Tuesday, June 26, 2007
Extending Depth Of Field
Using multiple exposures and sound camera and software technique, you can defy the laws of physics
The ability to reproduce detail is one of the essential characteristics that defines the photographic medium. While there are many similarities between the camera eye and the human eye, there are also significant differences between the two. One of the most significant differences is that the camera eye can achieve a much greater area of focus than the human eye can at one time. This has never been more true than today.
Beyond Traditional Practices
You can extend focus beyond the physical limitations of any lens/camera system with the appropriate camera practices and software—by compositing multiple exposures.
1) Bracket focus.
2) Layer separate exposures together.
3) Mask the top layer(s).
Make multiple separate exposures, each optimizing focus in different image areas.
In Adobe Photoshop, open exposures with varying points of focus. Go to the Layers palette, drag the Background Layer from one document into the window of the other, holding the Shift key before dropping the new layer down.
Hide out-of-focus information in the layer on top and reveal in-focus information in the layer below. Target the top layer. Add a layer mask (Layer > Layer Mask > Reveal All or Hide All). The type of mask used to blend exposures can be relatively simple to create; make a gradient mask using the Gradient tool; optionally, make a mask manually using a soft-edged Brush tool. You can even use the two in combination with one another. (For more on these techniques, see my column in the March/April 2006 issue of Digital Photo Pro).