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

Home > Articles > Adobe Photoshop > Technique

This chapter is from the book

Reducing Digital Camera Noise and Moiré

Digital cameras are based on a variety of technologies, including scanning, peizo, three-shot, and the one-shot cameras. Every digital camera technology has its pros and cons, which have been addressed in Real World Digital Photography, which I coauthored with Deke McClelland.

The one-shot cameras work just like your film camera, except that a CCD (Charged Coupled Device) with a color mosaic filter replaces the film. The CCD structure, in combination with the filter, can cause color artifacts that look like little twinkles of colored lights or rainbow-like moiré patterns might be visible in areas of high-frequency, fine-detail information, such as eyelashes, flyaway hair strands, specular highlights, small branches of trees, or woven fabrics, as seen in Figure 5.34.

Even if you don't use a digital camera, you might pick up moiré patterns when scanning images with fine fabrics, and you can use the following techniques to take care of those problems.

Blurring and Sharpening in Lab Color Mode

Moiré and color artifacts like those in Figure 5.35 show up as problems in the color channels. By separating the color information from the black-and-white image information, you can fix what's broken—the color artifacts—without affecting what's not—the tonal information, as seen in Figure 5.36.

TIP

When using any of these techniques to remove moiré or color artifacts, make sure you view your image at 100% monitor view to accurately see what is occurring.

Figure 5.34Figure 5.34 Extreme rainbow moiré problems might be impossible to eradicate completely.


 

Figure 5.35Figure 5.35 Before


 

Figure 5.36Figure 5.36 After


ch5_moire_crop.jpg

  1. Choose Image > Mode > Lab Color to convert the RGB file to Lab.

  2. Make the "a" channel active and then press ~ to see the full-color image. Run the Gaussian Blur filter with a high-enough radius to soften the artifacts. Don't try to eradicate all artifacts at once because you will be repeating the Gaussian Blur filter on the "b" channel in the following step (see Figure 5.37).

  3. Figure 5.37Figure 5.37 Blurring the a channel to lessen the color artifacts.


  4. Select the "b" channel and run the Gaussian Blur filter on the "b" channel. Use a higher radius than you used on the "a" channel as the "b" channel usually has more color artifact problems.

  5. Select the Lightness channel and choose Filter > Sharpen > Unsharp Mask to sharpen up the black-and-white information, as seen in Figure 5.38.

  6. Figure 5.38Figure 5.38 Sharpening the Lightness channel to sharpen the black-and-white image information.


    NOTE

    It would be unwise to use my values as the right values for all image problems. The Gaussian Blur and Unsharp Mask settings shown here offer good starting points. You might need to increase or reduce values to fine-tune the artifact removal in your images.

  7. Make the composite channel active and inspect the image for any stray color artifacts. Use the Sponge tool set to Desaturate to brush away any artifacts that the global approach might have missed.

  8. Using this Lab blur and sharpen technique can sometimes desaturate the entire image, making it look flat and faded. To offset this undesired side effect, use a Hue/Saturation Adjustment Layer to boost the saturation, as seen in Figure 5.39.

  9. Figure 5.39Figure 5.39 Boosting overall saturation.


This technique might sound like a lot of steps but, thankfully, the entire procedure and settings are actionable. By making a Photoshop Action, you can batch process an entire folder of digital camera images in a fraction of the time it would take to do this step-by-step. Go to http://www.digitalretouch.org/ch5 and download the Action moiré_removal.atn. Another practice file, ch5_costume.jpg, is also on the site.

Using Quantum Mechanics Software

If you work with a lot of digital camera files, making a modest investment in Quantum Mechanic Lite or Pro (http://www.camerabits.com) to do all the previously described work for you and do it better makes a lot of sense. Both Quantum Mechanic Lite and Quantum Mechanic Pro are designed to remove color noise and artifacts. They work very well with Kodak's cameras and high-end cameras that don't do any similar kind of filtering in their host software.

Quantum Mechanic Lite (see Figure 5.40) uses a quick filtering mode with simple controls for busy workflows, such as newspapers. QM Pro (see Figure 5.41) has complete control over all the parameters of color filtering, and includes a more advanced filtering mode to retain color detail. Best of all, both flavors of the plug-in work in 48-bit mode and the sharpening is much more effective in 48-bit mode, producing less artifacting with smoother results and better shadow noise reduction. After selecting specific areas, use the Quantum Mechanic Moiré Eraser to take care of any stray color artifacts and color moiré, as seen in Figure 5.42. The Moiré Eraser is a heavy-duty filter and must be used with care.

Both Quantum Mechanic Lite and Quantum Mechanic Pro will remove some color moiré, but only if the moiré pattern waves are close together. As the waves get farther apart, the radii values need to be increased, and you can run the risk of desaturating other color detail in the image. Figure 5.43 shows an extremely bad example of wide-band moiré. As Figure 5.44 reveals, the moiré problem has contaminated all three color channels, making this a tough, tough job to fix. After separating the red sweater onto its own layer, I was able to minimize the color artifacting of the moiré with repeated use of Quantum Mechanic Pro and selective use of the Quantum Mechanic Moiré Eraser. The results in Figure 5.45 are certainly better.

Figure 5.40Figure 5.40 Quantum Mechanic Lite simplifies the moiré reduction process.


 

Figure 5.41Figure 5.41 Quantum Mechanic Pro offers additional controls to reduce moiré.


 

Figure 5.42Figure 5.42 Quantum Mechanic Moiré Eraser is used to clean up stray color moiré problems.


 

Figure 5.43Figure 5.43 An extreme case of color moiré with very wide bands.


 

Figure 5.44Figure 5.44 By inspecting the three color channels you can see that the moiré problem is throughout the entire file. This will make it especially tough to retouch.


 

Figure 5.45Figure 5.45 After using Quantum Mechanic Pro and Quantum Mechanic Moiré Eraser, the color moiré has been reduced.


Avoiding Moiré Patterns When Shooting Digital Pictures

If you notice moiré problems while you're taking pictures with digital cameras, you can lessen them with the following tips:

  • Move the camera closer or farther away from the subject by just a few inches to change the relationship between the grid of the CCD color filter and the high-frequency information that is causing the problem.

  • Open the aperture to use a larger ƒ-stop. This decreases the depth of field, which means that less of the subject matter is in focus. The out-of-focus parts have lower spatial frequency content and hence fewer aliasing artifacts. The in-focus areas might still reveal some artifacting.

  • Some people recommend defocusing the camera a smidgen and then over-sharpening the file in Photoshop. I'm not a huge fan of that approach, but offer it as a technique you can experiment with.

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