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Dynamic Range

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 Modes

The tone curves of all image modes are very similar. There are slight differences in contrast with Vivid being the most and Natural being the least contrasty. All modes clip at the same point in the highlights but there is some variation at the shadow end. The highlight-roll-off is very smooth.

In our test we found that the GXR/A12 never actually clips the highlights (due to some fancy JPEG processing which extrapolates highlight luminance data even when one or more channels has clipped in raw). The tone curve never hits 255 but nevertheless there is little or no additional detail in the last few steps. Therefore we determined the dynamic range figures 'manually' by looking at the data. However, we used the original data to plot the curves below to give you an idea what is going on in the camera's JPEG engine.

Contrast

The GXR features contrast settings (as a part of the monochrome images modes and the customizable image modes Setting 1 and 2) from 1 to 9 . As you would expect the 1 setting produces a flatter tone curve while the 9 setting results in a more extreme s-curve.

ISO Sensitivity and Dynamic Range

The GXR/A12 50mm's highlight range remains constant across the sensitivity range. However, the measured shadow range decreases as you increase ISO. This is mainly due to increased noise and noise reduction smearing.

Sensitivity Shadow range Highlight range Usable range
ISO 200 -5.5 EV 4.0 EV 9.5 EV
ISO 400 -4.9 EV 4.0 EV 8.9 EV
ISO 800 -4.9 EV 4.0 EV 8.9 EV
ISO 1600 -4.3 EV 4.0 EV 8.3 EV
ISO 3200 -3.7 EV 4.0 EV 7.7 EV

Dynamic Range compared

At it default settings the GXR with the A12 50mm camera module is doing a very good job. It offers the highest total dynamic range, and crucially also the highest highlight range, which, to many photographers, is more important than shadow range, in this comparison.

Camera (base ISO)
Shadow range
Highlight range
Usable range
Ricoh GXR/A12 50mm -5.5 EV 4.0 EV 9.5 EV
Leica X1 -5.2 EV 3.0 EV 8.2 EV
Panasonic GF1 -5.4 EV 3.1 EV 8.5 EV
Sigma DP2 -5.0 EV 3.8 EV 8.8 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).





RAW headroom

There is usually slightly more dynamic range to be obtained from RAW capture compared to in camera JPEGs (thanks to the use of a consumer-friendly tone curve in the JPEG conversion). There is typically around 1 EV (one stop) or so of extra information available at the highlight end in RAW files. The application of some 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.

Adobe Camera RAW's default is fairly contrasty and, as expected, produces less dynamic range than the out-of-camera JPEG. The best result we could achieve in ACR by applying some negative digital exposure compensation, reducing contrast and increasing brightness is an impressive 12.2 EV. There is 'only' approximately 0.5 EV additional highlight range but considering the camera's already very good JPEG highlight range this is not much of a problem.

  • ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Brightness 50, Curve Medium
  • ACR Best: Exposure -1.3 EV, Blacks 1, Brightness 80, Contrast -50, Curve Linear
Settings Usable range
JPEG 9.5 EV
ACR Default 7.0 EV
ACR 'Best' 12.2 EV

These measurements are in line with what we found in real world use. The GXR/A12 50mm combination is very good at maintaining highlight detail but if you accidentally overexpose a shot (like we did with the shot of City Hall below) some detail can be recovered through negative digital exposure compensation in RAW conversion. In our example an area of the image (the tower in the background on the left and the wall next to river) is quite heavily over exposed. Reducing the exposure by 2.0 stops in Adobe ACR recovered a good amount of detail but there is some loss of color information (channel clipping) on the roof of Tower Bridge.

Adobe Camera RAW default conversion Adobe Camera RAW with -2.0 EV digital comp.
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