ve pulled the highlight point to the left, which has added blue to the image (far too much blue). Moving the point down the right-hand side of the graph would increase yellow. In reality, these edits will usually be very slight, moving only a small amount either way. The info palette will reflect these changes in the RGB output numbers.
To set a point on the curve for the selected color in each color component channel (but not in the composite channel), Shift+Ctrl-click (Windows) or Shift+Command-click (Mac OS) in the image.
Drag the black and white point sliders to any point along the horizontal axis. Note that the Input value changes as your drag.
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One of the most powerful Photoshop tools at your disposal is Curves. Though it’s often only used to tweak contrast, the curves tool is also hugely effective in correcting color. What’s more, learning how to use it gives you a greater knowledge of image editing in general. It’ll enhance your understanding of the histogram and teach you how to edit photos by numbers.
The preset is essentially the curve we had in our prior image (except a bit smoother as it doesn’t have the extra pull on the highlights and lowlights that we put in). You can see how using the presents to jump in the direction you want to go and then finishing the job by making subtle changes to the existing curve is a much faster way to achieve the results you want than reinventing the wheel.
If you’re new to reverse engineering modern digital camera photos into black and white ones, we would suggest checking out previous tutorial, How to Convert Your Color Photos to Stunning Black and White Prints, first. In the introduction to that tutorial, we cover the over-arching motives for using advanced photo editing techniques to create great black and white prints.
Dragging a control point up or down lightens or darkens the tonal area you’re adjusting. Dragging a control point left or right increases or decreases the contrast. You can add up to 14 control points to the curve. To remove a control point, drag it off the graph. As you adjust the tonality, the graph continues displaying the original diagonal baseline and image histogram as references. These options can be turned off, see Set Curves Display Options.
Hold down the Shift key and click to create a sample point from this white area, which will show in the info palette as #1. It’s possible to move a sample point after you’ve created it by holding down the Shift key and dragging.
Merely hovering the eyedropper tool over a picture while watching the numbers will tell you something about it. If there are no naturally occurring “neutrals” in the photo and you want consistent or accurate color, a high-quality gray card provides a solution.
Now that we’ve played with a single point on the curve and seen how it affects everything, let’s reset the curve. Hold down the ALT key and the “Cancel” button in the Curves box will turn into “Reset”. Click to reset the curve back to the state it was in when you opened the menu.
A shadow sample point from the trash bag records at RGB 20, 21, 29. We can see now that a cold color cast runs through the entire image from highlights to shadows. Once I’ve clicked on this, my three sample points are all stored and displayed in the info palette.
We recommend manually playing with the Curves tool for a while until you get a real sense of how changing the curve changes your images. Once you’ve done that, however, you’ll likely find it invaluable to call on the Curve tool presets.
By dragging the eyedropper tool over this gravestone, we can see that the green value is less than that of red or blue. We might reasonably expect this stone to have a neutral gray color, which would give roughly equal RGB values, but the green deficit (RGB 160, 149, 160) indicates a magenta (opposite of green) cast.
Before you proceed, it’s important to note that an image always needs “neutral” areas for color correction to succeed. That’s because a neutral tone provides a known reference point that you can work from. Neutral pixels always have identical RGB values (e.g. 128, 128, 128). Any photo that doesn’t contain a neutral tone is difficult to accurately correct. This is true whether you’re adjusting color yourself or hitting an auto-color-correct button. Photographers often use gray cards to introduce a known neutral into the image for color correction later.
In the image above, you can see both the base photo and the unadjusted Curves readout of the image. Notice how the line from the lower left to the upper right is a nice clean, straight, diagonal line; our Curves, in other words, are pretty flat. The curves can seem a bit abstract, so let’s pick a spot on our photo and see where it falls on the curve. We’re going to click on the white side of the cup to sample that spot. Note: If you just click a spot and hold it, it will show you the spot on the curve, but if you hold CTRL and click it then there will be a permanent mark on the curve line:
Now it’s time to correct the color cast. On a curves graph, the top right point represents highlights and the lower left shadows. In between are any mid-tone points that you placed on the curve.
The Curves adjustment can also be applied to CMYK, LAB, or Grayscale images. For CMYK images, the graph displays percentages of ink/pigment. For LAB and Grayscale images, the graph displays light values.
By looking at all three RGB (red, green and blue) histograms at once, you can immediately get an idea of whether or not the image has a color cast. If there’s no color cast, the three histograms will look very similar. A black and white RGB image illustrates this perfectly because it’s completely neutral. In that case, the three RGB values will be equal in every part of the image and the histograms are identical.
(Optional) Do any of the following to modify the adjustment:
You can control the curve grid display using the Curve display options.
Hover the eyedropper tool over a diffuse white highlight in the photo with RGB values in the 230s or 240s (try to avoid high 250 values). Use the info palette to see these values.
You can see how, in playing with the curves, it’s possible to capture elements of our earlier two example images. We liked the brightness of the cup but we also liked rich moody shadows. A little fiddling with the curves let us bottom out some of the shadows, spike the intensity of the highlights, and enjoy the best of both.
Have a tip or trick to make convert photos to black and white and make them pop? Join in the conversation below.
I don’t expect that you’ll use these techniques on every image, but I hope they’ll improve some of your pictures and that you’ll enjoy experimenting using curves in Photoshop. This type of mathematical editing gives you a good understanding of histograms and the meaning of RGB values.
Curves are possibly the most underused tool in the Photoshop arsenal, and they’re the heart of our tutorial today. Many people are put off of using them because they are not particularly intuitive and there are so many other tools available which are a bit easier to grasp out of the gate.
The formal name for the mathematical symbol for infinity, which looks like a sideways figure eight, ∞, is “lemniscate”.
Unlike Levels, where the adjustments you make are applied uniformly across the image, the Curves are applied more granularly, which makes it much easier for you, the editor, to make very subtle changes to the image. If you want deeper shadows, brighter whites, or to isolate a particular shade of blue (now gray) in the sky framed in your photo, for example, you can do so with the Curves tool.
From here you can manipulate the curve and apply presets just like you did in the previous two steps of the tutorial.
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When applying a Curves adjustment, use the black and white sliders to quickly set the black and white points (pure black and pure white values) in the image.
In the Properties panel, choose Curves Display Options from the panel menu.
The content of a photo will dictate how you edit it, so you shouldn’t obsess over correcting color in every photo. Many times, you’ll want to do little or nothing to the color. An appreciation of the curves tool and the numbers around it will help you decide what each photo needs.
Click the Curves icon in the Adjustments panel. Choose Layer > New Adjustment Layer > Curves. Click OK in the New Layer dialog box.
Add more points directly to the curve to adjust different tonal areas. Click the On-image adjustment tool in other areas of the image, and drag up or down. Move the Set Black and White Point sliders or use the Eyedropper tools to specify the darkest and lightest values in the image.
Click a point on the curve, and enter values in the Input and Output text boxes. Select the pencil icon and draw a new curve over the existing one. When you have finished, click the Smooth the Curve Values icon or to smooth the curve you drew.
Clicking more than once continues to smooth the curve further.
Now, let’s look at that little black dot on that curve. Follow it with your eyes to the left gradient bar, and then follow it with your eyes down to the bottom gradient bar. That dot represents the slightly gray, almost white, value of the cup in the photo.
To select multiple points, Shift-click points on the curve. Selected points are filled with black.
Do the same thing with any black, shadow areas with values of about 10-30. After that, you’ll have created three sample points. Since color casts in shadows are inherently harder to see, this third sample point can often be skipped without ill effect.
Increasing the slope in the middle of the curve increases contrast in the midtones.
A. On-image adjustment tool B. Sample in image to set black point. C. Sample in image to set gray point. D. Sample in image to set white point. E. Edit points to modify the curve. F. Draw to modify the curve.
G. Curves presets menu H. Set black point. I. Set gray point. J. Set white point. K. Show clipping.
Tip: Since moving the endpoints of the curve line affects all highlights and shadows, you should edit conservatively. In particular, avoid choosing the highest of the three RGB values as the target when matching red, green and blue highlight channels. Otherwise, you may find that you blow out wanted detail in the brightest part of the image. Flaws in the shadows are generally less noticeable, but you still risk blocking detail if you adjust all the shadow RGB points to the lowest of the three values. In general, turn the numbers away from their extremes.
Moving a point in the top portion of the curve adjusts the highlights. Moving a point in the center of the curve adjusts the midtones, and moving a point in the bottom section of the curve adjusts the shadows. To darken highlights, move a point near the top of the curve downward. Moving a point either down or to the right maps the Input value to a lower Output value, and the image darkens. To lighten the shadows, move a point near the bottom of the curve upward. Moving a point either up or to the left maps a lower Input value to a higher Output value, and the image lightens.
Please don’t hesitate to fire questions my way if anything is unclear.
What if we went the opposite route, though? What if we dropped the value way down instead of spiking it way up?
Starting with highlights (your #1 sample), open the individual red, green and blue curves channels one at a time and move the top right point either left or down along the outer edge of the graph so that, eventually, the three values match. As you move each point on the graph, the info palette gives you the updated output value.
How to Enhance Your Black and White Photos with Adjustment Curves
Last week we showed you how to convert your color photos to black and white photos. While the tips and tricks we shared with you yield awesome results, we’re back this week to highlight some powerful techniques to take your image to the next level.
Because the curve is unadjusted, the input (the lower gradient bar) matches the output (the left-hand gradient bar). If we were to grab that little marker on the curve and pull it down it would darken the value, and if were to raise it then it would lighten the value. Let’s take a look at what happens when we do that in the next section of the tutorial.
To select the next higher point on the curve, press the plus key; to select the next lowest, press the minus key.
Looking at the three RGB samples you’ve created, you should get an idea of any color casts that are present. You’ll typically see the same problem across all tones from highlights to shadows, though not always. Remember that a low RGB value in any of the three channels indicates an opposite color cast. Thus, a low red value indicates a cyan cast, low green is magenta, and low blue is yellow. This only applies in areas that should be neutral in color (i.e. white, gray, black).
If the image uses the full tonal range, but needs midtone contrast, Click the Curves icon in the Adjustments panel. Drag the curve into an S shape.
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Here are the steps you might take to correct color using curves, the info panel, and histograms:
By following along with the battery of more advanced tips we have rounded up for this tutorial, however, you will be able to take your black and white photos to the next level. You may not edit every photo you take to this degree, but for the ones you really want to massage, manipulate, and otherwise enhance before hanging on your wall, the techniques can add just the right amount of pop to an image.
Points on the curve remain anchored until you move them. You can make an adjustment in one tonal area without affecting other areas.
Although many people are put off by the complexity of the Curves tool, we hope after a little tinkering you have seen how the extra effort is worth the time and yields really fantastic images.
Auto applies an automatic color correction using the current default setting. To change the default setting, choose Auto Options from the Properties panel menu and set the options in the Auto Color Correction Options dialog box. You can apply an Auto Color, Auto Contrast, or Auto Tone correction to an image. For more information on these options, see Set Auto adjustment options.
With your image open, select the eyedropper tool from the Photoshop tools palette.
Be sure that the “Layers” and “Info” windows are open. Select a “3 by 3 Average” or “5 by 5 Average” sample size for the eyedropper tool. Easy one-click color correction using mid-tones
Now that we’ve looked at manual curve adjustments, let’s look at the Curve presets.