Sigma Camera Lens CAN 35MM User Manual

Lens Compatibility with Digital SLR Cameras  
CAN 35MM SLR LENSES BE USED ON DIGITAL CAMERAS?  
In most cases, the answer is yes. If you have a lens for a fairly recent 35mm SLR camera, it can be used on a  
new digital SLR from the same maker. (See the information below under the various camera brands for specific  
details about using existing lenses on new cameras.) If the 35mm camera lens produces good, sharp, contrasty  
images on film, it will produce good digital photos, too. One big difference is the angle of view. The imaging sen-  
sor in most digital cameras is smaller than 35mm film, measuring about 23 x 16mm. Therefore, wide-angle lens-  
es for 35mm camera are not as wide when used on a digital camera, but telephoto lenses are stronger. With  
35mm cameras, a 50mm lens is the “normal” focal length that gives you about the same view as the human  
eye. Below 50mm, the view gets wider, above 50mm it becomes telephoto and draws the subject in closer. For  
digital cameras, this “normal” focal length is about 32mm, so an old 50mm lens from your 35mm camera will be  
a short telephoto (equal to 80mm) when used on a digital. An 18-200mm zoom lens for a digital camera has  
about the same wide coverage and telephoto magnifying power as a 28-300mm lens on a 35mm camera. To  
convert the equivalent view of a 35mm lens when used on a digital camera, multiply by 1.6X.  
A few high-end digital cameras, such as the Canon EOS 1Ds and EOS 5D have full-frame sensors. Since these  
sensors match the 24mm x 36mm size of 35mm film, there is no conversion factor when they are used with  
35mm lenses.  
LENS CONVERSION FOR VARIOUS CAMERA FORMATS  
Extreme Wide Wide Angle  
97 degrees AOV 75 degrees AOV 46 degrees AOV 27 degrees AOV 12 degrees AOV  
Normal  
Short Tele Moderate Tele  
Digital SLR  
(1.6X factor)  
12mm  
19mm  
18mm  
28mm  
50mm  
32mm  
50mm  
80mm  
56mm  
90mm  
128mm  
200mm  
35mm Film  
6x6cm Film  
40mm  
(88 deg.)  
150mm  
(30 deg.)  
350mm  
(13 deg.)  
AOV = angle of view  
6x6cm = 2-1/4 x 2-1/4" format on 120 film  
DIGITAL-ONLY LENSES  
Since the future of SLR photography is digital and since most digital cameras have sensors that are smaller  
than 35mm film, manufacturers are making digital-only lenses. The primary difference is the reduced area of  
coverage provided by digital-only lenses. These lenses have the same mounting style as 35mm format lenses  
and they can be mounted on 35mm camera bodies (except Canon EF-S lenses), but they will not cover the full  
image size. This causes vignetting around the edges of the 35mm image, especially at the widest end of the  
lens zoom range.  
 
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  
 

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