Something For Everyone
the overwhelming popularity of digital SLR cameras, it's understandable
that all lens manufacturers are devoting their resources to this market. All
of the new products--featuring entirely new designs--shown during
PMA 2005 were exclusively for use with digital SLRs that employ the APS-C size
sensor; these are not suitable for use with film-based cameras. (Vignetting
will occur if such a lens were used on a 35mm camera or a digital SLR with a
Owners of other types of cameras could not complain about being ignored, because Sigma unveiled 10 multi-platform lenses upgraded to the DG (Digitally Optimized) standard. They're not "entirely new" however, because they incorporate the same optical designs as the previous incarnations of the same products. The significant difference is the addition of superior multilayered coatings to more elements, as discussed later.
The new "Digitally Optimized" Sigma lenses are all telephotos, either prime or zoom. They include the following
multi-platform models: APO 50-500mm f/4-6.3 EX, APO 70-200mm f/2.8 EX, APO 80-400mm f/4.5-5.6 EX OS (with Optical Stabilizer), APO 100-300mm f/4 EX, APO 120-300mm f/2.8 EX, APO 300-800mm f/5.6 EX, APO 180mm f/3.5 EX, APO 300mm f/2.8 EX, APO 500mm f/4.5 EX, and APO 800mm f/5.6 EX. All of these products benefit from the latest
anti-reflective technology in order to compensate for the increased risk of flare with digital cameras' highly reflective (almost mirror-like) sensor chips. Naturally, the DG series should provide higher contrast and greater resistance to flare and ghosting in extremely bright conditions, regardless of the type of camera used. (Prices not yet set.)
Wide Angle And "Normal" Lenses
All of the other new entries were designed exclusively for use for digital cameras with the APS-C size sensors. The lenses are smaller because they must cover an image circle that's smaller than a 35mm film frame. Hence, they're also lighter in weight than the comparable multi-platform lenses that provide equivalent focal lengths in film-based photography. Some, but not all, are also less expensive than the comparable multi-platform lenses; they're not cheap because of the extra high-tech optical elements required for the full correction required in digital photography.
Particularly short focal length lenses benefit from new optical designs and technology, as mentioned in my coverage of each new lens. For a detailed discussion of the entire issue relating to lenses for digital SLRs, review our article on Digitally Optimized Lenses in the March 2005 issue; it's also available on the shutterbug.com website, easily found using the Search feature.
The shortest zoom in the Tamron line, the new SP AF11-18mm f/4.5-5.6 Di-II
LD Aspherical (IF) zoom (exclusively for digital SLRs) is roughly equivalent
to a 17-28mm zoom in 35mm terms. (For exact focal length equivalents for any
lens, multiply by the appropriate magnification factor, such as 1.5x or 1.6x.)
This zoom was designed to ensure that all light rays strike the image sensor
at an optimum angle for even edge to edge brightness.
Special multilayered coatings on numerous elements minimize internal flare and ghosting that can be caused by a highly reflective CCD or CMOS sensor. The optical formula is impressive, too, including a glass-molded aspherical element, hybrid aspherical elements, plus elements of high index/high dispersion as well as low dispersion glass, intended to produce the best possible results. This zoom is quite compact for an ultra-wide with a length of 3.3" and 77mm size filters. It's available in Canon AF, Konica Minolta AF-D, and Nikon AF-D mounts. (Estimated street price: $549.)
Sigma's shortest zoom, the new 10-20mm f/4-5.6 EX DC HSM, is part of the DC ("Digital Capture") series so it benefits from superior multilayered coatings as well as other technology to ensure even brightness and sharpness across the frame. Designed to provide an ultra-wide angle of view with Sigma, Canon, or Nikon digital SLRs, the optical formula includes three Special Low Dispersion (SLD) elements plus three aspherical lens elements for outstanding image quality. Other features include a non-rotating lens barrel for great convenience when using a (77mm) polarizer and ultrasonic HSM focus motor. The latter provides high speed, nearly silent autofocus performance as well as manual focus override without the need to switch out of autofocus mode. (Estimated street price: $649.)
THK Photo Products, Inc. has also entered the market with the first Tokina
DX-series zoom designed exclusively for digital SLRs. The AF 12-24mm f/4 AT-X
Pro DX zoom features a wide, constant maximum aperture great for low-light focusing
and shooting. Surprisingly, this fast zoom is not much larger than the variable
aperture ultra wides (3.3" long, 77mm filter size), although its 3.5"
diameter is greater than the 3.1" average and it's a bit heavier.
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