Dynamic Range (contd.)

Create Style options

The graph below shows the dynamic range response from all of the A350's color Creative Styles. As you can see, with the exception of Vivid and Landscape, which overlap each other almost exactly, they all have slightly different tone curves but deliver similar amounts of dynamic range. The important point to note here is that no single Creative Style delivers more dynamic range than the 'Standard' mode and of course because of more contrasty responses some actually deliver less.

ISO Sensitivity and Dynamic Range

The dynamic range delivered is essentially unchanged by changes in sensitivity which is useful to know when out shooting. The apparent increase in dynamic range at high ISO is a quirk of the way we measure dynamic range (The results produced by the A350's noise reduction algorithms )

Sensitivity Shadow range Highlight range Usable range
ISO 100 -4.9 EV 3.6 EV 8.6 EV
ISO 200 -5.0 EV 3.5 EV 8.5 EV
ISO 400 -5.1 EV 3.5 EV 8.5 EV
ISO 800 -4.3 EV 3.6 EV 7.9 EV
ISO 1600 -6.8 EV 3.6 EV ~ 8.5 EV*
ISO 3200 -7.0 EV 3.5 EV ~ 8.5 EV*

*The smeared noise pattern of the A350 appears to be confusing our analysis calculations into believing that data is being recorded when the image itself has been reduced to a baseline level of smoothed-out noise. We do not believe any more information is actually being recorded than at lower ISO settings.

Dynamic Range compared

The dynamic range delivered by the A350 from its default tone curve is up with the best of its contemporaries. The ability to retain information in the highlights (above middle gray, approaching white), is much more useful for rendering a scene naturally than having more detail in the shadows because 'blown-out' highlights tend to be more distracting than loss of definition in dark regions of an image.

Shadow range
Highlight range
Usable range
Sony DSLR-A350 (ISO 100) -4.9 EV 3.7 EV 8.6 EV
Canon EOS 450D (ISO 100) -5.1 EV 3.6 EV 8.7 EV
Olympus E420 (ISO 100) -5.4 EV 2.8 EV 8.2 EV
Nikon D60 (ISO 100) -5.4 EV 3.3 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).

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 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 eleven stops (11 EV) of total dynamic range but only 0.8 EV of that is in additional highlight range, suggesting that the A350 is doing a good job of conveying the majority of captured highlight detail in its JPEGs.

  • ACR Default: Exp. 0.0 EV, Blacks 5, Contrast +25, Curve Medium
  • ACR Best: Exp. -1.66 EV, Blacks 0, Brightness + 99, Contrast -50, 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. 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 background but this soon turns into gray as one or more of the color channels clips.

Sony's Image Data Converter software has a tool called highlight color distortion correction that tries to provide a more color-accurate transition to highlights when not all of the color channels have 'clipped.' It's pretty effective but doesn't do quite such a good job of recovering all the possible detail. What these images really show, though, is that once you have managed to get the A350's JPEGs to clip, there's not a lot of additional headroom in the RAW files to recover much detail.

Playing around with several over-exposed A350 files shows that it's unusual to get any more detail back once you've changed the digital EV compensation by more than 1 'stop'.

Adobe Camera RAW
default conversion
Adobe Camera RAW
-2.5 EV digital comp.
Image Data Converter
-2.0 EV digital comp.

Adobe Camera RAW
default conversion
Adobe Camera RAW
-2.9 EV digital comp.
Image Data Converter
-2.0 EV digital comp.