Saturday, September 1, 2007
Focusing On Focal Lengths • Cave Photography • What You Should Bring • Tilt/Shift Lenses For Landscapes
What You Should Bring
Via the Internet
The advantage of a tilt/shift lens is that the front elements can be tilted to modify the plane of focus from the normal angle, which is perpendicular to the lens, to an angle that’s more or less than 90 degrees to the lens. Imagine two parallel planes, one perpendicular to the end of the lens and one at the front edge of the area of sharpness. When the plane at the end of the lens is tilted, the plane of sharpness tilts also, extending the range of the sharpness along the angled plane. Maximum depth of field is achieved when the top of the lens is tilted away from the photographer and a small lens aperture is used.
There are three basic focal lengths available. Canon offers 24mm, 45mm and 90mm tilt/shift lenses, and Nikon offers the 85mm PC Micro Nikkor. The two I’ve used the most for landscapes are the 24mm and 90mm. Each has a different purpose. The 24mm is especially useful when a moderately wide angle is needed, when the foreground is quite important and needs to be kept in focus along with more distant elements within the composition. It’s possible to have a foreground detail within inches of the lens sharply rendered, while also getting a sharp capture of the mountains in the background far away.
The 90mm lens is a moderate telephoto and is best for some depth compression in a composition, yet everything within the view needs to be sharp. This is often difficult with telephoto lenses because they typically offer minimal depth of field. The compression can be emphasized by adding either a 1.4x or 2x tele-extender to the 90mm tilt/shift lens.
Considering the 1.5x or 1.6x magnification of a smaller-sensor D-SLR, the compression is emphasized even more when using the longer focal-length lens. A perfect example for use of an 85mm or 90mm tilt/shift lens is a carpet of flowers photographed from a low angle, with all of the flowers tightly compressed and, due to the tilt, all of them in focus across their tops. This particular perspective is impossible to achieve with any other type of telephoto lens.
If I could have only one, I’d choose the 90mm, mainly because it can capture images that no other optic can. But if most of your landscapes are wide-angle, you might opt for the 24mm.
If your subject isn’t moving and you’re shooting with a tripod, you can have unlimited depth of field with new software called Helicon Focus (www.heliconfocus.com). Without reframing, adjust your focus through consecutive shots to cover the entire image. The software combines the images by keeping all sharp areas and masking the unsharp, and the result is complete depth of field, with objects both near and far in perfect focus. This technique can be used with any focal-length lens, and it takes up no space in your camera bag.
The shift factor in the tilt/shift lens is mostly used by architectural photographers for perspective control. There’s a way to use the shift features for three-shot panoramas when using a small-sensor D-SLR, but that’s another column.
> Visit www.geolepp.com.
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