"Picky Details" for the Canon PowerShot SD20 digital camera
(Timing, Power, and Storage Info)
Timing
When you press the shutter release on a camera, there's usually a lag time or delay before the shutter actually fires. This corresponds to the time required for the autofocus and autoexposure mechanisms time to do their work, and can amount to a fairly long delay in some situations. Since this number is rarely reported on (and even more rarely reported accurately), and can significantly affect the picture taking experience, I routinely measure both shutter delay and shot to shot cycle times for all cameras I test, using a test system I designed and built for the purpose. (Crystal-controlled, with a resolution of 0.001 second.) Here are the numbers I collected for the Canon PowerShot SD20:
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(secs) |
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| Power On -> First shot |
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LCD turns on and lens extends forward. Fairly fast. |
| Shutdown |
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First time is time to retract lens, second time is worst-case buffer-clearing time. First time is fairly fast, second is a little long, but corresponds to clearing 8 large/fine shots from the buffer memory, so isn't too bad. |
| Play to Record, first shot |
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Time until first shot is captured. About average. |
| Record to play |
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First time is that required to display a large/fine file immediately after capture, second time is that needed to display a large/fine file that has already been processed and stored on the memory card. A little on the slow side, these days. |
| Shutter lag, full autofocus |
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Right about average. (Which is still slower than most users would like.) |
| Shutter lag, prefocus |
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Time to capture, after half-pressing shutter button. Very fast. |
| Cycle Time, max/min resolution |
2.82 |
Shoots at the same rate for large/fine images or "TV" mode (640x480) images. Times are averages. In large/fine mode, takes 8 shots, then slows to 4.3 seconds per shot. In TV mode, maintains this rate for over 100 shots. Buffer clears in 16 for large/fine mode, 5 second for TV mode. On the slow side, the SD20 wouldn't be your first choice for action shooting. |
| Cycle Time, continuous mode, max/min resolution | 1.16 / 1.13 (0.86 / 0.88fps) |
First number is for large/fine files, second number is time for "TV" size images. Times are averages. In large/fine mode, takes 8 shots, then slows to 2.5 seconds per shot. In TV mode, maintains this rate for over 100 shots. Buffer clears in 16 for large/fine mode, 17 second for TV mode. On the slow side, but fairly typical for a subcompact digital camera. |
Average shutter lag, slightly slower than average cycle times. With a full-autofocus shutter lag of 0.78 second, the Canon SD20 comes in on the fast side of average in that category. It's slower from shot to shot though (not uncommon among subcompact digicams), at 2.82 seconds per shot regardless of the resolution setting. In continuous mode it's still not terribly fast, at 1.16 seconds per large/fine shot. (Although it can capture 8 shots that quickly, before having to wait for the memory card to catch up.) Overall probably not a first choice for fast-paced action shooting.
Power
Decent battery life for a subcompact digital camera. The Canon PowerShot SD20 uses a custom rechargeable LiIon battery for power. It doesn't have an external power jack that we could plug into, so we couldn't perform our usual exacting power-drain measurements. We did find that a freshly charged battery would run the camera in its worst power-drain mode (capture mode with the LCD running) for 87 minutes though. - Not bad for a subcompact digital camera, but I'd still advise purchasing a second battery along with the camera, if you plan any even slightly extended outings with it.
Storage Capacity
The Canon PowerShot SD20 stores its photos on SD/MMC memory cards, and a 32 MB card is included with the camera. (I strongly recommend buying at least
a 64 MB card, preferably a 128 MB one, to give yourself extra space for extended
outings.) The chart below shows how many images can be stored on the included
32 MB card at each size/quality setting.
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Resolution/Quality 32 MB Memory Card |
Fine | Normal |
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| 2592 x 1944 | Images (Avg size) |
12 2.6 MB |
21 1.5 MB |
43 737 KB |
| Approx. Compression |
6:1 | 10:1 | 20:1 | |
| 2048 x 1536 | Images (Avg size) |
19 1.7 MB |
34 934 KB |
67 475 KB |
| Approx. Compression |
6:1 | 10:1 | 20:1 | |
| 1600 x 1200 | Images (Avg size) |
30 1.0 MB |
54 589 KB |
102 311 KB |
| Approx. Compression |
6:1 | 10:1 | 19:1 | |
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Images (Avg size) |
115 278 KB |
177 180 KB |
115 KB |
| Approx. Compression |
3:1 | 5:1 |
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Download Speed
The Canon PowerShot SD20 connects to a host computer via a USB interface. Downloading files to my Sony desktop running Windows XP (Pentium IV, 2.4 GHz), I clocked it at 504 KBytes/second, a reasonably fast rate. (Cameras with slow USB interfaces run as low as 300 KB/s, cameras with fast v1.1 interfaces run as high as 600 KB/s. Cameras with USB v2.0 interfaces run as fast as several megabytes/second.)
SD20 Test Images
SD20 Specifications
SD20 "Picky Details"
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