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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?

  • Peripheral comment: be VERY careful when using DRO with flash. It has very good and very bad aspects: It can be immensely useful with eg a long table of people where the flash lighting drops as inverse square and exposure levels at the near and far end are vastly different- DRO can do an excellent job of balancing the apparent illumination levels so the scene is (apparently) much more evenly lit. | HOWEVER: When used on groups of people it can vastly wash out details on skin tones in high illumination area. People with darker faces may end up with "coffee coloured slabs" in place of skin ... – Russell McMahon Jul 14 '16 at 1:43
  • ... images. I found this out the hard way with my A77. DRO is still useful in such cases but due care is needed.| Higher numbered DRO levels adjust lighting more aggressively in areas of different illumination. DRO 5 will create the most evenly illuiminated images at the cost of loss of reality. || If shooting a scene where you wish to maintain or emphasise high contrast, turn DRO off. True black is often impossible to obtain with DRO on as it sees black as an opportunity to adjust effective dynamic range. – Russell McMahon Jul 14 '16 at 1:44
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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.

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  • Does it reduce only exposure (time? aperture?) to retrieve details from the highlights? Or does it shift the whole available dynamic range? Where did you find this information? – Count Zero Apr 24 at 12:18
  • Generally, it chooses to reduce exposure slightly. That depends on the exposure latitude of the sensor and data obtained from metering sensor, so on some scenes the shutter-speed could be increased, while on others not. Personally, I almost always shoot in A and with fixed ISO, so maybe it could change those parameters if they were free. There might be differences between cameras but I've tested this on fewer than 10 Sony models. On the A7R IV, the exposure hasn't moved among the few tests shots taken. I conferred with Sony Expert Gary Friedman to validate this. – Itai Apr 24 at 15:39
  • That's interesting and might be the case for A-priority mode. I doubt it's the case e.g. in manual mode. Where did you get that information? Or is it just something you think happens based on experience? – Count Zero Apr 24 at 15:45
  • Manual with fixed ISO, nothing could be changed. I doubt it does but I will try it later or this weekend. Yes, I have seen it happen but because the A7R IV is more complex and allows the tone-curve to be finely controlled, I wondered how this interacted with DRO and so I discussed it with Gary Friedman who is a known expert on Sony cameras (as opposed as my expertise on image processing since 20+ years and general digital camera reviewer for 15 years). – Itai Apr 24 at 18:37
  • Thanks for the clarification, @Itai ! – Count Zero Apr 24 at 19:24
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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.

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    "from sunlight at the beach to black cats in coal mines" I'm pretty sure regular human eyes do not have this amount of dynamic range. They often require to adjust to the different light levels even from regular sunny daylight outside to indoor light in buildings, let alone coal mines. – null Jul 13 '16 at 20:50
  • Caution using the term "exposure" when discussing the effects of changing the f/stop. That's aperture. There is a relationship of course, but "exposure" often means "exposure time". – Lightness Races in Orbit Nov 20 '19 at 11:18

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