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 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.
Highlight Tone Priority
In common with all of the latest generation of EOS SLRs the 5D Mark II sports Canon's new Highlight Tone Priority setting, 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 is no longer available). The highlight tone priority function uses a different tone curve to achieve about one stop more dynamic range in the 'on' setting compared to 'off'. There is no noticeable difference in shooting speed, so even though the default setting is off, it is feasible to leave it on all the time, especially when shooting JPEGs. Interestingly once you enable HTP you get essentially the same tone curve as the Sony Alpha 900.
As we have seen in other current generation EOS cameras, the various Picture Styles use either one of two tone curves, the first more contrasty curve for the Standard, Portrait, Landscape and Monochrome Picture Styles, and a slightly flatter curve for the Neutral and Faithful Picture Styles. Neither curve delivers more dynamic range and they both clip highlights at the same point.
The graph below shows how the camera's tone curve and dynamic range is affected by the wide range of contrast settings. The lowest contrast setting (-4) is almost linear for at least two thirds of the range and offers the widest dynamic range, but only by a whisker.
ISO Sensitivity and Dynamic Range
The EOS 5D Mark II has an indicated base sensitivity of ISO 100 and the top calibrated setting of ISO 6400 (ISO 50 is indicated as 'L', ISO 12800 is indicated as 'H1', ISO 25600 is indicated as 'H2'). As you can see from the graph below the compromise at ISO 50 is highlight range, which falls to 2/3 of a stop (0.7 EV) short of that seen from ISO 100 upwards.
Using the default JPEG settings the Mark II delivers somewhere in the region of 8.4 stops of dynamic range from ISO 100 to 3200, dropping 2/3 of a stop at ISO 6400, a further stop at ISO 12800, and finally another stop at ISO 25600.
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 50*||-5.1 EV||2.6 EV||7.7 EV|
|ISO 100||-4.9 EV||3.5 EV||8.4 EV|
|ISO 200||-4.9 EV||3.6 EV||8.4 EV|
|ISO 400||-4.9 EV||3.6 EV||8.4 EV|
|ISO 800||-4.9 EV||3.6 EV||8.4 EV|
|ISO 1600||-4.8 EV||3.6 EV||8.4 EV|
|ISO 3200||-5.1 EV||3.4 EV||8.6 EV|
|ISO 6400||-4.4 EV||3.5 EV||7.8 EV|
|ISO 12800*||-3.4 EV||3.4 EV||6.8 EV|
|ISO 25600*||-2.4 EV||3.4 EV||5.8 EV|
* Non-standard sensitivities
Dynamic Range compared
There's not a lot of difference between the usable dynamic range of all the cameras listed here, with the exception of the Sony A900, which is about a stop better than the rest . The other 4 cameras all offer usable dynamic range around the 8.4 stop region (the Nikon D700 has a little more highlight range than the 5D Mark II, but the overall range is very close). The original 5D still holds up well 3 years after it was first introduced. As mentioned above, enable Highlight Tone Priority and the 5D Mark II matches the A900.
|Canon EOS 5D Mark II (ISO 100)||-4.9 EV||3.5 EV||8.4 EV|
|Sony Alpha A900 (ISO 200)||-5.1 EV||4.2 EV||9.4 EV|
|Nikon D700 (ISO 200)||-4.4 EV||3.4 EV||7.8 EV|
|Canon EOS 5D (ISO 100)||-4.7 EV||3.5 EV||8.2 EV|
|Canon EOS-1Ds Mark III (ISO 100)||-5.1 EV||3.5 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 to 2 EV (one or two stops) 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.
The default Adobe Camera RAW conversion delivers less dynamic range than JPEG from the camera (the same contrasty tone curve and very little noise reduction in shadows). Simply switching to 'Auto' in the ACR conversion dialog reaps huge rewards, increasing the dynamic range to around 10.3 stops which is almost two stops better than JPEG.
- ACR Default: Exp. 0.0 EV, Blacks 5, Brightness +50, Contrast +25, Curve Medium
- ACR Auto: Exp. -1.05 EV, Recovery 9, Brightness 0, Contrast 0, Curve Linear
- ACR 'Best': Exp. -1.45 EV, Recovery 0, Brightness +50, Contrast -37, Curve Linear
WARNING: Although ACR was able to retrieve the 'luminance' (brightness) of wedge steps which were previously clipped there's no guarantee of color accuracy as individual channels may clip before others. The best we were able to get out of the file was 11.1 EV total range, though as the graph above shows, most of this is at the shadow end.
Although it won't bring back grossly overexposed shots the 5D Mark II's sensor allows somewhere in the region of one and a half stops of headroom to recover highlights - this is on a par with most DSLRs but not as good as, for example, the Nikon D3 or D700 - or the Sony Alpha 900. The examples below show this clearly - areas that appear clipped in the JPEG are more often than not also clipped in the raw file, but you do have a little room to play with areas of overexposure.
|Adobe Camera RAW default conversion||Adobe Camera RAW with -2.0 EV digital comp.|
Below is an example where a part of an image is grossly overexposed and highlights are heavily clipped. While a little of the detail is recovered from RAW in the shadow of the overhang of the building, the rest is completely lost and unrecoverable no matter how far you push the negative exposure compensation. Note that at two stops negative compensation you can no longer be guaranteed color accuracy, with some channels clipping earlier than others.
|Adobe Camera RAW default conversion||Adobe Camera RAW with -4.0 EV digital comp.|