The Nikon D3200's 24.2MP image resolution makes the Nikon D5100's 16.2MP look a bit of a poor relation, and the D3200 also equals the D5100's speedy continuous frame rate of 4fps. The D3200's EXPEED image-processing engine is also a generation newer, and it's much faster at clearing raw files through the buffer and into the waiting memory card.
The Nikon D5100 still has plenty to shout about, though, with a number of wide-ranging Custom Functions.
For example, you can choose release-priority or focus-priority when using continuous autofocus. The former will keep firing regardless of autofocus tracking after the first shot, whereas the latter will only take subsequent images if focus-tracking remains locked onto the target.
There's also an exposure delay mode that is particularly useful for avoiding mirror-bounce when a camera and long telephoto lens are mounted on a tripod. It's similarly useful for macro photography, though this is beyond the sports remit. These and many other custom settings are lacking on the Nikon D3100 and Nikon D3200.
Like the other two Nikon cameras in the group, the D5100 has no fewer than four continuous autofocus modes. These are single-point AF, Dynamic-area AF, Auto-area AF and 3D tracking. This gives great flexibility when choosing the ideal mode for shooting a wide range of sports scenarios. And, as with the Canon EOS 600D, you get the joy of a fully articulated LCD screen.
Apart from being a bit sluggish at clearing its internal buffer to a memory card (a complaint we've also levelled at the Nikon D7000), the Nikon D5100's performance is excellent.
Autofocus and metering are accurate and it simply delivers wonderfully vibrant sports images practically every time, even in challenging lighting conditions.
A lot of this is due to the Active D-Lighting system that's also employed on the Nikon D3100 and Nikon D3200. However, as with most other settings, it's more customisable on the Nikon D5100, giving greater control.
With classic Nikon image attributes, outdoor shots from the D5100 are a little darker, but full of vibrancy and rich colour saturation.
The D5100 delivers better image resolution than the 18MP 600D, despite its modest 16.2MP sensor, putting it in second place here.
A good compromise between the D3100 and D3200, high ISO shots look nice and smooth, but with good retention of fine detail.
Slightly darker exposures make for very bold colour rendition, but accuracy is very good and much better than with the D3100.
Image test verdict
Rich, vibrant and well-saturated shots are hallmarks of the D5100, and it also fares very well in low lighting conditions at high ISO settings.