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.
Picture Style options
As we have previously seen 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
One feature new to the EOS 450D (and inherited from high end models such as the 1DS and 40D) is Highlight Tone Priority, designed to deliver more highlight range. It's available via C.Fn II-5 and, once enabled, the usable ISO range becomes ISO 200 - 1600 (ISO 100 is no longer available). In this mode the camera must be applying slightly less gain than normal combined with a different tone curve to deliver almost a whole stop (0.9 EV) 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 a little at IS0 1600 the EOS 450D's JPEG dynamic range is pretty consistent across the range, and offers a marginal improvement over the EOS 400D (mainly in the shadow region - made possible, we'd guess, by slightly more aggressive noise reduction). The range - around 8.7 EV - is fairly typical for a camera at this level (and isn't far off what you get from the EOS 40D).
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-5.1 EV||3.6 EV||8.7 EV|
|ISO 200||-5.1 EV||3.6 EV||8.7 EV|
|ISO 400||-5.1 EV||3.6 EV||8.7 EV|
|ISO 800||-5.0 EV||3.6 EV||8.6 EV|
|ISO 1600||-4.7 EV||3.6 EV||8.3 EV|
Dynamic Range compared
The EOS 450D is one of the better performers in this test, though there's not a lot between any of the cameras here. The Sony Alpha 350 has the best highlight range, giving almost a stop more than the worst performer, the Olympus E-420. As the graph below clearly shows the EOS 450D is almost identical to its predecessor, with the only significant difference being a touch more shadow range.
|Camera (base ISO)||
|Canon EOS 450D||-5.1 EV||3.6 EV||8.7 EV|
|Sony Alpha 350||-4.9 EV||3.7 EV||8.5 EV|
|Nikon D60||-5.7 EV||3.3 EV||9.0 EV|
|Canon EOS 400D||-4.9 EV||3.5 EV||8.4 EV|
|Olympus E-420||-5.4 EV||2.8 EV||8.2 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 and less noise reduction in shadows). The best we could achieve was just over 10 stops (10.2 EV) of total dynamic range, more importantly almost a stop of that is in highlights (although with no guarantee of color accuracy). This is pretty much the same as the EOS 400D and around 2/3 stop less than the EOS 40D.
- ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Curve Medium
- ACR Auto: Exposure 0.0 EV, Recovery 25, Brightness +7, Curve Medium
We were actually pretty impressed with the EOS 450D's RAW files when it came to recovering detail from highlights that would be clipped in JPEG shots. Even with 3 or 4 EV of negative 'digital exposure compensation' applied we got perfectly usable results, though obviously if you really push the files (such as with the second and fourth examples here) you'll start to lose color information and will eventually see posterization.
That said, using ACR to rescue shots such as these produces remarkably good results most of the time and clearly shows the advantages of shooting raw. Whether the new 14-bit processing helps or not we can't know for certain, but in theory it should produce smoother gradation and greater pliability when pushing or pulling badly exposed shots.
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