The D3100 has a little pop-up flash with a guide no. of 12m at ISO 100 - pretty well standard for this class of camera.

The performance is certainly impressive, given this relatively modest power. The skintones are well rendered and the exposure is well-judged.

Highlight clipping / recovery

The D3100 has a similar tendency to the D7000 we reviewed recently, in that its matrix metering can give over-bright exposures when the scene in front of it contains a lot of shadow regions, most obviously in bright, contrasty conditions. This can result in the clipping of highlight detail, which is completely unrecoverable in JPEG but can be partially fixed if you shoot raw. Like most SLRs there's not a huge amount of additional highlight range to play with in raw, though, and the more you try to recover the worse the colour accuracy is likely to be (as the individual colour channels clip successively in the raw file). At the most you can hope to recover about a stop of luminance information.

The example below shows this in practice. The camera's preferred exposure is significantly too bright, with the matrix metering obviously biasing towards the lower half of the frame and failing to protect the highlights. Applying negative exposure compensation to the raw file brings back some of the lost detail, but it's clear that the extreme highlights have been completely lost, and there's little colour information in the over-exposed regions of the sky. A duplicate shot, with negative exposure compensation applied, shows this clearly - retaining detail in the stonework of the background building, and holding the correct hue throughout the sky, while (crucially) not blocking up the shadows in any way.

JPEG: Metered Exposure (1/40 sec F11 ISO 100)
RAW: Metered Exposure, -1 EV correction in development (ACR)
JPEG: -2/3 EV exposure compensation (1/80sec F11 ISO 100)

The same is true if you apply negative exposure compensation when developing an over-exposed raw in-camera; regions which are clipped in the JPEGs will be recovered to an extent, but with no guarantee of colour accuracy. Most obviously in the example below, a decent amount of sky detail has been recovered, but the most strongly overexposed regions have simply been painted grey in the re-developed image.

JPEG: Metered Exposure (1/40 sec F11 ISO 100)
RAW: Metered Exposure, -1 EV correction using in-camera raw conversion

Shadow Noise

Recently we've reviewed a couple of cameras (namely the Nikon D7000 and Pentax K-5) which use a new generation of sensor that shows exceptionally low shadow noise at base ISO. The D3100 also has a new sensor, but it doesn't share the same characteristic. In the example below we've taken our studio comparisons at ISO 100 and developed them in Adobe Camera Raw with 3 stops of exposure compensation to pull up the shadows. The D3100 shows visibly more noise than the D7000 in the crops.

To be fair, though, this isn't in any way a negative point against the D3100 - we wouldn't expect any current camera in its price range to do any better in this respect.

Nikon D3100 - ISO 100 raw, ACR +3.0EV Nikon D7000 - ISO 100 raw, ACR +3.0EV
100% crop 100% crop
100% crop 100% crop

Overall Image Quality / Specifics

In general the D3100 delivers excellent images, as you'd expect from one of the most mature DSLR lines on the market. Typically for a consumer-level Nikon it delivers punchy, saturated colour, with white balance that tends towards the warm side: overall a pretty crowd-pleasing performance. Like many other recent APS-C SLRS its high ISO image quality is very impressive too, delivering results which are excellent at up to ISO 800 at least, and perfectly useable for most purposes even at ISO 3200. The default JPEG sharpening is distinctly conservative, producing considerable less-detailed output than its peers. You can increase the setting in camera but the best results come from shooting raw files and applying higher levels of sharpening when you process them. So on the whole, when it gets things right, there's very little to complain about.

As discussed above, though, if the D3100 has one obvious flaw it would a distinct tendency towards overexposure in bright, contrasty conditions, when its matrix metering is arguably too happy to expose for the shadows and allow the highlights to blow. This is the case even when Active D-Lighting is turned on, which is disappointing as these are precisely the kind of high dynamic range images ADL is supposed to be most effective for, allowing the camera to lift the shadows in software while protecting the highlights.