Real-World Raw Dynamic Range

Introduction

It can sometimes be a bit hard to read about 'Dynamic Range' or see test data and translate it into real-world impact. Here we demonstrate the processing latitude offered by the Raw files of the Canon EOS 7D II and Nikon D7000, which illustrates the two cameras' respective dynamic ranges. We do this by exposing each camera for the highlights, and then assessing the noise levels of shadows when they're brought up to visible levels.

The Raw dynamic range of a camera is defined by the difference between the brightest tone a camera can capture and the darkest usable tone that is not swamped in noise. While DxO provides rigorous measurements that put a number on this attribute, we visually show you what the difference in base ISO Raw dynamic range between the 7D Mark II and a class-leading APS-C camera - in this regard - looks like.

Our Methodology

We shot a moderately high dynamic range sunset scene with both the 7D Mark II and the Nikon D7000, without filters of any kind. Our choice of exposures for this test parallel how a landscape shooter may have shot this scene, and requires a bit of elaboration.

The best way to capture a high dynamic range scene in a single exposure is to 'expose to the right' (ETTR). Using this method, you give the camera as much exposure as possible until the brightest tones in the scene you wish to capture are just short of clipping in the Raw file. Not only does this ensure that highlights are preserved, it also ensures that other tones - mainly shadows and midtones - have a fighting chance despite the shorter exposure required to protect highlights. The more light you collect, the cleaner your tones are because you (1) minimize the risk of darker tones running into the noise floor of the sensor from too short an exposure, and (2) minimize noise inherent in the light itself ('shot noise', due to the random arrival of photons), which decreases or 'averages out', in a sense, the more light you collect. Hence ETTR philosophy champions giving the sensor as much exposure as you can, but not so much that you clip bright portions of the scene you wish to preserve.

Typically, when you then pull an exposed-for-highlights Raw file into your favorite Raw processing software, the shadows and midtones will be dark. This is largely due to the low dynamic range and brightness of most of our monitors these days, requiring us to push shadows in Raws exposed for the highlights just to make them visible. A comparison of the noise levels in these pushed shadow regions then gives one an idea of the dynamic range capabilities of the camera.

You can make this comparison in our widget below:

In the ETTR shots, we've captured Raw files using exposures that map the brightest tones in our scene to Raw values just short of clipping*. That is, 1/3 EV longer exposures on either camera clip the green channels in these clouds. We're essentially trying to 'fit' the dynamic range of the scene into the dynamic range of the camera by mapping the brightest tones we wish to preserve as close to clipping on the sensor as possible, but not further below it, for the reasons we gave above.

As you can see, this results in significantly underexposed JPEGs, but allows for the creation of images from Raw files that display the full dynamic range of the original scene on your monitor - via selective brightening of shadows while protecting highlights. Looking closely at detail in the shadow regions, it becomes apparent that the D7000 has better captured the darker tones - introducing noticeably less noise. That said, it's nice to see that the banding issues that have plagued previous Canon bodies (7D, 5D Mark III) appear to be minimal, which helps the usability of the 7D Mark II's shadows.

While there's a significant difference in quality of shadows of the ETTR shots between the 7D Mark II and the D7000, the difference becomes even more pronounced if the exposures are less well optimized by reducing exposure an extra stop. Tones that are almost unusable on the 7D Mark II continue to be quite acceptable on the D7000. Note also how the Canon looks considerably worse than its corresponding ETTR exposure while the Nikon looks only slightly worse. Why the discrepancy? The 1EV shorter exposure pushes some of the tones we wish to recover below the 7D Mark II's noise floor and are consequently heavily impacted by noise in comparison to the 1EV higher ETTR shot. The difference in noise between the two exposures is less pronounced with the D7000 since its lower noise floor (and hence greater dynamic range) means that a 1EV reduction in exposure doesn't suddenly push these tones into unacceptably noisy territory. This means it's still possible to pull these same tones into the final image with noise levels well below the extensive noise the 7D Mark II's underexposed shot reveals.

And this is important. Since all the exposure assessment tools on both cameras are designed to reveal JPEG exposure, they offer little help in assessing Raw exposure. In fact, the straight-out-of-camera JPEG from our ETTR shot showed clouds that appeared to be clipping, with the 1EV shorter exposure looking more promising in terms of preserving highlights. Hence, it's not at all unreasonable to expect a photographer to have chosen an exposure closer to our 'ETTR (-1 EV)' shots for this scene, in which case the D7000 would've sufficed, but not the 7D Mark II.

What does this mean?

Getting an optimal ETTR exposure is difficult and usually only best done via extensive bracketing. Given the difficulty of absolutely nailing an optimal exposure, the flexibility offered by a camera with greater dynamic range cannot be understated for situations such as these: they prove more tolerant of any 'mis-exposure' which, in fact, may not be a 'mis-exposure' at all when you're using the in-camera exposure indicators to judge your exposure with higher dynamic range scenes such as this one.

Furthermore, the additional dynamic range of a camera like the Nikon D7000 over the Canon EOS 7D Mark II not only provides greater tolerance for sub-optimal exposure, it also means that the camera will be able to do a better job when confronted with an even wider dynamic range scene than this one. Which we can assure you landscape photographers encounter often.

In summary: The 7D Mark II's base ISO Raw dynamic range capabilities, though improved over its predecessor and on par with the 5D Mark III, falls far short of what the competition offers and has offered for some time. If dynamic range is of utmost importance, a camera with lower noise architecture - and a larger sensor - will offer significantly better results at lower ISOs**.

*If you're curious, the brightest green pixels in the clouds in the Nikon shot have a 14-bit Raw value of 14,763, vs a maximum possible Raw value of 15,779 (clipped). Similarly, for the Canon, the brightest green pixels in the clouds have a 14-bit Raw value of 13,550, vs a maximum possible Raw value of 13,584 (clipped).

**Note that the dynamic range advantages of cameras with high base ISO dynamic range can extend to higher ISOs as well, where the 'ISO-invariance' of cameras like the D7000 allows you to purposefully underexpose the image by lowering the levels of ISO amplification. This gives you extra highlight headroom in accordance with the amount of reduction in ISO amplification. The 7D Mark II is not amenable to this type of shooting.