Our Dynamic Range measurement system involves shooting a calibrated Stouffer Step Wedge (13 stops total range) which is backlit using a daylight balanced lamp (98 CRI). A single shot of this produces a gray scale wedge from (the cameras) black to clipped white (example below). Each step of the scale is equivalent to 1/3 EV (a third of a stop), we select one step as 'middle gray' and measure outwards to define the dynamic range. Hence there are 'two sides' to our results, the amount of shadow range (below middle gray) and the amount of highlight range (above middle gray).
To most people highlight range is the first thing they think about when talking about dynamic range, that is the amount of highlight detail above middle gray the camera can capture before it clips to white. Shadow range is more complicated; in our test we stop measuring values below middle gray as soon as the luminance value drops below our defined 'black point' (about 2% luminance) or the signal-to-noise ratio drops below a predefined value (where shadow detail would be swamped by noise), whichever comes first.
Picture Style options
As we have seen on previous Canon DSLRs the various Picture Styles use either one of two tone curves, the first more contrasty curve for Standard, Portrait, Landscape and Monochrome Picture Styles and a slightly flatter curve for Neutral and Faithful Picture Styles. Neither curve delivers more dynamic range and they both clip highlights at the same point.
Image Highlight tone priority
The Highlight Tone Priority feature is designed to deliver more highlight range. It's available via C.Fn II-3 and, once enabled, the usable ISO range becomes ISO 200 - 6400 (ISO 100 and 12800 are no longer available). In this mode the camera must be applying slightly less gain than normal combined with a different tone curve to deliver approximately a stop more highlight range, though as our real world examples later in the review show, don't expect miracles.
ISO Sensitivity and Dynamic Range
Although noise cuts the shadow range at the very highest ISO settings the EOS 7D's JPEG dynamic range is pretty consistent up to ISO 3200. The range - around 8.3 EV - is fairly typical for a camera at this level.
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-5.0 EV||3.3 EV||8.3 EV|
|ISO 200||-4.9 EV||3.4 EV||8.3 EV|
|ISO 400||-5.1 EV||3.3 EV||8.2 EV|
|ISO 800||-4.9 EV||3.4 EV||8.3 EV|
|ISO 1600||-4.8 EV||3.4 EV||8.2 EV|
|ISO 3200||-4.3 EV||3.5 EV||7.8 EV|
|ISO 6400||-3.4 EV||3.5 EV||6.9 EV|
|ISO 12800||-3.0 EV||3.5 EV||6.5 EV|
Dynamic Range compared
The EOS 7D's overall performance is pretty much in line with the competition in this test. Having said that at 3.3 EV the new Canon delivers slightly less highlight range than the EOS 50D (3.5 EV) and the Nikon D300S (3.8 EV). The Pentax K-7 measures the highest overall dynamic range but at 2.9 EV delivers almost half a stop less highlight range than the EOS 7D, with little rolloff and therefore harsh clipping.
|Camera (base ISO)||
|Canon EOS 7D||-5.0 EV||3.3 EV||8.3 EV|
|Canon EOS 50D||-4.8 EV||3.5 EV||8.3 EV|
|Nikon D300S||-4.6 EV||3.8 EV||8.4 EV|
|Pentax K-7||-5.7 EV||2.9 EV||8.6 EV|
The wedges below are created by our measurement system from the values read from the step wedge, the red lines indicate approximate shadow and highlight range (the dotted line indicating middle gray).
Experience has told us that there is typically around 1 EV (one stop) of extra information available at the highlight end in RAW files and that a negative digital exposure compensation when converting such files can recover detail lost to over-exposure. As with previous reviews we settled on Adobe Camera RAW for conversion to retrieve the maximum dynamic range from our test shots.
As you can see the default Adobe Camera RAW conversion delivers less dynamic range than JPEG from the camera (a more contrasty tone curve). The best we could achieve was just under 10 stops (9.8 EV) of total dynamic range, more importantly just over a stop of that is in highlights. This is pretty much in line with other cameras in this class.
|JPEG Default||8.3 EV|
|ACR Default||7.0 EV|
|ACR Auto||9.6 EV|
|ACR Manual||9.8 EV|
Please note that our version of Adobe ACR (5.6 Beta) had not been fully optimized for the EOS 7D yet which leads to strong color cast when attempting to recover highlights. We have therefore decided to not include any real-life samples at this stage but will update this section once a final version of ACR 5.6 is available.