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Perhaps the most backward-compatible camera brand, a new Pentax digital SLR camera will accept a lens
made for one of the first Pentax K bayonet-mount 35mm cameras back in the mid-1970s. If the lens has auto
aperture control (Pentax KA) and autofocus (Pentax KAF) capability, those features will couple to the D-SLRs
controls. A Pentax digital SLR will even accept old Pentax screw-mount lenses made for cameras in the 1960s
and early ‘70s, provided a Pentax Lens Mount Adapter B is used.
Pentax is now collaborating with Samsung on digital SLR design, so present (and most likely, future) Samsung
digital SLR cameras use the same lens mounting system as Pentax.
OLYMPUS
Unlike the other 35mm camera brands, Olympus was never successful with their 35mm autofocus SLR system
so they didn’t have a legacy lens system to use with digital SLR cameras. Thus they created a new lens system
open to other camera makers as well, called the Four Thirds system, after the 4:3 aspect ratio of the sensors
used by Olympus D-SLRs. The size of sensors used in Olympus D-SLR cameras measure 17.3 x 13mm, much
larger than commonly used in “point & shoot” style cameras, but smaller than the approximately 23 x 16mm
sensors used by other D-SLR makers. One significant difference is Olympus focal lengths are one-half the
equivalent of 35mm format lenses (a 2X factor) for the same field of coverage. So a new 25mm lens is equal in
view to a 50mm lens on a 35mm camera, a 14mm wide-angle is equivalent to a 28mm film camera lens, etc.
These lenses are designed specifically for digital SLR cameras.
Olympus made an earlier manual-focus 35mm camera system called the OM system. While Olympus makes a
lens mount adapter to attach OM lenses onto their D-SLR cameras, there is a significant loss of features.
INDEPENDENT LENS MAKERS
Lenses made by independent lens makers usually have the same compatibility characteristics as camera-brand-
ed lenses. For instance, a Tamron lens made for a Canon EOS film camera will work on a Canon digital camera
in the same manner as a Canon brand lens. Independent lens makers have often kept mechanical aperture
rings on Nikon and Pentax-mount lenses long after those two camera makers have dropped them from all but
select series of lenses.
TAMRON
Tamron’s latest generation of lenses is called the Di-II series. These digital-only lenses cover digital sensors,
without the covering power needed for film. Tamron also has Di lenses that will cover film and digital formats
and they have been optimized in their design and multi-coatings to perform better on digital cameras than earlier
lenses made only with film photography requirements in mind.
SIGMA
Sigma makes several lines of lenses, with DC format lenses their digital-only line. Sigma’s DG lenses are opti-
mized for better performance with digital cameras, but will work fine with 35mm cameras and will cover the full
image size.
TOKINA
Pro DX lenses from Tokina are digital-only and won’t cover full size sensors or 35mm film. Some Tokina lenses
are designated ProD and will work fine for both film and digital cameras and have the improved multi-coatings
for excellent digital performance.
Courtesy of Porter’s Camera Store
Phone: 1-800-553-2001
www.porters.com