D800 ADL

Started Dec 26, 2012 | Discussions thread
Jack Hogan
Veteran MemberPosts: 4,026
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Re: D800 ADL - recommended
In reply to Robin Casady, Dec 29, 2012

Robin Casady wrote:

Jack Hogan wrote:

Robin Casady wrote: how do you lean the gory details of how ADL works? Without knowing the algorithms, how do you know?

There are two key ingredients to ADL, as there necessarily need to be in any capture that eventually results in a pleasing image: 'good' recorded information in the raw data (this depends mainly on exposure) and 'good' processing of the captured data (this depends mainly on the in-camera engine and/or the artist's post processing prowess). Let's look at how ADL affects both.

1) Exposure. In an all manual setup you are the boss. If on the other hand you trust your metering to the camera, say in matrix mode, ADL will evaluate the scene and if it deems that the dynamic range of the scene is likely to exceed the dynamic range of the output device (as symbolized by the OOC Jpeg) it may decide to adjust exposure, backing off the highlights by up to 1 stop in order to preserve them - if needed and if it can be done given the other camera settings/constraints. It can do this with confidence because, in the case of Exmor-class sensors as found in the D800, it has plenty of Photographic Dynamic Range to play with: if by changing exposure it dedicates an additional stop in the raw data to tones above middle gray (bringing Middle Gray to typically 4-4.5 stops below saturation) it still has 7 stops for tones below it, plenty more than in the past - to keep noise under check in the deep shadows or to correct the odd mistake.

So at worst ADL does nothing to exposure, at best it saves highlights from clipping. What's there not to like?

2) Processing. Having captured (through manual or automatic exposure, also as above) a most excellent set of raw data the in-camera processing engine and the hapless photographer have the task of turning it into a pleasing, typically 8 bit, output. In the past this was mainly accomplished through brightness and contrast curves in-camera - and that was fine when DSLRs had PDRs of 8 or 9 stops (most DSLRs before Exmor, and most Canons today). But with Exmor-class PDRs of 11.5 stops the issue arises as to what to do with the additional data. Is a curve really the best way to squeeze 11.5 stops of information into 8 (I am simplifying, but you get the idea)? Of course not: there are a number of very good adaptive algorithms that exploit Human Visual System's characteristics out there that do a much better job than curves. The processing by ADL happens to use one of those. So most times ADL processing results in a more pleasing tone distribution of the OOC image than otherwise. Did I mention that it's just processing of the rendered data and that therefore if for whatever reason you do not like it or want full manual control you can simply turn it off in post and revert to good ol' curves or whatever you feel appropriate (as long as you shoot raw)?

So most of the time ADL processing will give you a better OOC image and starting point in post (C/VNX2 only). If you don't like it you can turn it off (always turned off in ACR/LR et al). What's there not to like?

It seems like a win-win to me, if you know how and when to use it

Jack

None of this answers my question. How do you know Thom's knowledge of ADL is wrong and yours is right?

Let me remind you of what I actually said:

"You seem to put a lot of weight on Thom's opinions, so you may just want to go along with what he says. On the other hand I believe my namesake's opinions on how Nikon's DSLR expose are dubious at best."

I have outlined why I think that in this thread.

You have just given a vague description of ADL with no details about how the ADL is processing the data. If you are going to make the claim that Thom doesn't know what he is talking about, you need to back that claim up with facts, not BS.

Only Nikon knows what code they use. I have given you a user's perspective. If you do not like this perspective ignore it and just do what you've always done.

You seem to have dropped your suggestion of using it with spot metering.

Not at all, I was simply trying to cover the two extremes: manual and fully auto. Spot metering is what I use 90% of the time - with ADL on Auto - and with surprisingly good OOC results :-)[smile]

Constructive Jack :-)[wink]

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