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Monday, January 7, 2008

Unlimited Sharpness With Helicon Focus

Helicon Focus gives you the ability to cheat depth-of-field limitations

This Article Features Photo Zoom

ABOVE: The pro version of Helicon Focus offers a Retouch feature, where the user can copy elements from a source image back onto the final composite. 1) The Retouching tab brings up this screen. 2) The list of images from which to choose for the sharp area to be cloned. 3) The properties of the Cloning Brush. 4) The source area being cloned (left) and the matching area that will receive the cloned information (right).

Since you're reading this magazine, you already know that photography in the digital age is breaking all the old rules and pushing the limits of film. Across these pages, digital capture, versatile software and artistry combine to fulfill creative vision that might have been imaginable 10 years ago, but not achievable. Now another barrier—the physical limits of depth of field—is overcome by software called Helicon Focus.

The In-Depth Challenge
Depth of field, or the range of focus, is a problem in many photographic applications. It's most troublesome in micro/macro photography and in long-lens photography, where the area of focus is minimal in proportion to the range of view. But depth of field is also a challenge in landscape, architectural and product photography, where the foreground and the background require equally sharp focus.

High-magnification microscopic lenses must be used at their widest numerical aperture to render fine detail, and this translates to a small range of sharpness—easily less than 1mm, depending on the amount of magnification. In macro photography, working at lower magnifications, the lens may be stopped down to ƒ/11 or ƒ/16, but these settings still offer limited depth of field. Traditionally, we've been forced to choose which part of the subject will have the greatest detail, such as the eye of an insect or one stone in a piece of jewelry. In the past, these limitations have been accepted by photographers who have met the challenge with creative positioning of the focused area in the frame.

Everything from details just inches from the lens to trees in the background is in focus with the use of four images and Helicon Focus. A Canon EOS 5D with an EF 17-40mm lens set to 17mm at 1⁄250 sec. and ƒ/11 was used for capture.

In general photography, there's often both a foreground subject and other secondary subjects that all require sharp rendering. To accomplish this, the photographer might choose a wide-angle lens to achieve the needed depth of field. But this solution gives a forced perspective, distorting the foreground and making the background seem unnaturally distant. A telephoto lens will give a more desirable compressed perspective, but because of the focal length's inability to offer enough depth of field, both the foreground and background can't be rendered sharp.

The issue of range of focus has been a limitation of photographic capture since the first use of silver halide. The solution has come from a surprising source, a professor of economics in the Ukraine. Danylo Kozub, whose hobbies are digital photography and computer programming, first approached the problem as a favor to his brother, a chemist trying to photograph crystals with an optical microscope. Within a few days, Kozub, whose Ph.D. in macroeconomics was closely connected with mathematics and computer simulation, determined a way to combine multiple images into one perfectly focused result. The commercial product based on the same algorithm was released in 2003 through a small software company, Helicon Soft Ltd., but it didn't become known to many photographers until 2005.