My Sony Alpha 77 has a DRO mode, which is on by default and I have been using it most of the time. I understand that it aims to improve dynamic range much like HDR, without actually needing multiple exposures, but what does it do exactly as in how does it work, and am I losing anything if I keep it on and shoot in raw? Also what are the different settings for, Auto and +1 to +5?
DRO stands for Dynamic Range Optimization. It is designed to fit more dynamic range into images. A single exposure is still taken so you are always limited to the sensor's latitude. However, from what the sensor captures, more or less of that range is mapped into images. With fixed values, the transform is applied the same to each image. With Auto, it depends on feedback from the metering system and the mapping from sensor dynamic-range to images will be adjusted accordingly.
DRO is one of the few settings which indirectly impacts RAW files. While its designed as processing, which normally effects JPEG and TIFF files only, the camera adjusts exposure to have more dynamic range available for the mapping, often reducing exposure to get more details in highlights. If you shoot RAW and Manual mode though, DRO will have no effect.
Our eyes can see over a super broad range of light levels from sunlight at the beach to black cats in coal mines. The cameras, as a general rule lacks this ability.
In photography we use the f/stop as a unit that expresses exposure. The f/stop system is base on a halving or doubling of the light that is allowed to play on the camera’s digital sensor. When we talk about the light level range that a camera can record, we name this action “Dynamic Range".
The typical film camera has a Dynamic range of about 10 f/stops. Since each f/stop measures a 2X change in light level, we are taking: 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 X 2 = a 10 f/stop range = 1:1024 light level ratio. Can we image an automobile’s gleaming chrome trim, the automobile’s body, and the black tires and make an image with details in all? The answer is maybe, but this is a difficult task. If you were required to show detail in the tread of the back tires in shadow, maybe an impossible task.
All this -- we are taking about is dynamic range. We can get X more stops of range if we apply different techniques. Your camera features DRO which stands for Dynamic Range Optimization. This is an electronic app that attempts to matches the human range of vision for dim and bright subjects. It automatically lightens shadows as it adjusts the exposure for the highlights.
It’s a good thing! Sony calls it DRO, others Intelligent Dynamics, still others Active D-lighting.