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Tuesday, February 2, 2010

Go Ultra Wide!

By William Sawalich Published in Shooting
Go Ultra Wide!

What happens when you have to tilt up just a little bit to get the top of a crucial element in the frame? The lines begin to point outward at the upper corners of the scene. Sometimes this effect is a desirable one. But when the distortion isn’t an intention but a consequence of the composition, the only way to fix it (short of recomposing) is to turn to the computer. Thankfully, this is a fairly straightforward and often effective solution.

CORRECTING DISTORTION

For small distortions, the Lens Correction filter in Photoshop makes perspective changes quick and easy. (It’s also effective for repairing barrel distortions.) Simply adjust the Vertical Perspective slider to the left to repair distortions caused by tilting an ultrawide up, known as “keystoning,” or slide to the right to repair distortions caused by looking down.

If you find this repair isn’t quite enough, a little more powerful control comes from the Transform > Perspective tool. If the camera’s tilt isn’t directly vertical, but rather canted to the side as well, the Distort, Skew and Perspective adjustments in the Transform tool allow you to control lines at the edges of the frame independently. These corrections require working in layers, and ultimately cropping out the now missing corners of the new composition, but with enough room in the original framing that it’s a solid fix for most ultrawide distortions.

Most editing programs contain some sort of distortion correction. Photoshop Elements, for example, has the Correct Camera Distortion filter for fixing keystoning and parallax from ultrawides, or you can use plug-ins and stand-alone software like PTLens and DxO Optics Pro that are designed for exactly these repairs.

Computers also come in handy for another ultrawide fix: filtering. Because many ultrawide lenses have a convex front element that can’t accept optical filters, or their view is so wide that filters cause significant vignetting, many photographers find that filtration with ultrawides can be achieved more easily in the computer. Some ultrawides do accept internal filters at the rear of the lens, but even these can be problematic. When working with a polarizer on an ultrawide landscape, for instance, the angle of view is so wide that the polarization isn’t consistent across the scene—making for a photograph with uneven, inconsistent blue skies.

Canon EF 14mm ƒ/2.8L II USM

ULTRAWIDE LENSES TO CONSIDER

Canon’s EF-S 10-22mm ƒ/3.5-4.5 USM zoom lens provides ultrawide coverage for sub-full-frame cameras like those in the Digital Rebel lineup. In 35mm-equivalent terms, this ultrawide lens actually zooms to a moderate wide angle covering a 16-35mm range. The fast and silent ring-type ultrasonic motor complements full-time manual focus—which can focus on subjects as close as 9.5 inches. Three aspherical elements and a Super-UD element keep image quality high across the zoom range. The lens accepts 77mm front-element filters. Estimated Street Price: $750.

For full-frame, prime-lens shooters, Canon’s updated EF 14mm ƒ/2.8L II USM is a fast lens with redesigned optics that include two aspherical elements and two UD elements. Such high-tech optical innovations are designed to minimize aberrations that hinder contrast and sharpness—particularly at the edges of the frame. The 114-degree angle of view stops just short of a fisheye, making the image quality that much more impressive. This quality, unfortunately, doesn’t come cheap. It accepts gel filters internally. Estimated Street Price: $2,200.
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