Canon PowerShot A640 Review
Timing & Performance
At one time Canon's A series compacts were considerbly less responsive in virtually every area than their more glamorous Ixus/Elph/S/G cousins, mainly because they were still using the older DIGIC processor when the rest of the lineup had moved to DIGIC II. That all ended with the A610/620, which saw the introduction of the DIGIC II processor to the A series, and with it a huge performance boost. The good news is that the A640 offers pretty much the same performance as the A620 before it (aside from a slightly slower burst mode and slightly slower playback thanks to the larger files). Surprisingly it also offers performance that is broadly comparable with the DIGIC III-equipped G7 and in most areas it is up with the best cameras in its class. Our only complaints are the occaisional focus hunting (particularly at the long end of the zoom and in macro mode) and the rather sluggish flash performance once the batteries start to run down.
All times calculated as an average of three operations. Unless otherwise stated all timings were made on a 3648 x 2736 Super-Fine JPEG image (approx. 4,300 KB per image). The media used for these tests was a 1.0GB SanDisk Extreme III SD card.
Power: Off to Record
|Power: Off to Play||Image displayed||1.9|
|Power: Record to Off||Lens retracted and all activity ceased||1.7|
|Power: Play to Off||When buffer is empty (lens extended)||1.4|
|Power: Play to Off||When buffer is empty (lens already retracted)||< 0.2|
|Record Review||Image displayed||~ 0.5|
|Mode: Record to Play||1.6|
|Mode: Play to Record||~ 1.1|
|Play: Magnify||To full magnification (10x)||0.8|
|Play: Image to Image||Time to display each saved image||~ 0.35|
|Play: Thumbnail view||3 x 3 thumbnails||0.5|
|Zoom from Wide to Tele||35 to 140 mm (4 x)||1.5|
|Half-press Lag (0->S1)||Wide angle (AiAF or FlexiZone focus)||~ 0.4 *1|
|Half-press Lag (0->S1)||Telephoto (AiAF or FlexiZone focus)||~ 0.5 *2|
|Half to Full-press Lag (S1->S2)||LCD live view||~ 0.08|
|Half to Full-press Lag (S1->S2)||Optical Viewfinder||~ 0.05|
|Full-press Lag (0->S2)||LCD live view, wide angle||~ 0.6|
|Off to Shot Taken||LCD live view||1.7|
|Shot to Shot||Flash off||1.7|
|Shot to Shot||Flash on (red-eye reduction off) *4||2.6|
|Shot to Shot||Flash on (red-eye reduction on) *4||3.2|
|*1||Focus speed varies according to shooting conditions; at the wide end in good light it is usually 0.3 - 0.4 second, but in low contrast / low light and macro shots this can extend to about 0.5 or 0.6|
|*2||Again this figure will be higher in low light / low contrast situations - to as long as 1.1 seconds in the worst cases.|
|*3||Depends on focus speed; this is the average.|
|*4||In this test the subject distance is only 3 feet (0.9 m) - the recycle time will increase at greater subject distances.|
Lag Timing Definitions
|Half-press Lag (0->S1)
Many digital camera users prime the AF and AE systems on their camera by half-pressing the shutter release. This is the amount of time between a half-press of the shutter release and the camera indicating an auto focus & auto exposure lock on the LCD monitor / viewfinder (ready to shoot).
|Half to Full-press Lag (S1->S2)
The amount of time it takes from a full depression of the shutter release button (assuming you have already primed the camera with a half-press) to the image being taken.
(Take shot, AF/AE primed)
|Full-press Lag (0->S2)
The amount of time it takes from a full depression of the shutter release button (without performing a half-press of the shutter release beforehand) to the image being taken. This is more representative of the use of the camera in a spur of the moment 'point and shoot' situation.
(Take shot, AF/AE not primed)
The tables below show the results of our continuous shooting test, indicating the actual frame rate along with maximum number of frames and how long you would have to wait after taking the maximum number of frames before you could take another shot. Media used for these tests was a 1.0GB SanDisk Extreme III SD card. Shutter speed was kept above 1/200 sec during these tests.
Continuous drive mode
The A640 has a single continuous shooting mode, which in our tests averaged around 1.5 fps, which is hardy class-leading, but perfectly adequate for most users. In continuous shooting mode the A640 does not show a live preview, but does display a brief review image for each picture taken. With a fast card it appears to be impossible to fill the buffer, so you can keep shooting until you run out of card space.
Frames in a burst *1
|3648 x 2736 JPEG Super-Fine||Continuous||1.5 fps||No limit||n/a|
|3648 x 2736 JPEG Fine||Continuous||1.5 fps||No limit||n/a|
|3648 x 2736 JPEG Normal||Continuous||1.5 fps||No limit||n/a|
|2816 x 2112 JPEG Super-Fine||Continuous||1.4 fps||No limit||n/a|
|2272 x 1704 JPEG Super-Fine||Continuous||1.4 fps||No limit||n/a|
|*1||In a single "burst" (finger held down on shutter release).|
|*2||With the shutter release held down. With a fast card it is impossible to fill the buffer|
|*3||Average speed - it will slow down if the camera has trouble focusing|
File Write / Display and Sizes
Timings shown below are the time taken for the camera to process and "flush" the image out to the storage card, the timer was started as soon as the shutter release was pressed and stopped when activity indicator went out. This means the timings also include the camera's processing time and as such are more representative of the actual time to "complete the task". The media used for these tests was a 1.0GB SanDisk Extreme III SD card.
Time to store
File size *1
Images on a *2
|3648 x 2736 JPEG Super-Fine||~1.3||~0.35||4,480 KB||239|
|3648 x 2736 JPEG Fine||~1.1||~0.35||2,830 KB||399|
|3648 x 2736 JPEG Normal||~0.8||~0.2||1,175 KB||825|
|2816 x 2112 JPEG Super-Fine||~1.1||~0.25||2,700 KB||361|
|2272 x 1704 JPEG Super-Fine||~0.9||~0.2||1,900 KB||487|
|*1||All file sizes are an average of three files. As is the case with JPEG it's difficult to predict the size of an image because it will vary a fair amount depending on the content of the image (detail and noise).|
|*3||With transition effects turned off|
It's not the fastest write speed in the world, but the A640's generous and seemingly fast buffering means it's pretty irrelevant. A faster card will certainly benefit you if you like to shoot lots of shots in rapid succession or use the movie mode, but it's not going to make a significant difference for casual snaps.
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