Canon XTi Performance

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Canon Rebel XTi Performance

The Canon XTi proved to be a pretty responsive camera in our tests. Startup was pretty fast at 0.4 seconds; albeit not quite up to the fastest we've seen, but certainly quick enough that you're unlikely to lose any critical shots. Shutter lag was low, and shot-to-shot cycle times in both single-shot and continuous mode were very good. It's not up to the speeds of some of Canon's big, burly professional SLRs, but it competes well with consumer DSLR models in its price range, and should be more than adequate for most amateur shooting. Read on below for all the details:

Timing and Performance

Very good speed for a digital SLR.

Startup/Shutdown
Power on to first shot	0.4 / 2.5 seconds	Power on time / including sensor cleaning
Shutdown	0.1 / 1.6 seconds	Shutdown time / including sensor cleaning
Buffer clearing time	27 seconds with Kingston 100x CF card, after 9 RAW-mode shots 6.1 seconds, after 9 large/fine JPEG shots of a worst-case noise target Up to 22 seconds after 24 large/fine JPEG shots of lower-density noise target	Worst case buffer clearing time. -- This is the delay after a set of shots before you can remove the card. Some cameras won't retract their lenses and shut down until the buffer is cleared. (Buffer depth and clearing time depend heavily on subject complexity and detail.)
Mode switching
Play to Record, first shot	0.2 seconds	Time until first shot is captured
Record to play	2.0 seconds	Time to display a large/fine file immediately after capture
Display recorded image	0.4 second	Time to display a large/fine file already on the memory card.
Shutter response (Lag Time):
Full Autofocus	0.20 second	Time from fully pressing shutter button to image capture, zoom lens at wide angle position.
Prefocused	0.105 second	Time to capture, after half-pressing and holding shutter button.
Continuous AF	0.12 second	This mode usually shows no speed increase with our static subject; we have no way to measure performance with moving subjects
Manual focus	0.13 second	For most cameras, shutter lag is less in manual focus than autofocus, but usually not as fast as when the camera is "prefocused"
Cycle time (shot to shot)
Single Shot mode Large Fine JPEG	0.35 seconds; 9 frames total; 6.1 seconds to clear*	Time per shot, averaged over 9 shots. Buffer depth depends greatly on subject complexity & detail. Worst case noise target (poor compressibility) gives 9 frame buffer depth and 6-second clearing times*, lower-density subjects give 24 frames, with 22 second clearing time.
Single Shot mode 640x480 JPEG	0.35 seconds; 3 seconds to clear*	Time per shot, averaged over 20 shots. (Essentially unlimited buffer capacity with a fast memory card*, irrespective of subject complexity.)
Single Shot mode RAW	0.36 seconds; 9 frames total; 27 seconds to clear*	Time per shot, averaged over buffer capacity. High-density noise target gives buffer depth of 9 frames, with clearing time of 27 seconds. Low density noise target gives buffer depth of 11 frames, 23 seconds clearing time.
Early shutter penalty?	No	Some cameras refuse to snap another shot if you release and press the shutter too quickly in Single Shot mode, making "No" the preferred answer
Continuous mode Large Fine JPEG	0.33 second (3.00 frames per second); 8 frames total; 21 seconds to clear*	Time per shot, averaged over buffer length of 8 shots with worst-case noise target. Less complex subjects give buffer depths of up to 22 frames, buffer-clearing time increases only slightly.
Continuous mode 640x480 JPEG	0.33 second (3.00 frames per second); 3 seconds to clear* (with moderately complex subject)	Time per shot, averaged over 20 shots, buffer depth more or less unlimited. (60+ shots with worst-case noise target, no limit with less-complex subject. Buffer clearing as long as 23 seconds* with complex target, less)
Continuous mode RAW	0.33 second (3.00 frames per second); 8 frames total; 27 seconds to clear*	Time per shot, averaged over buffer length of 8 frames with worst-case noise target. Less-complex subjects can result in buffer depths of 9-10 frames.
Flash recycling	3 seconds	Flash at maximum output
Download speed
Windows Computer, USB 2.0	1165 KBytes/sec*	Typical Values: Less than 600=USB 1.1; 600-770=USB 2.0 Low; 771-4000=USB 2.0 High
*Note: Buffer clearing times measured with a Kingston Ultimate 100x CF memory card. Slower cards will produce correspondingly slower clearing times. Slow cards may also limit length of bursts in continuous mode, and reduce transfer rates when downloading to a computer.

The Canon EOS Digital Rebel XTi's performance is quite fast, beginning with a quick start-up time of only 0.4 second. The sensor cleaning potentially adds an additional 2.1 seconds to the startup time, but you can override the cleaning cycle at any time by pressing the shutter button. (On shutdown, you can remove the memory card without waiting for the sensor cleaning cycle to complete.)

Shutter lag is quite good in standard autofocus mode, and though "prefocus" times (half-pressing and holding down the shutter button before the final exposure) are fast at 0.105 second, we've seen slightly faster results from competing cameras. Shot-to-shot cycle times are quite zippy, at about 0.35 seconds for large/fine JPEGs in single-shot, and the camera has ample buffer depth. As noted in the table above though, buffer depth varies radically depending on the complexity of the subject. Very complex subjects with lots of fine detail don't JPEG-compress as well, so fewer of them fit into the buffer. A worst-case noise target shot at ISO 1,600 results in a buffer depth of 9 frames, while the camera can capture up to 24 shots of a more typical subject without pausing. In RAW mode, buffer capacity isn't as strong a function of subject complexity, but there's still some effect, with buffer depth ranging from 9 to 11.

Continuous-mode speed is fairly quick as well, at three frames/second, for anywhere from 8 to 24 shots in succession (the speed doesn't depend on resolution or compression, but the series length will vary with those parameters). The flash is fast as well, taking only three seconds to recharge after a full-power shot. Download speeds are also speedy, so you won't feel the need for a separate card reader. Bottom line, the Rebel XTi is very responsive and quick on the draw, fast enough to capture fast-paced action from sports to wildlife. The XTi is also perfectly suited for photographing busy children, and its fast shutter response means you won't miss a shot while waiting for the autofocus. Overall, very good results.

Battery and Storage Capacity

Battery
Good battery life with included battery pack, though a backup is always recommended.

Operating Mode	Number of Shots
50% flash use	370
No flash use	500

The Canon EOS Digital Rebel XTi uses a custom rechargeable LiIon battery for power, and comes with both a single battery and charger. Though runtime is quite good, we do recommend picking up a spare battery and keeping it freshly charged and on-hand.

The table above shows the number of shots the camera is capable of (on a fully-charged rechargeable battery), based on CIPA battery-life and/or manufacturer standard test conditions.

(Interested readers can find an English translation of the CIPA DC-002 standards document here. (180K PDF document))

Storage
The Rebel XTi accepts CompactFlash memory cards, though no card is included with the camera.

Image Capacity vs Resolution/Quality 1 GB Memory Card		Fine	Normal	RAW
3,888 x 2,592	Images (Avg size)	208 4.9 MB	411 2.5 MB	94 10.8 MB
3,888 x 2,592	Approx. Compression	6:1	12:1	1.4:1
2,816 x 1,880	Images (Avg size)	359 2.8 MB	728 1.4 MB	-
2,816 x 1,880	Approx. Compression	6:1	12:1	-
1936 x 1288	Images (Avg size)	652 1.5 MB	1,305 0.8 MB	-
1936 x 1288	Approx. Compression	5:1	10:1	-

We strongly recommend buying a large capacity CompactFlash memory card. at least a 512MB card, preferably a 1GB one, to give yourself extra space for extended outings. (Check the shopping link above, cards are really cheap these days, so no reason to skimp.)