Canon PowerShot A640 lens

The Canon PowerShot A640 is equipped with a 4x optical zoom which delivers an equivalent range of 35-140mm; the actual specification is 7.3-29.2mm f2.8-4.1. This lens, which is exactly the same as that on the earlier A620, has the edge over typical 3x ranges of rival compacts, being able to zoom-in that bit closer.

Like most compacts the actual zoom lurches slightly from one focal length to the next – we counted nine discrete steps, although annoyingly there’s no numbers to accompany them on-screen until you reach the boundary between optical and digital zoom.

Canon PowerShot A640		Fujifilm FinePix F30		Sony Cybershot DSC N2
7.3-29.2mm at 7.3mm (35mm equivalent)		8-24mm at 8mm (36mm equivalent)		7.9-23.7mm at 7.9mm (38mm equivalent)

To illustrate the coverage in practice we mounted the A640 on a tripod and took photos with the lens zoomed all the way out, then all the way in. We then repeated the process moments later for the Fujifilm FinePix F30 and Sony Cyber-shot DSC N2 for comparison. The shots above were taken at each camera’s widest position.

Canon PowerShot A640		Fujifilm FinePix F30		Sony Cybershot DSC N2
7.3-29.2mm at 29.2mm (140mm equivalent)		8-24mm at 24mm (108mm equivalent)		7.9-23.7mm at 23.7mm (114mm equivalent)

The images above are from each camera zoomed-in to their longest focal lengths and the Canon A640’s 140mm equivalent shows a slight edge over its rivals. It’s handy for getting in a little tighter, although if you’re after a more significant difference from a PowerShot as standard you’ll need to go for the 6x optical range of the A710 IS, or the 12x range of the super-zoom S3 IS; both of these models also boast Image Stabilisation to combat camera shake whereas the A640 does not.

The A640 does however support the optional WC-DC58N wide angle and TC-DC58N tele-converter lens attachments which multiply the focal length by 0.7x and 1.75x respectively. To attach these you first press the button to the lower right of the lens to release the housing surrounding it. You must then fit the optional LA-DC58F conversion lens adapter onto which either a filter or the converter lenses can be mounted.

The PowerShot A640 also boasts excellent macro facilities and can focus as close as 1cm when zoomed-out to wide angle. This gives the A640 amazing close-up opportunities, although beware at this sort of distance it’s difficult not to cast a shadow on the subject. See our Results and Gallery pages for examples.

Viewfinder

In a market where an increasing number of new compacts only offer composition using their main colour screens, the A640 is unusual in that it also provides an optical viewfinder. These may seem old-fashioned compared to using a nice, big colour screen, but there are benefits.

The main one is having an alternative means of composition when the colour screen becomes hard to view, such as under direct sunlight. Since you’re not using any power to illuminate a colour screen when composing with the optical viewfinder, you’ll also extend your battery life – indeed Canon claims up to three times as many shots can be taken with the viewfinder alone compared to using the screen.

Of course it’s highly unlikely you’d use the viewfinder exclusively for composition and unlike the screen it won’t show 100% coverage, exposure information nor focus indication beyond a light, but it’s still good to have it as an option. If your battery's running too low to run the screen for much longer, it could mean the difference of missing a crucial shot or grabbing it.