Previous page Next page

RAW headroom

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 from the graph below the Adobe Camera RAW default is actually quite similar to the camera JPEG, if anything there's very slightly more highlight range. The best we could achieve (with some pretty extreme ACR settings) was just over 10 stops total dynamic range, and more importantly about a stop more highlight range (although with no guarantee of color accuracy in highlights).

  • ACR Default: Exp. 0.0 EV, Shadows 5, Bright. 50, Contrast 25, Curve Medium (Default)
  • ACR Best: Exp. -0.85 EV, Shadows 0, Bright. 70, Contrast -25, Curve Linear

WARNING: One thing to bear in mind is that 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. This can be seen fairly clearly in the examples below, on the right the negative digital exposure compensation has revealed some more detail in the sky but there is no color information so the sky suddenly turns from cyan to gray. You can also clearly see posterization of tones where the clipping has literally nothing to recover.

There's really not a lot of headroom in K20D files that have been over-exposed (though this isn't usually a problem given the K20D's metering, which if anything tends to expose for the highlights).

ACR default conversion ACR with -3.0 EV digital exp. comp.
ACR default conversion ACR with -2.0 EV digital exp. comp.
ACR default conversion ACR with -3.0 EV digital exp. comp.

D-Range mode (dynamic range expansion)

The K20D offers a dynamic range exansion option, which appears to adapt the applied tone curve to retain highlights better (at the expense of noise in the shadows). Enabling D-Range doesn't appear to change the exposure yet is only available from ISO 200 upwards which suggests the sensor's native sensitivity may be ISO 200, hence offering slightly improved dynamic range at that setting.

The results are subtle but visible both in our dynaimc range tests and real-world shooting.

D-Rng Off (ISO 100) D-Range On (ISO 200)
Previous page Next page