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Dynamic Range Optimization

One of the A100's unique selling points is its 'in hardware' Dynamic Range Optimization (we'll abbreviate to DRO). Firstly it's worth considering the naming of this feature, it does not produce additional dynamic range, the actual dynamic range of the camera system is limited by the range available from the sensor and at least from our experience the actual DR of images whatever the optimization setting is the same. What the A100's DRO does instead is aim to lighten shadow areas and maintain highlights. It does this in a different way depending on the setting.

Dynamic Range Optimization modes

  • Off: The camera carries out no dynamic range optimization.
     
  • Standard: The camera optimizes the image by automatically adjusting the tone curve used to the linear RAW data into the final image (hence the brightness / contrast).
     
  • Advanced: The camera optimizes the image by selectively adjusting the brightness of areas of the image, it 'masks' certain areas for lightening, others are darkened slightly. This can be thought of as a digital 'dodge and burn'. *

* This method appears to be very similar to systems implemented by other manufacturers, notably HP and Nikon. The main difference here is that Sony are doing it in hardware and therefore it's much, much faster (just 0.7 seconds). They're also applying it to the RAW data before it's converted to JPEG (some competitor systems apply to the image after it's converted to JPEG).

Dynamic Range Optimization limitations

Unfortunately the DRO feature isn't available in the following circumstances:

  • Any metering mode other than Multi-Segment metering
  • Manual exposure mode (M)
  • If in RAW or RAW+JPEG mode
  • Advanced mode can only be used at ISO 100, 200 or 400

I was most disappointed that you can't have DRO enabled when shooting RAW+JPEG and that Sony's "Image Data Converter SR" application doesn't include the DRO feature and hence can't replicate the camera's DRO from a RAW file. Additionally if you AE lock the optimization is applied as per the AE lock image, if you shoot continuously the optimization is remembered from the first image and applied to all subsequent images.

Examples

Below you will find four examples of the DRO system in its Off, Standard and Advanced modes. Some of these were taken hand-held and so aren't perfectly framed and the last example has slightly different exposure values but still demonstrates a difference.

In this example you can easily see the advantage of using the 'Advanced' mode, the color of the sky is maintained and shadow areas are lifted.

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Again, the Advanced mode works the best here with much lighter clearer shadow areas and well maintained highlights and sky color.

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In this example the advantages are less obvious, Standard mode produces the lightest portrait however does this to the loss of accurate sky color.

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In this example the exposure values are slightly different, in fact the 'Advanced' shot uses the fastest shutter speed and smallest aperture (which should lead to a darker shot), the selective brightening of the shadow areas really lifts the image.

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Conclusion

Overall I'm quite impressed with the A100's DRO feature, however I saw very little advantage in using the Standard setting and was disappointed that I couldn't use DRO in RAW+JPEG mode, nor that Image Data Converter has any DRO features. I sometimes felt that the Advanced mode had applied a slightly too conservative amount of adjustment and hence it would have been nice to be able to set the 'strength' of shadow brightening or highlight darkening.

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