Dynamic Range

The dynamic range of a camera's sensor typically comes into play when photographing scenes in harsh, contrasty light. Depending on your definition of the term, you can measure it in a number of ways - and there are websites that do a great job of this. It would have been rather pointless to try and come up with our own set of figures - instead, we're showing you how each camera fared when tasked with capturing a typical, real-world high-contrast scene with radiant white buildings bathing in the summer sun and dark tree trunks hiding in deep shade.

Note that at full resolution, the two cameras take pictures with different aspect ratios. In order to make this comparison easier, we cropped both shots to show approximately the same field of view.

Much to our surprise, both cameras handled this difficult scene well, with absolutely no clipped highlights or blocked shadows.

The crops below show how well each camera retained detail and tonality in the highlights - an excellent performance given that the glaring white building was almost blinding to the naked eye.

Olympus OM-D EM-5	Nikon D7000

The deepest shadows are extremely dark in both pictures but...

Olympus OM-D EM-5	Nikon D7000

...even these dark patches contain loads of tonal and colour information, as seen in the brightened crops below.

Olympus OM-D EM-5	Nikon D7000

Here you can see a marked difference between the two cameras, with the D7000 crop being noticeably cleaner and smoother even after such a heavy dose of image manipulation - this is where the benefits of having larger sensor photosites and 14-bit raw files become evident.

In short both cameras deliver an excellent dynamic range at base ISO but if, for whatever reason, you need to dig really deep into the shadows you'll find that the Nikon D7000 will give you better results.

Highlight Headroom - Raw vs. JPEG

We were also curious if shooting raw offered any advantage over JPEGs in terms of highlight retention. To find out, we shot the same backlit scene with both cameras set to JPEG+raw capture.

This is what the out-of-camera JPEG from the D7000 looked like (again we cropped the images below to show approximately the same field of view for easier comparison).

As you can see the subject is well exposed but large parts of the sky are blown. The JPEG from the Olympus OM-D E-M5 was similar, with a properly exposed building and minimal detail retention in the sky.

Next, we took the D7000 raw file and applied a bit more than -1EV of exposure compensation along with some Curves adjustment to prevent the midtones from coming out overly dark. The result is shown below.

As you can see all the seemingly lost sky detail was recovered, with the image showing rich tonal gradations everywhere.

Applying a similar degree of EC and Curves adjustment to the Olympus OM-D E-M5 raw file - taken just a few minutes before the Nikon shot - has yielded similar results: all the highlight blow-out seen in the out-of-camera JPEG is gone, with the sky showing  great tonality throughout.

This means that in addition to offering a respectable dynamic range (even in the JPEGs), both cameras have more than a full stop of extra highlight headroom in the raw files, at least at base ISO - which is good to know as it means shooting raw can often save an image that may look partly overexposed when played back in-camera.

Conclusion

Both the Nikon D7000 and the Olympus OM-D E-M5 are highly capable cameras that can handle most photographic situations with ease. The smaller, lighter and quieter E-M5 is better suited to travel and street photography and any other genres/tasks where a discreet and lightweight camera is preferred. However, if you have average to large hands or simply long fingers, and do not mind hauling around a larger and heavier kit, you are likely to find the more ergonomically designed D7000 easier and more pleasurable to use in the long run. Otherwise both cameras are rugged, highly configurable and well designed tools that can produce high-quality results in a variety of circumstances.

Although I'm a big fan of traditional SLRs and their through-the-lens optical viewfinders, I did prefer the E-M5's EVF for its ability to “gain up” in low light, show a magnified view of the subject for accurate manual focusing and display various shooting info including a live histogram. Perhaps the biggest surprise was the auto focus performance - the Olympus OM-D E-M5 has a stunningly mature and lightning-fast AF system that works very well even when using an off-centre focus point in low light, something the Nikon D7000 occasionally has problems with. The D7000 would still be my preferred choice for shooting large-field sports, given Nikon's excellent line-up of fast (super)telephoto lenses and the camera's more sophisticated AF Area options for tracking both regularly and irregularly moving subjects in C-AF mode - but that aside, the E-M5's AF system is at least as capable as the D7000's, not to mention that it delivers the same level of performance regardless of whether you're using the eye-level viewfinder or the rear monitor. The same cannot be said of the D7000 whose AF performance takes a hit as soon as you enter Live View.

In terms of movie recording, neither camera would be the professional's first (or even second) choice as both models lack a few key features like user selectable frame rates at Full HD resolution, fine control over audio levels or the ability to monitor the audio using headphones while filming. For casual videography (vacation, family, pets etc.) the Olympus OM-D E-M5 appears to be your better bet given its tilting screen, smoother AF during movie capture, and superior hand-holdability thanks to its excellent in-body image stabilisation system.

As far as still image quality is concerned, the Nikon D7000 has a slight edge but the difference between the two cameras isn't nearly as dramatic as you may have expected. At medium to high ISO settings the Nikon holds on to fine detail slightly better while producing somewhat tighter-grained noise but these small differences will only matter (if at all) when making really large prints on high-quality paper. Dynamic range at base ISO is very good with both cameras but if you need to dig really deep into the shadows the D7000 will give you better results (from raw) thanks to its larger bit depth. Speaking of raw, both cameras appear to have over a full stop of highlight headroom in the raw files, when compared to their JPEG output, which is already very good.

In summary, there's no clear winner - and that alone says volumes about how far compact system cameras have come in the last few years. That the Olympus OM-D E-M5 can hold its own against one of the most highly regarded prosumer/semi-professional DSLR cameras of recent years is a huge surprise. It also means that for those who are actually in the process of deciding which of these cameras to buy, the choice will boil down to personal preference and what they would like to use their new camera for. It's certainly a close-run thing, and if you have no vested interest in either system you'd be well-advised to try them both at the same time to see which control layout, user interface and feature set you prefer.

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