Friday, July 20, 2007
Add extra visual excitement to your portraits, scenics and more with the extreme perspective of wide-angle lenses
Zoom lock. Some zoom lenses have a zoom lock, which locks the lens at its shortest physical length for easy transport. Lenses without this feature probably will extend to their longest physical length as you carry them, which can be annoying.
Aspherical elements. Standard spherical lens elements can't focus light rays passing through the center at the same plane as light rays passing through the edges. This is called spherical aberration, and results in a loss of image sharpness and distortions. Aspherical elements correct this, and are especially helpful in zoom lenses, which need corrections at a range of focal lengths, not just one.
Low-dispersion elements. Conventional lens elements tend to focus different wavelengths of light at different distances (blue closer to the lens, green farther behind it, red farthest behind it). They also spread colors when light rays pass through the lens at an angle. These effects are called chromatic aberrations, and extra-low dispersion elements (also called super-low-dispersion, ultra-low-dispersion and similar) reduce their effects. Such elements are especially helpful in zoom lenses because of the variance of chromatic aberrations at different focal lengths.
Internal focusing. With standard focusing systems, the lens increases in physical length as it's focused from infinity to close range, and the front element rotates during focusing. The first can throw a tripod off-balance, and the latter can cause difficulties maintaining proper orientation with polarizers and graduated filters. Internal focusing eliminates both problems, by moving smaller internal elements instead of the large front ones. Internal focusing also makes for smaller, lighter lenses. But be aware of the effects of internal focusing on maximum magnification. If you're into close-up photography, you can get a closer minimum focusing distance, but less magnification with internal focusing.
Distortion Correction Software
Lens Aid: Software can fix optical flaws in digital images
A variety of software programs effectively correct distortions, chromatic aberrations, vignetting and other defects, optimizing the performance of your lenses. For the record, lens distortion refers to the unrealistic curving that appears in images taken with traditional zoom lenses. Chromatic aberration, often referred to as color fringing, is the bending of light of various wavelengths at different angles as it passes through the glass. Vignetting can be caused by filters that are attached to a lens and block light around the outside of the filter. If your photos have dark corners, that's vignetting.
DxO Optics Pro software (www.dxo.com) fixes images by measuring how various lenses perform with different sensors. Based on those unique combinations, chromatic aberrations, distortions and vignetting are removed automatically. The DxO Optics engine uses technology that avoids increasing noise when performing these corrections. List Price: $159.
Basic lens correction tools are found in Adobe Photoshop CS3, Camera Raw and Lightroom (www.adobe.com). In Photoshop, go to Filter > Distort > Lens Correction. In Camera Raw, go to the Details tab. In Lightroom, these tools are found in the Develop Module > Lens Correction. List Price: $649 (CS3); $299 (Lightroom).
LensDoc (www.andromeda.com) is a Photoshop plug-in that fixes barreling, pincushioning and other effects sometimes caused by zoom and wide-angle lenses. The latest version features new 16-bit compatibility and can adjust an image's point of view. Use the software's lens corrections or develop your own correction curves. List Price: $119.
Digital Film Tools 55mm (www.digitalfilmtools.com) offers easy-to-use tools that quickly fix images. The software controls distortion in four ways, all using sliders: distortion (quickly bows and pinches an image); anamorphic squeeze (stretches or compresses an image); and curvature x and curvature y (controlling distortion on one axis at a time). List Price: $245.
If you like the creative curvilinear effect that a fish-eye lens applies to your images, but without the hemispheric distortion, check out the Fisheye-Hemi plug-in (www.imagetrendsinc.com). The software corrects image perspective, straightens vertical lines and restores the natural appearance of people while preserving more of the image's original resolution. List Price: $29.
Canon | (800) OK-CANON | www.usa.canon.com
Nikon | (800) NIKON-US | www.nikonusa.com
Olympus | (888) 553-4448 | www.olympusamerica.com
Pentax | (800) 877-0155 | www.pentaximaging.com
Sigma | (800) 896-6858 | www.sigma-photo.com
Sony | (877) 865-SONY | www.sonystyle.com
Tamron USA | (631) 858-8400 | www.tamron.com
Tokina (THK Photo Products) | (800) 421-1141 | www.thkphoto.com
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