You don't need a "full-frame"-sensor D-SLR to do wide-angle photography
By Mike Stensvold
APS-C Lens Main Advantages
Wide-angle capability with APS-C sensor D-SLRs
Optimized specifically for APS-C sensors
APS-C Lens Disadvantages
Can't be used on 35mm or "full-frame" D-SLRs
Diffraction can reduce image quality at the smallest aperture settings
Tip For The Budget-Minded The really wide-angle zoom lenses for smaller-sensor D-SLRs start around $500. If you're on a tight budget and want wide-angle capability, check out the "standard" zooms often sold with these cameras. These 18-55mm (or thereabouts) lenses sell for under $200 (closer to $100 if purchased in a kit with the camera body), and that 18mm focal length is equivalent to 27mm on a 35mm SLR—definitely wide-angle
A full 35mm film frame measures 36x24mm, an area of 864 square millimeters. An APS-C image sensor measures 23.6x15.8mm (or thereabouts, depending on the camera), an area of just 373 square millimeters. The much smaller APS-C sensor, "sees" a lot less of the image projected at the image plane than a full 35mm film frame (or a "full-frame" digital image sensor) sees. The result? Any given lens used on a D-SLR with a smaller sensor frames as a lens that’s about 1.5x its focal length does on a 35mm camera: a 28mm wide-angle lens effectively becomes a 42mm not-so-wide one when attached to the D-SLR.
Put another way, with an APS-C-sensor D-SLR, you need a focal length 33% shorter to get the same field of view that a given lens yields when attached to a 35mm SLR. If you want the angle of view a 24mm lens provides on a 35mm SLR, you need a 16mm lens on the D-SLR.
Camera manufacturers Canon, Nikon, Olympus, Pentax, Sigma and Sony all offer very short focal-length zoom lenses for their small-sensor D-SLRs. Fujifilm and Samsung don’t make lenses for D-SLRs, but their D-SLRs accept Nikon lenses and Pentax lenses, respectively.
Four Thirds System D-SLRs use even smaller 17.3x13.0mm image sensors, with a 2x focal-length factor. Olympus provides two very short focal-length zooms for Four Thirds System cameras, which include all Olympus D-SLRs, plus the Leica Digilux 3 and Panasonic Lumix DMC-L1.
But wait, there’s more. Independent lens makers Sigma, Tamron and Tokina produce very short focal-length zooms in mounts for many of these cameras, and Sigma’s also will fit Sigma D-SLRs. Thus, users of all current D-SLR models can do true wide-angle photography, regardless of the size of their camera’s image sensor.
Focal-Length Equivalency Table
If you want the field of view of this focal length a on a 35mm SLR
Use this focal length on a D-SLR with a 1.5x factor
Use this focal length on a D-SLR with a 1.6x factor
Use this focal length on a D-SLR with a 1.7x factor
Use this focal length on a D-SLR with a 2.0x factor
You can see from this table that you need a focal length of 18mm or shorter to get a really wide-angle effect with a smaller-sensor D-SLR.
These very short focal-length zooms offer benefits beyond providing true wide-angle shooting capability with smaller-sensor cameras. They also were designed specifically for the APS-C-sized image sensor (Four Thirds System lenses were designed specifically to work with the Four Thirds System image sensor). Since they don’t have to cover as large an area at the image plane, these lenses can be more compact than those designed to provide the same angle of view for a full 35mm film frame.
There are a few drawbacks, however. APS-C lenses can be used only on APS-C cameras—if you use them on a full-frame D-SLR or a 35mm SLR, they’ll vignette because they weren’t designed to cover such a large image area; and in some cases, they can’t physically be mounted on full-frame cameras. And because of their very short focal lengths, diffraction can adversely affect image sharpness at small apertures—ƒ/22 on a 10mm lens is just 0.45mm (1/56-inch) in diameter. Of course, the shorter focal lengths yield more depth of field, so there’s seldom a need to stop all the way down to ƒ/22.
WIDE-ANGLE ZOOM LENSES FOR D-SLRS
Filter Size (mm)
Elements/ Groups (special elements)
Min. Focus (in.)/Magnif.
Diameter & Length (in.)
Pentax smc-P-DA 10-17mm ƒ/3.5-4.5 ED-IF Fisheye
Tokina AT-X 10-17mm ƒ/3.5-4.5 AF DX Fish-Eye
Canon EF-S 10-22mm ƒ/3.5-4.5 USM
13/10 (SUD, Asp)
Nikon 12-24mm ƒ/4G ED-IF AF-S DX Zoom-Nikkor
11/7 (ED, Asp)
Pentax smc-P-DA 12-24mm ƒ/4.0 ED/AL (IF)
13/11 (ED, Asp)
Sigma 10-20mm ƒ/4-5.6 EX DC
14/10 (SLD, Asp)
Sony SAL 11-18mm ƒ/4.5-5.6 DT
15/12 (ED, Asp)
Tamron 11-18mm ƒ/4.5-5.6 Di II LD Aspherical (IF)
15/12 (LD, Asp)
Tokina 12-24mm ƒ/4 AT-X AF PRO DX
13/11 (SD, Asp)
For Four Thirds System
Olympus 7-14mm ƒ/4.0 Zuiko Digital
18/12 (SED, ED, Asp)
Olympus 11-22mm ƒ/2.8-3.5 Zuiko Digital
Notes This is a sampling of wide-angle zoom lenses, not necessarily a complete list ED, LD, SD, SED, SLD and SUD are low-dispersion elements; see text APS-C format indicates a lens designed for use with D-SLRs having APS-C-size image sensors; can't be used with full-frame sensors or 35mm SLRs 4/3 format indicates a lens designed for use with Four Thirds System D-SLRs n/a = information not available at press time
So which are the APS-C lenses? The accompanying Wide-Angle Zoom Lenses For D-SLRs chart lists the current ones. You also can identify APS-C lenses by the code each manufacturer uses for those lenses that were designed specifically for use with the smaller-sensor D-SLRs: DA (Pentax), DC (Sigma), Di II (Tamron), DT (Sony), DX (Nikon and Tokina) and EF-S (Canon). Lenses with these designators can’t be used with film cameras or full-frame-sensor D-SLRs because vignetting would occur.