Comparison of the Canon Rebel XSi, XTi and EOS 40D

Whenever a new camera is released the inevitable question is "Should I get A, B or C", or sometimes "Should I upgrade from A to B"? Well, this time is no different. I'm sure there will be lots of people asking "Should I get a Rebel XTi, XSi or 40D" or "Should I upgrade from my XTi to an XSi or an EOS 40D"?

Everything really depends on what you shoot, how you shoot, and, of course, how much money you have!

The first and most obvious thing that the new Rebel XSi has and the Xti and EOS 40D don't is a 12MP sensor. The other two are 10MP, so how much difference will that make. The most likely answer is "not very much". Going from 8MP (EPOS 20D) to 10MP (EOS 40D) results in a barely discernible increase in image resolution. You can see it if you look really closely, but it's not a big deal. The jump from 10MP to 12MP is smaller (+20%) than the jump from 8MP to 10MP was (+25%), so for the most part it won't be a significant difference.

The downside of more pixels is that they must be smaller to fit on the same sized sensor, and smaller pixels typically result in higher noise levels. Of course improvements in electronics and signal processing can compensate for this to some extent. We'll only know for sure when we see actual tests, but my gut feeling is that the noise level in the XSi will probably be very close to that of the XTi

Comparison of the Rebel XTi, XSi and EOS 40D

The areas in bright blue show where a particular camera has an advantage. Not every camera feature is show, only those where there is a difference between the cameras. All three share many common features in terms of exposure modes, white balance, bracketing etc. All three have 9 zone AF for example, though it's possible the AF systems may have different performance. Only time (and testing) will tell.

It's pretty clear from this comparison table that the XSi is closer to the EOS 40D than it is to the XTi. Besides the hardware features, both cameras share a very similar menu interface and set of custom features.

So what's the conclusion? Well, just as in the past, I think the image quality from the XSi will be pretty close to that of the EOS 40D and XTi, just as the image quality of the XTi, EOS 20D, EOS 30D and EOS 40D aren't too far apart either. Where the 20D/30D/40D are "better" than the XT/XTi/XSi are mainly areas of ergonomics, durability and compatibility with accessories. For example the EOS 40D has a rear QCD (Quick Control Dial) as well as the usual dial to set camera parameters. What this does is allow you to quickly change settings (such as exposure compensation or aperture/shutter speed in manual mode), without having to press any extra buttons. It doesn't affect image quality, but it does improve the camera handling.

The Rebel XSi can autofocus in Live View mode without dropping the reflex mirror down, which could be useful, though to do that it uses contrast detection (rather than phase detection), which is slower (and possibly less accurate). I'm not sure that Live View should be thought of a s a"normal" shooting mode, the way it is with most P&S digicams. The larger sensor draws more power, which shortens battery life and heats up the sensor more. As the sensor warms up the noise increases.

The 40D is compatible with higher level cameras such as the EOS 5D and 1D(s) series cameras in terms of batteries and memory cards, as well as sharing common accessories such as the remote release cable, wireless transmitter etc. Obviously if you're looking for a backup camera, this can be important. The Rebel cameras use a different battery, a different remote release and aren't compatible with some of the more advanced accessories such as the WFT-E3A wireless transmitter.

Like other cameras in the Rebel series, the XSi is limited to ISO 1600. For some users the ability to go to ISO 3200 with the 40D could be very important. For other users, who don't do low light photography, it may be a matter of no consequence at all. It depends what you shoot and when you shoot it.

Conclusions

Obviously I haven't yet had a chance to try the new Canon EOS Rebel XSi, and so I can't offer more than an informed opinion at this point. However I'd say the new XSi looks like a real improvement over the XTi in terms of features and usability. Image quality will probably be quite similar. For someone upgrading from a P&S digicam it looks like a very good camera, and that fact that it uses SD cards (which most P&S digicams also do these days) could be a plus. The EF-S 18-55/3.5-5.6 IS kit lens is getting excellent reviews and since it only costs $100 when bought with the XSi, that makes a nice, image stabilized starter package.

For someone upgrading from an XTi, the choice is s little more difficult. If that person was very happy with the XTi, there's really no reason not to chose the XSi. If they were a little frustrated at times by the limitations of the XTi ergonomics, then looking at an EOS 40D might make sense. The price on the EOS 40D has dropped from an initial $1300 to around $1150 now, which only makes it $350 more than the price you'll have to initially pay for a Rebel XSi ($799.99). I think the 40D is probably the better buy for the more serious photographer who shoots a lot. The EOS 40D is probably more durable, though the Rebel bodies seem to be durable enough - I've not really heard any recent complaints about them failing due to the use of more plastic parts (though there was a problem with the plastic hinge on the mirror of early 350Ds which was later replaced by a metal part).

Of course if you want a camera NOW (and I'm writing this in late January 2008), and the XTi doesn't meet your needs, then the EOS 40D is your obvious choice since the Rebel XSi won't start shipping until mid-April. You'd probably have a 3 month wait before actually getting your hands on one! The XTi isn't a bad choice either if you're just moving up from a P&S digicam. You can get it now without having to wait and the price of the XTi + 18-55 kit lens is currently around $580, which is significantly less than the new XSi will be when it's available. If you do decide you want the new XSi as soon as it's available, then it's a good idea to place a pre-order. There's no charge until it ships and you should be first on the list when distribution starts.