Autoblend for better depth of field | Image processing techniques
Autoblend for better depth of field | Image processing techniques | ||
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A relatively new, more sophisticated technique for increasing depth of field within an image is to take a series of images at different focus points, and stack or blend them together automatically in an image-processing program. Several specific programs are available such as Combine ZM and Helicon Focus, while the latest version of Adobe Photoshop, CS4, has an 'autoblend' facility for doing this. The basic idea is to shoot a series of images of a subject at different focus points within the subject (the precise number will depend on the size of the subject). This can be done either by moving the entire camera for each exposure, or refocusing the lens. By using a fairly wide aperture, for example f/5.6, diffraction will not be an issue, and you will be using the optimum aperture of the lens, as well as keeping the background out of focus. The images are then loaded into the software package, which then analyzes the images and selects the sharpest sections of each one and blends them together. In most cases this works remarkably well, though occasionally some retouching may be required of artifacts that have been formed during the process. Moving the camera or refocusing the lens for each image leads to some perspective distortion of the subject. If you have a focusing rail, use this to move the camera toward the subject by equal amounts, though it is not strictly necessary. | ||