Although it bears an strong family resemblance to the A610/620 models that preceded it, the A640 is - to my eyes - a much better looking camera, thanks to its black livery and chrome accents. As mentioned earlier, it's slightly wider (though only about 5mm) and - thanks to the larger screen - the main rear controls have been squashed a little, but thankfully the size of the camera (it's not small by any definition) this hasn't hampered handling.

As with its predecessors the A640 is superbly constructed with a lot of metal (the sides and part of the back are high impact plastic) and a a fantastic fit and finish. The A series may well have started life as a budget alternative to the S and G cameras, but there is nothing 'cheap' about them these days (in reality they're not even that inexpensive any more) - using the A640 side by side with the G7 on a recent trip I was struck by how they both have the same high quality, solid feel. What you don't get with the A640 is the plethora of external controls you'll find on cameras like the G7; there's no ISO button, and the lack of a shortcut button means you have to use the FUNC menu to change white balance and so on. There is, however, a Custom setting on the mode dial, so you can at least save one set of preferences.

Side by side

For comparison here's the A640 (center) between the G7 on the left and the A710 IS on the right. Weight-wise it sits roughly between the two, and it's roughly the same size as the G7 (though it is a completely different shape) and a little larger than the A710 IS.

In your hand

First impressions of the A640, like the A620 and A95 before it, are that this is a very solid camera indeed. The front and top are encased in lightweight metal, the rear and grip are plastic. Handling is superb - far better than the G7, thanks to the sizeable grip and - once you've loaded up a set of AA batteries - it is very well balanced and heavy enough to feel very, very stable in the hand. The trend for smaller and smaller cameras (fueled in no small part, it should be said, by the success of Canon's own Elph/Ixus range) has seen ergonomic concerns fly out of the window in favor of style statements. The A640 is a perfect example of how taking the opposite approach might not produce the prettiest camera in the world, but it makes a huge difference to its usefulness as a serious photographic tool.

Body elements

As with all A series PowerShots, the A640 is powered by AA batteries (four). Rechargeable (NiMH) batteries are not supplied in the box, so you'll need to budget for at least one set. The good news is that battery life is superb - Canon quotes 500 shots (using the CIPA standard, LCD monitor on) from a fully charged set of NiMH cells, and up to 1500 shots if you turn the LCD off and use the viewfinder. Our experience bore this out. Impressive.
The card slot sits under a fairly sturdy hinged door at the base of the grip. Like other A series cameras the SD slot is in the same compartment as the batteries, meaning you need to be a bit careful when swapping cards that the batteries don't fall out. It also, annoyingly, means that you can't change cards when the camera is mounted on a tripod. In a change from the A620 you can now use higher capacity SDHC cards.

Despite being bigger, the LCD still only has 115,000 pixels, which is kind of stretching things for a 2.5" screen. It's not super-bright either (though the refresh rate is very high), meaning it can be difficult to see in direct sunlight. It's about 15% dimmer than the G7's screen, which also has better anti-reflective coating (click here for a side by side shot), and in use you can really, really see the difference.

Still, it's perfectly usable 99% of the time, and is the only real example of cost-cutting on the whole camera.

The screen uses Canon's familiar 'vari-angle' design to allow it to be tilted to virtually any angle, and to be stored 'face in' to the camera body when not in use. As someone who likes to shoot from odd low or high angles I'm a huge fan of vari-angle screens, and this is one area at least where the A640 trumps the G7.

The optical viewfinder is nothing to write home about; small with no dioptre adjustment and only showing around 80 per cent of the frame.That said it is fairly bright and clear. If you do decide to use the optical viewfinder you can, however, extend the battery life to almost 1500 shots on a single set of NiMH cells - and reduce shutter lag. Two LEDs to the right of the viewfinder indicate focus and flash status.
The small built-in flash appears to be identical to the A620. There are three flash modes available; auto, on (forced), and off. You can turn red eye reduction and slow synch (including options for 1st or 2nd curtain synch) on or off using the on-screen menus. Canon sells an add-on slave flash unit (the HF-DC1), which attaches to the camera via a bracket and extends the flash range to 30 feet.
Again, the lens appears to be identical, covering a useful 35-140mm (4x optical) range. As with previous A series cameras the cosmetic ring around the base of the lens can be removed to allow the attachment of wide or tele converters.
The large shutter release sits on top of the grip. It has a nice positive feeling and a distinct 'half way' point, meaning you won't accidentally take a shot when trying to activate the AF. The zoom lever is a large circular 'collar' around the shutter release. The zoom action is a bit on the 'jumpy' side, which can make fine framing a little awkward (there are only 7 steps over the entire 35-140mm range).
On top of the camera, behind the shutter release, sit the main power (on/off) switch, activity light and mode dial. This is pretty standard Canon stuff - idiot-proof Auto mode, manual and semi automatic exposure modes, movies, stitch assist and scene modes, plus a handy Custom mode (you create your own settings - including stuff like ISO and white balance).
The four-way controller is used to navigate the on-screen menus. In record mode the up key also changes flash mode, and the down key toggles auto, macro and manual focus modes. The middle button activates Canon's ubiquitous FUNC menu.
The USB and AV ports - plus a socket for the optional mains adaptor - sit under a flexible plastic cover on the side of the grip.