Tuesday, June 24, 2008
XDR, Part III
Double exposure gives you two times the image information to use in a final image
If posterization occurs, you can more precisely blend a specific range of the tonal scale by adding a luminance or contrast mask. Go to the Channels palette and Command/Control click on the RGB channel. This loads a selection of the highlights. If you want to create a selection of the shadows, go to the Select menu and choose Inverse. Add a layer mask by clicking on the mask icon at the bottom of the Layers palette. The selection automatically becomes a mask, restricting the adjustment to the specified areas.
To refine transitions, you can modify the brightness and contrast of the mask by applying Curves to it (Image > Adjust > Curves). You can further refine these masks by locally adjusting or painting on them. (See Resources under “R/Evolution” at www.digitalphotopro.com for more on this.)
If posterization still persists, you may need to incorporate an additional intermediary exposure. While blending the two images, apply the same principles and be mindful of the same concerns during acquisition. Avoid posterization and dramatically reduced midtone contrast. Aim for full detail with slightly low contrast, but good midtone separation and naturalistic blends between the two versions. This provides an optimum base image that you can enhance further without encountering undesirable artifacts.
1) The Layer Style palette with sliders set to constrain adjustment to shadows
2) The Layer Style palette with sliders set to constrain adjustment to highlights
3) Shadow mask
4) Highlight mask
5) Simple radial gradient mask
The initial blended image is only a starting point. Once the best blend is achieved, further enhance the blended image with adjustment layers that adjust both image layers simultaneously and/or independently.
When working on image files, use a flexible workflow. Use layers and adjustment layers. Don't flatten. Keep your layer stack intact to preserve your ability to make future improvements.
But Wait, There's Still More...
The results can be dramatic. When using these techniques, you'll be challenged to see in new ways. Difficult shooting conditions will become easier for you. Many more image-making opportunities will become available to you. It's well worth investing the time to master these techniques as the versatility they will afford you will be both rewarding and profitable.
When you want to exceed even these new boundaries, consider HDR merges to fully advance into a kind of photographic image-making that can exceed the range of brightness that the human eye can't accommodate at one moment in time. Your images will provide you and your viewers with a new window on the world.
John Paul Caponigro is an internationally respected fine artist, a member of the Photoshop Hall of Fame and the author of Adobe Photoshop Master Class and the DVD series R/Evolution. Get more than 100 free downloads and a free subscription to Insights at www.johnpaulcaponigro.com.