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Posts: 2
Registered: ‎04-28-2016
Message 1 of 5 (3,858 Views)

Auto DRO and shooting in RAW

I recently bought a Sony Nex6 and I generally shoot in RAW and process in Lightroom v. 6  Although I haven't any info on this, I discovered that the Auto DRO setting works when shooting in RAW.  In high contrast scenes there are very few attacks of the blinkies.  I'd like to know how DRO works and whether there are any disadvantages in using it when shooting, for example, landscapes.  Thanks in advance.

Posts: 2,114
Registered: ‎01-08-2015
Message 2 of 5 (3,834 Views)

Re: Auto DRO and shooting in RAW

[ Edited ]

DRO (Dynamic Range Optimization) increases the ISO setting for darker portions of an image, which lightens them slightly, while it lowers the ISO setting for brighter portions. The result is that a broader range of light to dark is captured within the same dynamic range of the camera.


The downside is that increasing the ISO also increases the image noise, though only for those darker portions of the image.


As an aside, DRO does not alter RAW images, which have a broader dynamic range anyway. But the DRO setting is recorded in RAW files, and will be implimented in Sony's post processing applications when RAW files are saved as JPEG, but not in other image editting applications like Adobe's Lightroom.


FYI, Nikon uses the same technology in what it calls "Active D-Lighting".

¹ The Lens is the Thing
² 'Full Frame' is the new 'Medium Format'
³ "One good test is worth a thousand expert opinions." - Tex Johnston, Boeing 707 test pilot.
Posts: 361
Registered: ‎04-04-2016
Message 3 of 5 (3,831 Views)

Re: Auto DRO and shooting in RAW

[ Edited ]

Good question as I'm not familiar with Sony raw files. From my own experience shooting in raw is to have an image file that has not been in-camera processed which would include converting the image to a compressed jpeg and whatever settings processes were applied to it. This leaves me wondering if Lightroom is reading the metadata and appling its own interpretation or is it the camera. I suspect the camera.


I don't use Lightroom anymore and the camera I have that can save raw is not a Sony so I'm limited in knowledge for that software and hardware. But in my mind a raw image file should be just that, raw. In other words if I want pure carrot juice it should be just that and nothing else added to it. If the camera is applying effect settings like DRO to a raw file, and you cannot turn off those baked in settings, then in my mind its no longer raw. For me that would be a disadvantage in my workflow. A raw file should be like a film negative but I admit I'm old school. But if you like the results then there's nothing wrong with that either. The camera is just a tool to make a final product.


As for how DRO works I'll leave that question to those that know but I'd like to find out as well so yes, good question. 


Edit: I see my question was answered while pondering. Smiley Happy



Posts: 2
Registered: ‎04-28-2016
Message 4 of 5 (3,779 Views)

Re: Auto DRO and shooting in RAW

Thanks for the replies and the explanation of how DRO works to adjust the dynamic range at the time of capture.  As mentioned, I shoot in RAW and a look at the histograms before any post processing takes place tells me that DRO works with RAW so I shall continue to use it when photographing high contrast subjects.  I can confirm that in Lightroom 6 it is not possible in post processing to select say level 3 DRO when the capture setting was, say level 5 DRO.   My view is that this doesn't really matter.  What does matter to me is that shooting with DRO enabled helps us to avoid blown highlights and black shadows without any texture. In other words it increases our chance of getting an acceptably exposed digital capture and so provides a sound basis for further enhancement of the image. 

Posts: 1
Registered: ‎01-10-2018
Message 5 of 5 (892 Views)

Re: Auto DRO and shooting in RAW

This needs a little explanation. DRO was developed by Dr Michael Tusch, of Apical Ltd, a London DSP developer working originally in motion picture and later in smartphone fields. The process is handled - or was originally - by the Apical IRIDIX chip, which Sony bought into along with most of the other DSLR makers unless they chose to emulate the algorithms in camera firmware. DRO can not change raw data, but it uses raw data as part of the image processing pipeline between A-to-D conversion (whether on-sensor or as a discrete stage) and JPEG conversion. It happens either in a separate DSP circuit/chip, or I think in recent Sony models, as a function of the LSI.


In order to analyse the image and apply regional brightness, threshold and contrast corrections to emulate human vision DRO+ or Advanced needs to start with an underexposed raw image - it can't pull back burned out (saturated, clipped) highlights and brighter tones. So when you set DRO, most noticeably at higher manual settings, this has the effect of exposing the image as if you were using ISO 200 when you are set to ISO 100 (the exact difference depends on the setting). This is why DRO+ can't be used at very high ISO settings and on earlier models was limited to a range of lower ones. You can see how it works by setting up a test scene and observing the auto exposure given by the metering with and without DRO+. With DRO+, you'll see slightly less exposure is given. The result is the 'dark' raw file which DRO+ needs to work its magic.

This is not an altered raw file. It does not have a changed dynamic range. It's really just an ISO-constant slightly underexposed raw file, and that is what you get in Lightroom or ACR. It is why the preview initially showing the bright DRO+ processed result changes to a dark preview if have LR/ACR/Bridge set to rebuild previews. Sony's own earlier software includes a simultion of DRO, but not the advanced analytical version called DRO Advanced or DRO+, which uses the Apical chip or derived firmware processing. It uses the basic DRO which is, simply, a different gamma curve. In 2018 most Sony cameras have s-Log movie settings, and these also use a dark raw file and a extended source dynamic/compressed output dynamic curve. The movie processing which gave Apical its head start during development fifteen years ago is not so relevant now as everyone wants dark, flat, cinema-experience adjusted colour palette movies not bright natural results.


So, if you shoot raw and enable DRO+, you only get the DRO+ in the JPEG. They can be quite dramatic and will even correct exposure errors. You don't get DRO in any form in the raw file, other than a metadata tag which can inform Sony software to use a simulated process. What you get is a slightly underexposed raw file, which is why using DRO+ can give you 'better highlight control' in raw. Since it is linked to the camera's metering, the degree of underexposure varies according to contrast range and the size and position (relative to focus points) of very bright highlights.

Here is an article from the first generation of DRO Advanced, as found in the A700 DSLR. Around this time I visited Apical's London HQ and interviewed Dr Tusch, but sadly for me, his company was entirely privately owned no chance of buying shares...

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