Monday, March 3, 2008
Introduction To XDR
Extending the dynamic range in your images is possible with sound technique and a little software magic
|1) Layer Style sliders constraining adjustment to shadows||2) Layer Style sliders constraining adjustment to highlights|
|3) Shadow mask||4) Highlight mask|
When you need to make aggressive adjustments and find that midtone separation is adversely affected consider making selective adjustments with layer masks in Photoshop.
You can use the Blend If sliders found in the Layer Style menu to restrict an adjustment to either the shadows, midtones or highlights. Double-click on the layer to activate the Layer Style menu. Then use the sliders in This Layer to remove the effect on the background layer. For smoother transitions, feather the effect by holding the Option key and splitting the sliders apart.
To more precisely target a specific range of the tonal scale, you can quickly make precise luminance or contrast masks. 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. Make a Curves adjustment layer and create an appropriate adjustment. The selection automatically becomes a mask, restricting the adjustment to the specified areas.
To further refine transitions in the midtones, after creating the adjustment layer, you can modify the brightness and contrast of the mask by applying Curves to it: Image > Adjust > Curves. Note that you can't create an adjustment layer for an adjustment layer mask; you must apply the adjustments directly to the mask, making them permanent. (See the resources posted at www.digitalphotopro.com under Revolution for more on this.)
You can make industrial-strength adjustments to an image using the Blend modes Multiply and Screen found in the Layers palette. Multiply dramatically darkens an image; it's like registering two transparencies on a light table. Screen dramatically lightens an image; it's like registering two projected images. Blend modes can be applied with any layer. They can be combined with a Curves adjustment for even stronger effects.
Because their effects are so strong, you'll want to modify their intensity using the Opacity slider or restrict their effects using Blend If sliders or a contrast mask. These effects can be helpful in making very bright highlight and very dark shadow detail more visible.
Learn more from John Paul Caponigro using his free PDFs and test files found at www.johnpaulcaponigro.com.
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