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.
Custom Image options
The results are, unsurprisingly, exactly like those of the K200D. The Custom Image settings all use essentially the same tone curve, with the exception the Bright and Landscape modes. And, oddly enough, those are the settings that have contrast set above 0 by default. The contrast 0 setting produces a smoother roll-off at the top of the curve, so is more likely to make the most of the available highlight information.
ISO Sensitivity and Dynamic Range
The K2000 is pretty consistent in its treatment of image highlights, managing to render 3.1 stops of light above middle gray. However, Pentax's tradition of applying very little noise reduction means that at higher ISOs, our test measuring increasingly limited shadow range (It stops measuring when noise reaches a certain threshold). That limited highlight dynamic range means that you'll either have to underexpose your photos (which the camera is slightly prone to do in its automatic modes) or live with blown highlights.
|Sensitivity||Shadow range||Highlight range||Usable range|
|ISO 100||-5.8 EV||3.1 EV||8.9 EV|
|ISO 200||-5.7 EV||3.1 EV||8.8 EV|
|ISO 400||-5.7 EV||3.1 EV||8.8 EV|
|ISO 800||-5.7 EV||3.1 EV||8.8 EV|
|ISO 1600||-3.7 EV||3.1 EV||6.8 EV|
|ISO 3200||-2.7 EV||3.1 EV||5.8 EV|
Dynamic Range compared
The K2000 repeats what we saw with the K200D, a camera that struggles to stop bright areas of the image blowing out. Although the overall usable dynamic range is on a par with its APS-C peers, the low highlight dynamic range can mean that highlights appear more obviously blown-out than would be the case with the best of its competitors.
|Camera (base ISO)||
|Pentax K2000/K-m||-5.8 EV||3.1 EV||8.9 EV|
|Canon EOS 1000D||-5.2 EV||3.5 EV||8.7 EV|
|Sony Alpha 200||-5.1 EV||3.6 EV||8.7 EV|
|Olympus E-420||-5.4 EV||2.8 EV||8.2 EV|
|Nikon D60||-5.7 EV||3.3 EV||9.0 EV|
|Pentax K200D||-6.0 EV||3.0 EV||9.0 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). Its Auto settings, meanwhile, pull around an extra stop of highlight detail back in, but use a tone curve that is unlikely to result in a particularly pleasant image.
- ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Brightness 50, Curve Medium
- ACR Auto: Exp. -0.25 EV, Blacks 0, Contrast 0, Brightness 0, Recovery 12, Curve Medium
As the image below shows, there is some highlight detail that can be recovered and blended back into your image if you want. There's little additional detail beyond 1.5 - 1.85 stops and the color accuracy breaks down a long time before that.
|Adobe Camera RAW default conversion||Adobe Camera RAW with -2.0 EV digital comp.|
|100% Crop||100% Crop|
Playing around with Camera RAW showed that around 4 stops above middle gray is the most you can sensibly recover. Here is the graph of the tone responses we got when pushing our dynamic range test sample, compared to RAW. We've then adapted the 'pushed' conversion to make an over-exposed image look acceptable and show it alongside the original JPEG. As you can see, it is possible to pull some extra detail from the RAW headroom into the image, by pulling around the image brightness and using a more sensible tone curve, without it starting to look ridiculous.
- ACR Realistic: Exp. -0.95 EV, Blacks 0, Contrast -7, Brightness +85, Recovery 0, Curve Medium
|Default JPEG||Our 'realistic' exposure settings|
|100% Crop||100% Crop|