Poll, what do you think Active D Lighting does to a RAW file?

Discussion in 'Nikon DX DSLR' started by Triggaaar, Jul 7, 2008.

  1. Nothing, it only affects NEF file and therefore the way the RAW is processed by CNX

    16 vote(s)
    31.4%
  2. The Low, Normal and High setting all have the same effect on the exposure of the RAW file

    1 vote(s)
    2.0%
  3. The exposure of the RAW file can be affected by varying amounts, depending on which level you chose

    34 vote(s)
    66.7%
  1. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    Firstly, this is about ACTIVE dynamic lighting, as opposed to the Dynamic Lighting available in software.
    Secondly this is about the effect of ADL on RAW files only, not JPEGs.

    I've read through a dozen separate threads on D-Lighting and there seems to be no consensus of opinion on what it does, at even a basic level. Many have tried to do tests, but come up with different results. I think a poll will help us come to a consensus on what it really does.

    Because non Nikon software like Lightroom cannot process camera info contained in NEF files in the same way Capture NX can, some believe that Active D-Lighting does not have any affect on any RAW images. Similarly, some believe you should leave it on low (or normal) because that allows you to adjust it, or switch it off completely in CNX - although that is true, some believe suggesting that switching it off in CNX is the same as having never had it on in the first place (ie, no affect on the RAW image).

    I will just give a little more detail on what I mean by each choice:
    1) Nothing, it only affects NEF file and therefore the way the RAW is processed by CNX
    If this is the case, and you use non Nikon software to process RAW files, it doesn't matter what you have the camera set to. If you use CNX, you may as well leave the camera ADL on, because this allows you to adjust it with CNX (you do not have the choice to adjust it in CNX if it is set to 'off' on the camera).
    2) The Low, Normal and High setting all have the same effect on the exposure of the RAW file
    If this is the case, you should be more careful about its use, as it can cause shots to have less exposure (to avoid cliping highlights) than if it was off. But whether you set it to Low, Normal or High will only have an effect on your post processing work level (because you can adjust it), not on the actual RAW file produced.
    3) The exposure of the RAW file can be affected by varying amounts, depending on which level you chose
    If this is the case, you should be EVEN more careful about its use, as an inappropriate setting will affect the quality of your image (the exposure of your image could be further from ideal, and fixing with post processing will cause more noise etc).

    From reading the different threads (I don't have a D300 yet), I believe that the reality is 2):
    In cases where you have no highlights cliping, it will not vary the exposure (this seems to be the case in some tests I've seen). In cases where some highlights would be cliped, the ADL reduces the exposure to stop them clipping (regardless of whether it's set to Low or High). The low/normal/high setting then affects how much processing the camera applies to the NEF (eg how much detail to bring out of shadows), but this can also be done in CNX, with the same results. Switching ADL 'off' in CNX will not be the same as having it 'off' in the camera, because the RAW files 'may' have been exposed less.

    Please post your findings and lets see if we decide what we are supposed to do with this setting.
    Thanks
     
  2. pforsell

    pforsell

    Jan 15, 2008
    It lowers the exposure. I think I read in Thom Hogan's that the amounts were 0, 0.3 and 0.7 stops with low, normal and high respectively.
     
  3. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    That doesn't sound too clever. If that was the case, it would be best to have it set to low at a minimum (unless needing high fps), since you'd be able to turn it off in CNX with no adverse affect to leaving it off in the first place, but it would give the advantage of having the option to use ADL in PP.

    I'd have thought it was more intelligent, eg using Matrix metering to ensure you don't lose any highlights. If it's simply fixed stops under exposure (plus the processing details in the NEF), it may as well leave us to do the exposure with exp compensation.

    I can't find info on Thom's site, does he talk about it in his books?

    I hope you're wrong Peter, that sounds rubbish :) 
     
  4. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    From DPreview of the D300:
    http://www.dpreview.com/reviews/nikond300/page16.asp

    "Rather than only adjusting the shape of the tone curve (as most similar systems do) setting higher levels appears to apply a third of a stop negative exposure compensation (typically slightly higher shutter speed)"

    Just reading that sentence, it's not clear if it adjusts the exposure depending on how high the setting is, but looking at their tests ('off' vs 'high'), Active DL didn't reduce the exposure by any more than 1/3rd (as opposed to the 0.7 that Thom suggests).


    An example from the D3 review was a landscape shot in jpeg, and the exposure was reduced by 0.6:
    1/1000 sec F7.1 (ISO 200) 1/1600 sec F7.1 (ISO 200)
    I'm not sure why that's more than the test with the D300
     
  5. yamo

    yamo

    Jun 28, 2007
    Santa Cruz, CA
    Triggaaar,

    Greetings. Good luck in figuring this out. I looked at this enough to satisfy myself that having ADL set at any level didn't effect the RAW file enough to show a remarkable difference for converting with Lightroom. It does offer some tonal choices in CNX that I happen to like so I shoot with ADL on low most of the time. This does have the effect of lowering Continuous shooting speed.

    I did not have the same experience with my tests as above, so go figure. It would be strange for ADL to change shutter speed (then does ADL not work if you set everything manually?).

    In any event, since this feature has been around since December, and I've yet to read the definative piece on what it does. I'm inclined to go with what I've seen in my shots, which is I like it on Low. Most of the shots that I process, I end up using the Low setting.

    As always, ymmv.

    Cheers,

    -Yamo-
     
  6. TonyBeach

    TonyBeach Guest

    Shooting in Manual exposure mode ADL does nothing. Using Aperture Priority it will change the EV, sometimes so subtly that you will not see it in the EXIF data -- the camera can choose a shutter speed anywhere between 1/320 and 1/400, but it will only show the shutter speed closest to the one selected by the camera in the EXIF data; if you use Shutter Priority, the change will be to the aperture; if you use Manual and Auto-ISO the difference will be to the ISO. ADL is intended to be used in conjunction with Matrix metering and one of the "auto" exposure modes, that's when it has the most dramatic effect on exposures.
     
  7. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    Hi Yamo. Like I said I searched the forum for info before starting this thread and most of what I found was written by you :) 

    Well Tony says ADL doesn't do anything when set to manual. I assumed that when set to manual, it would adjust the meter reading to be more conservative (note, this is only when using matrix metering on a shot with a wide dynamic range, where highlights would usually be blown) - so in effect, it would be the same whether using manual or not, but you would have to adjust the shutter/ap/iso according to a new reading.

    This should be easy to test indoors. Just put the camera on a tripod and create a wide dynamic range for the shot (put a portable light to one side of the picture). And take a shot with matrix metering, aperture priority, with ADL off, low and high (normal if you like too). Check that the shot does clip a good amount with ADL off. Then you don't even need to see what the results look like, just see what the sutter speed is for each shot (taking note of what Tony said about the exif data only showing approximate speeds).

    If no one else manages this before October, I'll do it when I eventually upgrade.
     
  8. jhwalker

    jhwalker

    61
    Jun 10, 2008
    United States
    Easy . . .

    ADL underexposes from 0.3 - 1.0 stops and applies a custom tone curve to lift the shadows, effectively compressing the dynamic range. You can easily see this by shooting the same shot with Low, Medium and High ADL. In all the test trials I've done (not exhaustive, of course), Low underexposes by 0.3 stops, Medium underexposes 0.7 stops and High underexposes by 1.0 stops - this is pretty consistent.
     
  9. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    You say easy...

    Thanks Jonn. It's just strange that that's not what happened in any of dpreviews tests (as I linked above), where High only underexposed by 0.3 stops vs Off. I'm just going to have to test it myself (just need that dam camera first). I wouldn't want to take a years worth of photos and then wish I'd set it differently (I regret not starting my digital journey with raw).
     
  10. TonyBeach

    TonyBeach Guest

    I haven't checked out DPR's review, but if they used Center-weighted than ADL's effect on EV is more muted than it is with Matrix.

    You can set ADL to low and then jack it up or turn it off later in NX, and using Center-weighted metering you will not take a big hit on the camera tending towards underexposure to protect the highlights. The D300 already has more DR than the D200 or D2x; the D3 has even more DR.
     
  11. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    I assumed they used matrix, as that's what I'd read you were supposed to use with it.

    Yeah I know you can change the setting, it's the original effect on the exposure (and therefore on the RAW image) that I'm concerned about. Thanks for the centre weighted tip - I will probably just start with it on low (too much else to think about with a new camera to be changing it regularly) to keep the effect on exposure to a minimum, and I'll be trying centre and matrix anyway (subject dependant).

    Not according to DPR: http://www.dpreview.com/reviews/nikond3/page20.asp
    They say that the dynamic range for the D3 and D300 are very similar (D300 a little better). Unless the detail at the extremes for the D3 is better?
     
  12. TonyBeach

    TonyBeach Guest

    I don't put much stock (or any for that matter) in this part of DPR's reviews. I'm still waiting for Thom Hogan's review of the D3. Regarding the D300 dynamic range he writes, "Whereas most of the previous Nikon DSLRs all were in the 7 to 7.5 stop range of usable dynamic range, I'll put the D300 squarely in the 8 stop usable range, perhaps even a bit more than that..." Now I recall that Thom has written 10 stops for the D3, but tracking down that is far too difficult right now, so I'll wait for his D3 review.
     
  13. Gary Mayo

    Gary Mayo Guest

    What's a raw file? LOL
     
  14. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    Well having finally upgraded (turned out to be a D700, not the D300) I've just done some tests.

    Yes, that's what he says in his D700 Guide. It's not the whole truth, but good enough.

    My testing, in RAW only.
    First test:
    Set-up on a tripod at a fixed seen with more dynamic range than the camera can handle (inc a lamp with a woven shade).
    Matrix metering, Dynamic AF area 51 point. Focused with AF-ON, and shutter focusing switched off. Aperture priority, fixed ISO.
    Active DL off - low - normal - high gave shutter speeds of 1/3 - 1/3 - 1/4 - 1/5
    Which equals 0 stop, 1/3 stop, 2/3 stop - as per Thom's guide.
    I reset the camera so the meter would select from a different part of the scene, and got shutter speeds of 1/6 - 1/6 - 1/8 - 1/10
    Which is exactly the same result.

    Second test:
    I repeated the test on a wall where the dynamic range in the scene was low, and got shutter speeds of 1/2.5 - 1/3 - 1/3 - 1/3

    Not as per Thom's guide. So ADL only reduces the exposure if it feels the need to, due to a high contrast scene. Which is handy if you accidentally leave it on, it won't ruin your RAW file (as you can remove any curve work with NX2).

    I'm not sure why the low setting caused the shutter speed to change in the second test (which I repeated again to check it was right) but not in the first test. Perhaps it's due to the way EXIF rounds shutter speeds, I'm not going to lose sleep over it.

    This does mean that if you shoot in RAW and process with NX2, and you'd like access to the ADL curves, it is worth using the low setting when shooting high contrast scenes , because it doesn't significantly affect the RAW data.
     
  15. yamo

    yamo

    Jun 28, 2007
    Santa Cruz, CA
    Mike,

    Greetings... Ah, nothing like reading an old thread (I said that? :wink:) ...

    I have shot probably in the range of 30,000 clicks with ADL on low, and adjusting in CNX... sometimes leaving on low, sometimes off and sometimes normal, almost never on high (makes me wonder what in the world someone would want with the extra high setting ... which I can now set for all those photos I shot with ADL on low)...

    But anyway, I eventually just turned it off. Nothing quantifiable at all, but I just got the feeling I was giving up some color depth with it on (and when I set it higher than low)... and ended up choosing to make the adjustments using the array of white balance and picture controls during conversion and saving other adjustments for post-processing.

    It's easier on my mental model of how the whole digital processing process works, if I can separate what happens in conversion from what happens in post-processing.

    Good luck with it (ADL)... I still haven't seen the definitive answer as to what it does.

    Cheers,

    -Yamo-
     
  16. I don't have a D300 or D700, but I do have a D60 which has active D-lighting, but only at a single level (on or off). It does more than change the exposure; it does some processing before writing the NEF to memory, because it always brightens the shadows.
     
  17. Triggaaar

    Triggaaar

    Jun 15, 2008
    England
    Yes of course it does more than change the exposure, but most RAW procerssors won't be able to read what's been done, and if you use NX2, you can undo it all anyway - that's all except any exposure change, which is a permanant change to the raw file.
    Hi Yamo
    Yep - given the difference in descriptions, I wanted to do my own test (which is pretty easy).

    Well you can't really - if you're going to check your exposure, use compensation accordingly and work on the curves in post, you can do better than use ADL. But if not, the high setting will reduce the exposure by more than the low setting (assuming you have a large dynamic range in the shot). So although you can set high for all the photos you shot with ADL on low, that will only affect the curves, and not the original exposure. So while the high setting might not be for us, it could have a use for some.

    Are my details above not definitive :biggrin:
     
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