Small-Format Wide-Angle Zooms

You don't need a "full-frame"-sensor D-SLR to do wide-angle photography

By Mike Stensvold

The Problem

APS-C Lens Main Advantages

Wide-angle capability with APS-C sensor D-SLRs
Optimized specifically for APS-C sensors
Relatively compact

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.

The Solution

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
15mm	10mm	9.4mm	8.8mm	7.5mm
18mm	12mm	11.2mm	10.6mm	9mm
20mm	13.4mm	12.5mm	11.8mm	10mm
24mm	16mm	15mm	14mm	12mm
28mm	18mm	17.5mm	16.5mm	14mm
35mm	24mm	22mm	20.6mm	18mm
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.

A Bonus

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
Lens	Filter Size (mm)	Elements/ Groups (special elements)	IF/Rear Focusing	Format	Min. Focus (in.)/Magnif.	Diameter & Length (in.)	Weight (oz.)	List Price
Fisheye Zooms
Pentax smc-P-DA 10-17mm ƒ/3.5-4.5 ED-IF Fisheye	none	10/8 (ED)	IF	APS-C	5.5/1:2.6	2.7x2.8	11.3	$541
Tokina AT-X 10-17mm ƒ/3.5-4.5 AF DX Fish-Eye	none	10/9 (SD)	n/a	APS-C	5.5/1:2.6	2.8x2.8	12.3	$535
Wide-Angle Zooms
Canon EF-S 10-22mm ƒ/3.5-4.5 USM	77	13/10 (SUD, Asp)	IF	APS-C	9.6/1:4.2	3.3x3.5	13.6	$775
Nikon 12-24mm ƒ/4G ED-IF AF-S DX Zoom-Nikkor	77	11/7 (ED, Asp)	IF	APS-C	11.8/1:8.3	3.2x3.5	17.1	$1,099
Pentax smc-P-DA 12-24mm ƒ/4.0 ED/AL (IF)	77	13/11 (ED, Asp)	IF	APS-C	12/1:8.3	3.3x3.4	15.2	$710
Sigma 10-20mm ƒ/4-5.6 EX DC	77	14/10 (SLD, Asp)	IF	APS-C	9.4/1:6.7	3.3x3.2	16.6	$473
Sony SAL 11-18mm ƒ/4.5-5.6 DT	77	15/12 (ED, Asp)	IF	APS-C	9.6/1:8	3.3x3.2	12.7	$649
Tamron 11-18mm ƒ/4.5-5.6 Di II LD Aspherical (IF)	77	15/12 (LD, Asp)	IF	APS-C	9.8/1:8	3.3x3.1	12.5	$490
Tokina 12-24mm ƒ/4 AT-X AF PRO DX	77	13/11 (SD, Asp)	IF	APS-C	11.8/1:8	3.3x3.5	20.1	$450
For Four Thirds System
Olympus 7-14mm ƒ/4.0 Zuiko Digital	none	18/12 (SED, ED, Asp)	n/a	4/3	9.75/1:9.1	3.4x4.7	27.9	$1,594
Olympus 11-22mm ƒ/2.8-3.5 Zuiko Digital	72	12/10 (Asp)	no	4/3	11.0/1:7.7	2.9x3.6	17.1	$720
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.

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