Publishers of technology books, eBooks, and videos for creative people

Home > Articles > Adobe Photoshop > Technique

This chapter is from the book

Global Color Correction

As you know by now, Photoshop often gives you three or more ways of reaching the same end result. Some people don't like this and believe that their way is the only way. Puh-leeze! Color correction is an art form that relies on your perception, experience, and interpretation of the image. With the following exercises, we'll use Levels and Curves to rescue some pretty sad photos from color cast fates worse than death.

Using Auto Color Correction

New in Photoshop 7 is a much-improved Auto Color Correction function—one that you can control to achieve some remarkable results. I am usually the first one to shy away from anything with the word "auto" or "magic" in its name. The new Auto Color Correction offers a number of controls with which you can get into the color balance ballpark quickly and easily—especially when working with digital camera files. Once you understand how Auto Color Correction works, it can save you a lot of time. Note that I am not referring to the Auto Levels, Auto Contrast, or Auto Color menu commands in the Image > Adjustments menu. I don't recommend those commands at all because you have no control over the values Photoshop uses to calculate the changes, and worst of all—you are not working with an Image Adjustment layer.

Both the Levels and Curves dialog boxes have an Auto button. Clicking Auto will perform the default corrections, regardless of where you access it. Because the interface is smaller with Levels, I use this one because I can see more of the image and get identical results. Clicking Options brings up the Auto Color Correction Options interface (see figure 4.17). It is here that you can cycle through the types of corrections or influence which values Auto Color references.

Figure 4.17Figure 4.17 The Auto Color Correction options can be set from either the Levels or the Curves dialog box.

The Auto Color Correction Options Interface has six settings that enable you to control how the color is affected:

  • Enhance Monochromatic Contrast: Photoshop clips all color channels at once, using identical values for each, making shadows darker and light areas brighter. This is the same as Image > Adjustments > Auto Contrast, or moving the shadow and highlight slider in Levels to where image information begins on the RGB or CYMK composite histogram.

  • Enhance Per Channel Contrast: Photoshop will adjust each channel separately. This is identical to moving the shadow and highlight sliders of the individual image channels to where the image information starts. This is how Image > Adjustments > Auto Levels works.

  • Find Dark & Light Colors: Photoshop uses the lightest and darkest pixels in an image for the Shadow and Highlight values. This is the same as Image > Adjustments > Auto Color and may or may not introduce unwanted color casts.

  • Snap Neutral Midtones: With this selected, Photoshop looks for a nearly neutral color in your image and then forces it to gray. Image > Adjustments > Auto Color uses this option.

  • Target Colors Clipping: Enter values here to tell Photoshop the percentage of tones to ignore. For example, entering 0.02% for both Shadows and Highlights will skip the brightest and darkest 0.02% before starting calculations. The default 0.5% value is too high. If you want calculations to be based on non-neutral colors, clicking a color swatch will open the Color Picker, where you can choose any color as the Shadow, Midtone, or Highlight target.

  • Save as Defaults: Clicking this tells Photoshop that these are the settings you want to use anytime you click the Auto button in Levels or Curves. Note: If you select this option, the Clipping value you enter will also be the new defaults for the Auto Levels, Auto Contrast, and Auto Color menu commands.

The Beauty Is in the Auto Details

Now that Adobe has added the ability to control the Auto Color Correction, I find myself adding a Levels or Curves Adjustment Layer and clicking through the options to see what is going to happen. Many times the results are very good—if I pay attention to the details.

To get the best results from Auto Color, start by checking Find Dark and Light Colors and Snap Neutral Midtones and making sure that Save as Defaults is checked. Don't worry if this ruins your image for now. By setting these as defaults, you're ensuring that Photoshop is starting with Auto Color when you click Auto in either Levels or Curves. Click OK. If making this change ruined your image, just choose Edit > Undo and the change to the image will be reversed, but the settings will be remembered.

To continue controlling how Auto Color works, reopen the interface to adjust the Target Colors Clipping values, which are both too high at .50% and will result in blocked up shadows and blown out highlights. Start by reducing the shadow value to 0 and using the up arrow on your keyboard to go up .01% at a time. Keep an eye on the image shadow and highlights; values lower than the default will create pleasant, open shadows with information and printable highlights that aren't pure paper white.

The midtone default of a perfectly neutral gray may or may not be the best choice for your images. In fact, the perfect neutral may be visually too cold. You can adjust the midtone, and best of all, as with the previous changed settings, the change is interactive.

In the image in figure 4.18, the model car is a bit flat and due to the tungsten light, the overall image is yellow. Adjusting the midtone solves the problem.

Figure 4.18Figure 4.18 The neutral gray midtone default may not be the best choice.

ch4_bluecar.jpg

  1. Add a Levels Adjustment Layer and click Options, which in this case brings up the default settings described previously.

  2. To reduce the yellow cast, I clicked the midtone color swatch in the RGB values, left the red and green alone at 128, and raised the blue values by 20 points (see figure 4.19).

  3. Figure 4.19Figure 4.19 Adjusting the midtone by raising the blue value.

  4. You can achieve the same result by simply dragging the color picker circle within the color picker. Keep an eye on the image to see the effect. In this case, the yellow was minimized and as a bonus, the blue car became even bluer.

Crop Before Clicking Auto

Consider cropping your image before using Auto Color Correction. David Bryant sent me the example in figure 4.20, where he tried Auto Color Correction but was not happy with any of the results. It wasn't until he noticed and cropped out the narrow white border on the bottom and right edge of the print that the Auto Color Correction worked, as in figure 4.21.

Figure 4.20Figure 4.20 Before

Figure 4.21Figure 4.21 After

The portrait in figure 4.22 shows an unattractive color shift that is only too typical of color prints from the 1970s and 80s. Using our knowledge of Auto Color Correction, we can fix many of the overall color problems, as shown in figure 4.23.

Figure 4.22Figure 4.22 Before

Figure 4.23Figure 4.23 After

ch4_teenager.jpg

  1. Crop the image to remove the white border. As figure 4.24 shows, you can rotate the Crop tool to straighten out the image while cropping. To rotate your crop, move the mouse about a quarter-inch to the outside of the corner handle. The mouse will change into a curved arrow that you can use to rotate the crop bounding box.

  2. Figure 4.24Figure 4.24 Cropping and rotating the image before using Auto Color Correction.

  3. Add a Levels or Curves Adjustment Layer. In this example, I used Levels, because the dialog box is smaller and lets me see more of the image. Click Options to access the Auto Color Correction settings. You should see a change in your image as soon as Auto Color Correction Options pops up, and it's not a good change, as figure 4.25 sadly illustrates. The image is now much too contrasty and coldly blue.

  4. Click through the three options. With this image, Enhance Channel Contrast with Snap Neutral Midtones is the most effective. Because the default Clipping values are too high, I changed them to 0.20%, which reduced the highlights on his lapel and maintained image detail (see figure 4.26).

  5. Figure 4.25Figure 4.25 Add a Levels Adjustment Layer and Click Options.

    Figure 4.26Figure 4.26 Changing the Option settings from the defaults can make a big difference.

  6. Click OK to accept the Options settings and click OK on the Levels dialog box to commit the changes. Compare the image before and after Auto Color Correction by turning the Adjustment Layer visibility off and on.

All in all, explaining how to use Auto Color takes longer than actually making the changes to achieve good and quick results.

Color Correction with Levels Eyedroppers

Working with the Levels or Curves eyedroppers to define the one, two, or three neutral areas of white, gray, or black will often remove a bothersome color cast. Figure 4.27 shows a scene photographed with a Nikon D100 digital camera in the late afternoon in Helsinki, Finland. You'd never know it from the photograph, but the building exterior is actually snow white. With a few clicks in Levels, you can restore the gleaming white facade, as seen in figure 4.28. Please note: The color cast in this example is not typical of the Nikon cameras, rather it was my fault for taking the picture with the wrong camera settings while rushing around before sunset.

Figure 4.27Figure 4.27 Before

Figure 4.28Figure 4.28 After

ch4_finland.jpg

NOTE

Before using the Levels or Curves eyedroppers, define the white and black target colors as described in Chapter 2 "Improving Tone and Contrast." For printing to an inkjet printer, use the HSB scale and set the white target color to 96% brightness, or RGB 245, 245, 245, and click OK. Double-click the black eyedropper and set the shadow target color to 5% on the HSB scale, or RGB 12, 12, 12.

  1. The first step is to identify the color cast. If you're working with a well-calibrated monitor and have a good sense for color, you'll see that the building is too yellow. If you're not sure about color or your monitor, use the Info palette. Set your Eyedropper to Sample 3 by 3 Average on the options bar, and look for something you know should or could be neutral. This image has large expanses of white, but every image will be different. When you position the Eyedropper over a neutral color, the Info palette will reveal the color cast (see figure 4.29). In this case, the very low blue value of 83 signifies that the image is very weak in blue, which translates to strong in yellow, so the image has a yellow color cast.

  2. Figure 4.29Figure 4.29 The values in the Info palette help you identify the color cast.

  3. I added a Levels Adjustment Layer and selected the white eyedropper. I clicked the lightest part of the building to define a new white point. Clicking with the eyedropper not only redefines the pixels clicked to white; it also neutralizes them. In the Info palette, I noted that the values of red, green, and blue are equal, proving that I removed the color cast, as shown in figure 4.30. You should experiment to find the best neutral points. Try as many areas as you like. Each click of the eyedropper will re-examine and adjust the image all over again.

  4. Figure 4.30Figure 4.30 Using the Levels white eyedropper to define a new white point improves overall color and contrast.

    TIP

    (Option + drag) [Alt + drag] the Highlight slider to the left, as you see in figure 4.31. Photoshop will reveal where the true highlight is. In this image, I ignored the lightest areas in the specular highlights of the golden crosses and concentrated on the building as circled. This technique works for the shadow point as well.

    Figure 4.31Figure 4.31 Finding the highlight point of an image.

  5. Next select the midtone eyedropper and click the shady side of the building, as shown in figure 4.32. If you think about it, a white building in the shade should be gray, so this is a good way to find a neutral midpoint.

  6. Figure 4.32Figure 4.32 Using the Levels gray eyedropper to define a neutral midpoint removes even more of the color cast.

  7. On many images, correcting for the white point and midtone may be enough. However, on this image, I also selected the black eyedropper and used the darkest of the little windows to set the new black point (see figure 4.33).

  8. After defining the white and black points, take a second look at the image. If the image looks too dark or too light, use the midtone slider to lighten (by moving the midtone slider to the left) or darken (by moving the slider to the right).

  9. Figure 4.33Figure 4.33 Using the black eyedropper on a black point improves image density. Notice that it makes the sky come to life!

Multiple Color Corrections with Levels

Often, pictures taken at the same time will share the same problems. Whether it was bad lighting, bad processing, bad storage, or simply bad luck, you can save time and effort by fixing one, then applying that same adjustment to the rest.

The images in figure 4.34 were all taken at the same event, and all suffer from the same unfortunate lighting. By using a Levels adjustment layer on one, then sharing that same adjustment layer with the others, I was able to fix all four, as seen in figure 4.35, without four times the work.

Figure 4.34Figure 4.34 Before

Figure 4.35Figure 4.35 After

ch04_costumeparty.jpg

  1. First we need to adjust one of the images using the Auto Color Correction technique addressed previously. Add a Levels Adjustment Layer and click Auto. As figure 4.36 shows, the initial Auto Color setting is rather good, but we can still improve the image with one more click.

  2. We have an ideal neutral reference source to work with—the white wall in the background. Notice how the right side is still slightly green? By clicking the wall with the gray Levels eyedropper, the last hint of the colorcast is removed as seen in figure 4.37.

  3. Figure 4.36Figure 4.36 Using only Auto Color.

    Figure 4.37Figure 4.37 Correcting the color by clicking on the white wall with the midtone eyedropper.

  4. Click OK to accept the image correction.

  5. Without closing your corrected image, open another of the problem images and drag the adjustment layer from the corrected image onto the second image, as in figure 4.38. This applies the same correction to the new image.

  6. Figure 4.38Figure 4.38 Dragging the adjustment layer to a new image.

Subtle Color and Exposure Improvement with Curves

Not all images have overwhelming or obvious color casts. In fact, some images require a delicate touch to remove the color cast and adjust exposure. In this example, the photograph is off just a bit—meaning that it is only slightly too dark and red (see figure 4.39) In this example, I set new black, white, and gray points and improved the exposure with a Curves Adjustment Layer, and then fine-tuned the overall saturation with a Hue/Saturation Adjustment Layer. These changes, shown in figure 4.40, enable you to appreciate the beauty of the young woman.

Figure 4.39Figure 4.39 Before

Figure 4.40Figure 4.40 After

ch4_flowergirl.jpg

  1. Add a Curves Adjustment Layer. Use the white eyedropper to set the wall just above her flower to white, the black eyedropper to set the shadow beneath her chin to black, and the gray eyedropper to set the wall in the upper left as neutral gray (see figure 4.41).

  2. Figure 4.41Figure 4.41 Setting new white, black, and gray points using the Curves eyedropper.

  3. Boost the shadows and midtones by dragging the center of the curve upward to lighten the image and add the sparkle of a well-exposed photograph (see figure 4.42). Be careful to monitor the highlights on the girl's skin and flower in the Info palette so they are not forced to pure white.

  4. Figure 4.42Figure 4.42 Lighten the image with Curves.

  5. Not all portraits require the following step, but in this instance the teenager's tanned arms are over saturated and visually distracting. To reduce the saturation, I added a Hue/ Saturation Adjustment Layer and decreased the overall saturation by –25, as seen in figure 4.43.

  6. Using the gradient tool set to default black and white, I drew a gradient on the Hue/Saturation layer mask to shield the face from the desaturation, as shown in figure 4.44.

    Figure 4.43Figure 4.43 Decreasing the saturation reduces the heavy orange cast.

    Figure 4.44Figure 4.44 Taking advantage of the layer mask to control where the change takes place.

Using Curves with Luminosity

In most cases, using the target eyedroppers in Levels or Curves is an excellent method for removing color casts and adjust image contrast. But as with all good things, sometimes they do add unwanted density or saturation. To avoid the unwanted punch, combine the power of a Levels or Curves Adjustment Layer with the Luminosity Blending Mode, as shown in figures 4.45 and 4.46.

Figure 4.45Figure 4.45 Before

Figure 4.46Figure 4.46 After

ch4_flowerpot.jpg

  1. I used the Curves black, gray, and white eyedroppers on the areas indicated in figure 4.47 and opened up the exposure with one Curves adjustment. This added too much false saturation to the clay pot.

  2. Figure 4.47Figure 4.47 Using eyedroppers and a Curves adjustment makes the image too saturated.

  3. Changing the Blending Mode of the Curves Adjustment Layer to Luminosity as seen in figure 4.48 offsets the unwanted saturation while maintaining the neutral tonal values. Toggle the Blending Mode from Luminosity to Normal to appreciate the difference.

  4. Figure 4.48Figure 4.48 Changing the Adjustment Layer Blending Mode to Luminosity lessens the false saturation.

Peachpit Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from Peachpit and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about Peachpit products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites; develop new products and services; conduct educational research; and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email ask@peachpit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by Adobe Press. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.peachpit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020