Digital Outback Photo
- Photography using Digital SLRs

 

Workflow Techniques #090

Adaptive shadow and/or highlight correction

essay by Uwe Steinmueller

 
 

The following article is a short section from our new book "The Art of Fine Art printing"

 

 

We talked a lot about shadows in the section on global tonality tuning (in the book). In fact, tools such as Levels and Curves understand shadows differently than we normally do. They consider a shadow as pixels with reduced brightness. Let’s demonstrate what we mean with this example image:


Real shadows and dark regions

This picture contains dark letters but also real shadows. From their pixel brightness, the black letters, although in the sun, may be as dark or even darker than the real shadows. Curves, as well as Levels would treat both the same way. That is not really what we intend when we plan to open up shadows a bit.

In situations like this, there exist more and more tools that work adaptively; they take into account the context in which the pixels reside and not merely a single pixel value alone. The best known tool currently is Photoshop‘s Shadow/Highlight tool. Below is a demonstration target we created (available with the book) to show the principles of how Shadow/Highlight works.


Shadow/Highlight test chart (©Uwe Steinmueller)

There are five incrementally darker dots in each column identical in both columns. It is well known that we perceive the same brightness differently, depending upon its context:

  • Bright spots look brighter in a dark context
  • Dark spots look darker in a bright context

This should illustrate that treating all pixels equally, as with Curves and Levels, is not helpful at all times. Why don’t we see more of these adaptive tools today? Because they are:

  • Computing intensive
  • May have color-shift side effects
  • Sometimes create issues at their edges (e.g. show halos – watch out for them)

Shadow recovery

This is the result when Shadow/Highlight is used to open up shadows:


Open up the shadows

This we can observe:

  • All spots in the bright area remain unchanged
  • The dark background brightens up
  • The three darker spots on the darker background changed brightness

Highlight recovery


Tone down highlights

Now, here is what we can observe:

  • All spots in the dark area remain unchanged
  • The bright background darkens
  • The four brighter spots on the brighter background change their brightness

True, you could accomplish the same thing with complex masking, but the main drawbacks would be:

  • More complicated, involving much more work
  • With real world images and fine details, masking can become more than merely a minor challenge

More and more adaptive tools in the Market

  • RSP/RSE Fill Light
  • Bibble's 4.7 uses Perfectly Clear image correction from Athentech Technologies
  • HDRSoft's Tone Mapping plugin
  • some other tools
  • many more to come

Conclusion

While Curves are the central tool for global tonality corrections new adaptive tools allow us to improve our images beyond that level.

If you find tonality hard to master then you are not alone. Tonality is one of the hardest parts to master with photographs and we learn every day. Try to improve and follow your vision. There is not a single right answer.


 

 

This is one of the many techniques we will teach during the 2006 Summit. We will also work with you 1 on 1 and help you with your own images and with how to use this technique, and many others, in your own work. Click here to read a detailed description of the 2006 Digital Fine Art Summit. Joseph Holmes will join the Summit 2006 as a guest instructor means you can ask this world class printing expert directly.

About the Fourth Annual Photography & Fine Art Printing Summit

The 4th Photography & Fine Art Printing Summit will take place November 10th to 13th, 2006, in Page, Arizona. Seats are limited. In addition to studying color management and color spaces, we will also do field photography in stunning locations such as Antelope Canyon, Lake Powell and Horseshoe Bend, as well as study Raw conversion, Photoshop processing, image optimization, printing. We will also conduct print reviews of your work created during the Summit. Find out all the details of this unique learning and photographing opportunity on the 2006 Summit page.

 

 

 
 
 
   

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