Instead, the best way to choose a camera is to evaluate each system (body, lens, flash). The aspects of the system other than the body (lenses and flashes), have qualities, features, availability and prices that change less often than do the features in bodies.
Below is a comparison between major manufacturers (alphabetical order), intended primarily for family photographers. Here's some background explanation:
- Crop factor: This is the multiplier to make the sensor equivalent in size to traditional 35mm film. For example, a crop factor of 2x means the sensor needs to be enlarged 2x to be the same size as 35mm. This is important for two reasons: 1. The larger the crop factor, the smaller the sensor, and usually, smaller sensors are less sensitive to light than larger sensors of the same generation. 2. When comparing lenses, you need to multiply the focal length with the crop factor to determine the equivalent focal length in 35mm terms. A higher crop factor means you get a longer effective telephoto but also wide angle lens with less effective width. If there are two crop factors shown below, it means the manufacturer produces bodies with smaller sensors and those with larger sensors. Lenses for larger sensors can be used for smaller sensor bodies (often with better image quality) but not vice-versa.
- Wide zooms: have a field of view that is wider than normal human vision. Useful for environmental portraits, tight spaces (like small rooms), landscape or architecture shots, and for exaggerating perspective.
- Standard zooms: have a field of view and perspective that is about the same as normal human vision (50mm in 35mm terms). For 35mm film, a useful zoom range for this was 24-70, and some manufacturers have made equivalent lenses for smaller sensors.
- Telephoto zooms: have a field of view that is narrower than normal human vision, and presents a closer view of the subject. Useful for sports photos, wildlife photos, portraits, and events where the action is far away. For 35mm film, a useful zoom range for this was 70-200, and some manufacturers have made equivalent lenses for smaller sensors.
- Superzoom lenses: have a very wide zoom range. Useful as a do-it-all lens, with limitations on image quality.
- Wide aperture lenses: lenses with a wide aperture are useful for getting a shallow depth of field and for taking photos in low-light environments without flash.
- Pancake lens: a relatively flat/short lens. Useful for maintaining a low-profile when shooting and for portability.
- Pro vs. Consumer lenses: the usual differences are in price (pro lenses are usually in the four figures), build quality, image quality (resolution, contrast, colors), constant aperture, image stabilization, and size. But this doesn't preclude consumer lenses that can produce good image quality.
- Image stabilization: technology that adjusts the lens or sensor to compensate for the photographer's movement. Allows sharper shots with a slower shutter speed. Called differently by each manufacturer (Canon: IS - image stabilization; Nikon: VR - vibration reduction; Olympus: Image Stabilization; Panasonic: OIS - Optical Image Stabilization; Pentax: SR - shake reduction; Sony: SteadyShot; Sigma: OS - optical stabilization; Tamron: VC - vibration compensation).
- Flash: on camera, almost all flashes perform identically. Flash systems differ, however, with respect to their wireless capabilities. This is important for lighting control.
- Strengths: I researched the reasons users switch to the system, and what users often cite as the advantages of the system. I gave greater weight to opinions of pros.
- Weaknesses: I researched the reasons users switch away from the system, and what users complain about the system. I gave greater weight to opinions of pros. To avoid World War III, I did not include criticisms of the system by users of other systems.
Crop factor: 1.6x, 1.25x, 1.0x
Pro: 16-35 2.8 ($1420)
Consumer: 10-22 ($720); Tokina 11-16 2.8 ($900); Tokina 12-24 f/4 ($500)
Pro: 17-55 2.8 IS ($1110); 24-70 2.8 ($1300)
Consumer: 17-85 IS ($440), Tamron 17-50 2.8 ($499), Tamron 17-50 2.8 VC ($650), Tamron 28-75 2.8 ($460)
Tele zooms: Pro: 70-200 2.8 IS ($2500); 70-200 2.8 ($1210)
Consumer: 70-200 f/4 ($1129); sigma 50-150 2.8 ($749)
Superzoom: 18-200 IS ($600)
Wide aperture lenses: 50 1.2 ($1500); 50 1.4 ($345); 50 1.8 ($100); 85 1.2 ($1870); 85 1.8 ($380)
Flash: wireless ratio control (user remotely changes the ratio between up to 3 flash groups). Canon 7D popup flash can be used as commander. Other cameras require ST-E2 or an external flash as commander.
Strengths: widest selection of high quality lenses (especially telephoto); color
Weaknesses: reliability (see comment 20 here), autofocus issues (some), no pancake lens
NIKON (and Fujifilm DSLRs)
Crop factor: 1.5x, 1.0x
Pro: 14-24 2.8 ($1800)
Consumer: 10-24 ($806); Tokina 11-16 ($615); Tokina 12-24 ($460)
Pro: 17-55 2.8 ($1520); 24-70 2.8 ($1704)
Consumer: 16-85 VR ($630), Tamron 17-50 2.8 ($460), Tamron 17-50 2.8 VC ($635), Tamron 28-75 ($460)
Pro: 70-200 2.8 VR ($2240);
Consumer: 80-200 2.8 ($1100); 70-300 VR ($537); sigma 50-150 ($749)
Superzoom: 18-200 VR ($741)
Wide aperture lenses: 35 1.8 ($200); 50 1.4 ($330); 50 1.8 ($125); 85 1.4 ($1230)
Flash: wireless flash adjustment (user remotely selects manual or TTL or Auto flash exposure, user adjusts output or flash exposure compensation); popup flash can be used as commander in mid-level and pro bodies.
Strengths: flash system (and wireless flash capabilities); handling
Weaknesses: some lenses more expensive than Canon equivalent; fewer lenses than Canon; no pancake lens
OLYMPUS / PANASONIC (FOUR-THIRDS)
Crop factor: 2x
Wide zooms: Olympus 9-18 ($475); Sigma 10-20 ($469)
Pro: Olympus 14-35 f/2 ($2000)
Consumer: 14-54 ($500)
Pro: Olympus 35-100 f/2 ($2300)
Consumer: Olympus 50-200 ($980)
Wide aperture lenses: Sigma 24 1.8 ($449); Panasonic 25 1.4 ($1066); Sigma 30 1.4 ($439), Sigma 50 1.4 ($499), Olympus 50 f/2 ($454)
Flash: wireless flash adjustment beginning with FL-50R and FL-36R, and with Olympus x20 series and above (420, 520, 620, etc.) (user remotely selects manual or TTL or Auto flash exposure, user adjusts output or flash exposure compensation); popup flash can be used as commander with Olympus x20 series and above.
Strengths: smaller size of bodies and lenses; f/2.0 zooms (which would be too large and expensive on other systems); pancake lenses; built-in image stabilization; deeper depth of field
Weaknesses: limited lens selection, limited third-party support, deeper depth of field.
OLYMPUS/PANASONIC (MICRO FOUR-THIRDS)
Note: Micro 4/3 is similar to 4/3 in that they both have the same sensor size. However, the m4/3 lenses are not compatible with 4/3 bodies, and vice-versa (4/3 lenses can be used on m4/3 bodies with an adapter and with the same limitations as using a lens of a different system).
Crop factor: 2x
Pro: Panasonic 7-14 f/4 ($1100)
Consumer: Olympus 9-18 ($680)
Standard zooms: Olympus 14-42 ($254)
Tele zooms: Panasonic 45-200 ($310)
Superzoom lens: Panasonic 14-140 OIS ($816) Panasonic 14-150 OIS ($1450), Olympus 14-150 ($600)
Wide aperture lenses: Olympus 17 2.8 ($231); Panasonic 20 1.7 ($362)
Flash: wireless TTL flash on some bodies (currently Olympus E-PL1)
Strengths: smallest bodies; built-in image stabilization, video capabilities of some bodies; deeper depth of field
Weaknesses: very limited lens selection (for now), limited third-party support, deeper depth of field.
PENTAX and SAMSUNG
Crop factor: 1.5x
Pro: 12-24 f/4 ($700)
Consumer: 10-17 ($500)
Pro: 16-50 2.8 ($700)
Consumer: Tamron 17-50 2.8 ($489); 17-70 f/4 ($480)
Pro: 50-135 2.8 ($1129); 60-250 f/4 ($1204)
Consumer: sigma 50-150 ($749)
Wide aperture lenses: 31 1.8 ($980); 55 1.4 ($677)
Flash: non-adjustable wireless triggering (up to 2 groups in a fixed 3:1 ratio).
Strengths: many good prime lenses; best exposure controls in the industry (hyper manual, hyper program, TAv priority, Sensitivity priority); built-in image stabilization; bodies usually have more features for price; compatibility with older lenses; pancake lenses
Weaknesses: although focus is accurate, acquiring focus is slower than in other systems. Limited telephoto lens selection. Limited third-party support. No wireless adjustment of flash exposure. No full frame body (but the medium format 645D is being released in Japan).
Crop factor: 1.5x, 1.0x
Wide zooms: 11-18 ($650)
Pro: Zeiss 24-70 2.8 ($1600)
Consumer: 16-80 ($700); Tamron 17-50 2.8 ($460); 28-75 2.8 ($700)
Pro: 70-200 2.8 ($1800)
Consumer: sigma 50-150 2.8 ($749)
Wide aperture lenses: 35 1.4 ($1200); 50 1.8 ($149); zeiss 85 1.4 ($1283)
Superzoom: 18-250 ($580)
Flash: wireless ratio control beginning with a700 and a900 (requires HVL-F58AM as controller on camera). Proprietary flash hotshoe.
Strengths: sensor technology, built-in image stabilization, zeiss lenses, bodies usually have more features for price
Weaknesses: limited lens selection. Limited third-party support. Proprietary flash hotshoe limits third party accessories.
As for me? I initially went with Pentax because I liked the image stabilization and the low noise of the K100D. The problem was that the Pentax took longer to acquire focus, causing me to miss shots of our baby as he became more mobile. So after about a year, I switched to Nikon because of the wireless flash capabilities. I've been with Nikon for two years now with no regrets so far. I may get a Tokina 11-16 or Tokina 12-24 to cover ultra wide angle. In the future, when our kid grows up and gets into sports, I may get a 4/3 body with a telephoto lens like the Olympus 50-200 2.8-3.5 to supplement my main camera (due to the 4/3 system's 2x crop factor, lenses have longer effective focal length -- the 50-200 is equivalent to 100-400). There's no rule against having more than one system :).