The SD400 is externally almost identical to the 4MP SD300, and features the same easy to use - and well designed - control layout. The body is almost entirely free of protrusions, and the smooth, cool all-metal body exudes class, while the quality of construction is exemplary. Despite the lilliputian dimensions, the SD400 is far from lightweight; at around 150g (4.7 oz) fully loaded it has enough weight to feel remarkably stable in the hand. The rear of the camera is dominated by the 2.0-inch LCD screen, while the majority of the controls are clustered around a circular four-way controller. This is a true point and shoot camera, and the majority of features most users will want to regularly access - flash mode, macro/infinity focus, flash mode, metering pattern, drive mode and self timer - all get their own external buttons. Everything else - white balance, image size/quality, ISO etc - are accessed via the tried and tested 'FUNC' menu.

In your hand

It may be small enough to hide behind a credit card, but the SD400 handles remarkably well as a picture-taking tool. The minimalist squared-off design and rounded edges make it a pleasure to hold, and the weight gives it some stability - a tiny raised area on the rear acts as a thumb 'grip', and single-handed operation is perfectly possible (though something this sleek, smooth and fairly weighty camera feels a lot safer held with both hands). I was surprised that camera shake wasn't as much of a problem as I'd anticipated, a result of the solid build and a design that doesn't place the shutter release right on the end of the camera.

Body elements

The combined battery and SD card slot sits under a slightly flimsy hinged door on the base of the camera (the door is one of the few bits of plastic on the entire thing). The 3.7v, 760mAh Li-ion battery pack will only give you around 150 shots if you use the LCD (CIPA standard), but if you switch to the optical viewfinder and only use the LCD to check your pictures every now and then you can easily get almost 400 shots out of a single charge.

The included battery charger takes around 90 minutes to recharge a fully depleted battery. I would certainly recommend investing in a second battery if you like to use the LCD a lot (and why wouldn't you?).

An optional mains adaptor for the camera takes the place of the battery, with the mains cable threaded through a hole under a flap on the battery compartment door.

On the right end of the body (looking from the back) you find the only other piece of plastic on the SD300's exterior. This fake chrome 'flap' is on a plastic hinge and covers the AV (audio and video) out and USB connectors.
The 2.0-inch screen is bright and fairly sharp (though I have to say that 118,000 pixels on a two-inch screen really isn't enough for a really crisp image). The anti-reflective coating helps outdoor use (as does the automatic brightening in bright conditions), but it's still hard to see in direct sunlight. The monitor automatically 'gains up' in low light, and remains perfectly usable in very dim conditions.
The optical viewfinder is nothing to write home about; small, not that clear, has no dioptre adjustment and only shows about 82% of the scene. That said, it's no worse than 99% of its competitors. If you do decide to use the optical viewfinder you can, however, extend the battery life to almost 400 shots on a single charge - and reduce shutter lag. Two LEDs to the right of the viewfinder indicate focus and flash status.
The small built-in flash is a little under-powered, but perfectly usable in most social situations. There are five flash modes available; auto, auto with red-eye reduction, on (forced), off and slow-synchro. The stated range of the flash is 1.6 to 11.5ft (0.5 - 3.5m) at the wide end of the zoom and 1.6 to 6.6ft (0.5 - 2.0m) at the long end (auto ISO). You can also use the flash in macro mode in the 30cm to 50cm range (1.0 to 1.6 ft).
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 around 30 feet.
The 3x optical zoom covers a useful range equivalent to 35-105mm, with a maximum aperture that varies from a nice bright F2.8 at the wide end to a less impressive F4.9 at the long end. The zoom retracts completely flush into the body when powered down. In normal shooting mode you can focus down to 30cm, the macro mode gets you down to a very close 3cm at the wide end of the zoom.
The large shutter release sits on top of the camera, centered around an inch in from the edge. 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 - there only appear to be six steps from wide to tele, making fine framing a little awkward. Next to the shutter release, you will find the main power switch.
The main mode switch sits directly below the shutter release on the rear of the camera. There are three positions; play, movie mode and stills mode. You can power the camera up in play mode and the lens will not extend until you move to record mode.
The inclusion of such a large monitor has meant the main controls have been moved to a cluster on the right side of the camera's rear. Canon has avoided the temptation to remove external controls and relegate commonly accessed features to menus.