a while back you mentioned in an article on photoclubalpha, the A700 would underexpose the RAWs, when DRO is enabled.
Being a RAW shooter I found it disappointing that this meant, DRO was unusable for me. Luckily I've did my own experiments with RAW+JEPG a while back and to my surprise couldn't see a difference in the RAWs with DRO on or off. I've started a thread on DPR asking others about their experience, but unfortunately no-one seemed to have done his own tests.
Afterwards the story of DRO underexposing the RAWs appeared in several threads on DPR and quite some other forums (even German ones) and even Garry Friedman gave a reference to it in his A700 ebook. I've replied to each of them asking, whether the poster tried it himself or just quoted from your article and no one ever stated, he had seen the underexposure himself. Meanwhile some others did their own test and confirmed my observation, that the RAWs were absolute identical with DRO on or off. Since then I started to disbelief your DRO RAW underexposure theory and called it one of the most believed myths of the A700.
David, I would have liked to see you participate in one of these threads on DPR, and actually invited you via email to one a while back. As you are banned on DPR now, this is not possible. Thus I open this thread on photoclubalpha to discuss your theory here.
May I start with a reply I've given to one of the last threads about this on DPR:
Shooting RAW+JEPG is the only alternative for a RAW shooter to use DRO. My impression is, that a lot of A700 users stay away from using DRO with RAW+JEPG solely because of your article, which would be sad, if the facts don't hold true. And so far no-one including myself was able to find a proof for your theory.> However, the fact is that DRO CAN cause the RAW to be underexposed,
> and David's example shows that. In order for DRO to work, in some
> circumstances it will underexpose the shot as with his first example.
Yes the RAW in David's example is underexposed. But I have a problem with David's conclusion, it is DRO that is the reason for this. He didn't take the same scene with DRO off (at least he didn't say so). He just assumed, the RAW would have been exposed differently with DRO off.
But look, there are these bright windows in the background. Couldn't they have thrown-off metering and led to the underexposure, whether DRO was on or not. David might have been mislead to held DRO responsible for the underexposure, because it fitted nicely into his theory. It is always dangerous to derive a statement without having tested it thoroughly.
When we speak about underexposure, we must differentiate between a technical underexposure, i.e. the camera exposes less than it would do without DRO enabled, and the perceived underexposure, the scene looks too dark to our eyes.
Both the RAW pictures of David and William show a perceived underexposure. You need to dial in +EV when shooting to make them look good and you probably won't do this with DRO on, because the preview and histogram give you the impression, the perceived exposure is correct.
So yes, DRO could lead to an underexposed RAW, because it might trick you in not overriding automatic exposure with +EV, like you would do normally.
But no, DRO doesn't change automatic metering on the RAW in a gain-based way, like David assured in his article.
Or in other words: It is not the camera but the photographer, who is responsible for a possible underexposure with DRO on.
I'm really interested, whether you investigated more into this question after your initial article and whether you know of a reproducible setup to show the DRO RAW underexposure.
Cecco
