Canon Rebel XTi vs. Nikon D80 vs. Sony Alpha A100 Head-to-Head-to-Head Digital Camera Review

Metering (Advantage: Sony Alpha A100)
Learning how the various metering patterns work is a significant part of getting the hang of a new camera. Though the general descriptions of various metering patterns are the same from camera to camera, their function varies significantly.

The Sony Alpha A100, the Nikon D80, and the Canon Rebel XTi all have evaluative and center-weighted modes, and both the D80 and the Alpha have spot modes, while the XTi has a "partial" metering mode, which is more or less a very large spot. Nikon sweetens the deal by allowing the user to choose a 6, 8 or 10 mm zone for the center-weighted area. The smallest zone behaves quite a bit like the Rebel XTi's partial mode. The D80's spot mode can be set to take its reading at the active autofocus site. The Sony Alpha's spot zone is at the center of the frame.
 

Sony A100



Nikon D80



Canon XTi

Evaluative metering systems measure a number of areas of the frame separately, and use a logic system to arrive at an exposure. The systems are supposed to detect tricky lighting situations, such as backlighting, or unusually dark backgrounds. The idea is that they'll identify the subject, and optimize exposure for it. All three cameras rely on their evaluative metering systems in their automated modes.

We shot a backlit scene at various zoom settings with each camera, and shot our GretagMacbeth chart on a black background, framing it at the center of the frame and off-center with each camera. It's typical that test shots such as these don't look ideal – the subject looks a little too dark in the backlit shot, and a little too light when shot with a black background. In this comparison, however, the Sony Alpha 100 performed notably better at both tests than the Nikon D80 or the Canon Rebel XTi. The Alpha's shots retain bright colors in the subject of the backlit scene, and keep the black background truly dark in the other scene. By comparison, the Canon and Nikon look inadequate, although the Nikon’s more versatile interface provides users with more room for adjustment.

Sony A100

Nikon D80

Canon XTi

Focus (Advantage: Nikon D80)
The Sony Alpha A100 and the Canon Rebel XTi each have 9 autofocus sensor sites, and the Nikon D80 has 11. The comparison might strike fans of "This Is Spinal Tap" as a distinction without a substantial difference. The Nikon has a real advantage, though. The D80's sensors are spread further across the frame, and are arranged in a rectangle of nine sensors, with one more on either end. Shooting either horizontals or verticals, it's easy to get a critical part of the subject under one of the sensors. The XTi's sensors are set in a diamond pattern, concentrated toward the middle of the frame. That's a disadvantage for many common shots of people – the sensors end up on the subject's chest more often than on his/her face. The Sony Alpha's sensors don't span as much of the screen as the D80's, but the outer 4 are at the corners of a rectangle, which is convenient for horizontals of groups of people. The default sensor is at the center of the frame, and 4 more are around the center, above, below and to either side, but close to the center. All three cameras will automatically choose the autofocus sensor, or allow the user to set it. The Sony has an advantage for manual selection – the user can press the 4-way controller ring anywhere around its circumference to jump directly to the corresponding sensor site. The Nikon also uses the 4-way controller to navigate sensor sites, but the user has to move one site at a time, pressing the controller for horizontal and vertical moves separately. The Canon is more cumbersome:; the user must press a button while turning the control dial to move from the center and around the ring of sensors.

All three cameras focused accurately in bright light. We found the D80 more sensitive than the Alpha or the XTi in low light, and had an easier time following moving subjects with the Nikon as well.

All three cameras allow manual focus, and their manuals suggest using it with subjects that autofocus can't handle. We found the Sony Alpha A100 screen problematic for manual focus with the provided lenses – it's dark, and hard to see focus through the viewfinder. The Canon and Nikon were better, but they were also limited by their kit lenses, which have relatively small maximum apertures. We found the D80 easy to focus with a 35mm f/2.0 lens. Logically, both the Sony and the Canon should perform their best with bright lenses as well.

Exposure (Advantage: Draw)
There are two fundamental qualities most photographers want in-camera exposure systems. First, cameras should set the ideal average exposure in situations where they can be set to automatic. Second, they should behave predictably in situations where the photographer uses manual controls. Our exposures with the three cameras included some general shooting as well as our test shots. We found that the Canon Rebel XTi consistently recorded images a bit lighter than the Nikon D80 or the Sony Alpha A100, which were quite similar. Typically, all three cameras set the same exposure of a given scene, but the levels in the image from the XTi were brighter. The difference is less than 1/3 EV, but it's perceptible.