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Using -exposure compensation to achieve higher shutter speed and low ISO

Discussion in 'Open Discussion' started by Lunatique, Dec 11, 2014.

  1. Lunatique

    Lunatique Mu-43 Regular

    97
    Sep 14, 2014
    Lincoln, CA
    One technique I've been using lately, is to purposely lower the exposure compensation while in aperture priority mode with auto ISO, in order to keep the ISO low and the shutter speed fast. With today's cameras having superior sensors than in the past, shooting a purposely darker photo and then raising the exposure during RAW processing still gets good results with just a little bit of noise removal. I think this is a more ideal approach than trying to get the "correct" exposure but being forced into a lower shutter speed and higher ISO, resulting in either a much noisier image or one with too much motion blur from the subject.

    Anyway, I just wanted to share that, for those who have never tried it. Those who also use this technique, do you have anything you want to share about this approach?
     
  2. 350duser

    350duser Mu-43 Veteran

    313
    Sep 26, 2012
    Brisbane, QLD
    Interesting and true. The teaching of expose to right and then recover highlights in post processing is now being replaced by exposing to left to get a sharp, non blurry image (thigns that we cannot fix in post) and recovering shadows in post.

    Use the same techinque at times myself.
     
  3. Replytoken

    Replytoken Mu-43 Hall of Famer

    May 7, 2012
    Puget Sound
    Ken
    I must admit that I am a bigger fan of ETTR and recovering highlights than I am of pulling details out of shadows and having to deal with noise. But different situations call for different approaches and we do what we have to to get the images we seek.

    --Ken
     
  4. Lunatique

    Lunatique Mu-43 Regular

    97
    Sep 14, 2014
    Lincoln, CA
    Yes, it's a case-by-case call we have to make. For a scene that's not too dark (such as a typical supermarket interior), dialing down the exposure compensation and raising the exposure in post-processing won't create nearly as much noise as if you were shooting an outdoor night scene or something similarly dark, such as a candle-lit dinner scene. There is a threshold to how much you can get away with. If it's a dark outdoor scene at night, of children running around in a darkly lit park or something, then you pretty much have no options left but to find a way to boost the lighting of the scene somehow.
     
  5. pake

    pake Mu-43 All-Pro

    Oct 14, 2010
    Finland
    Teemu
    I use this technique quite a lot - especially in poor light. My default setting is -0.3EV (-0.7EV on E-PM2) and I adjust it if needed.

    EDIT: Though I recently read that ETTR would be the better way of doing this but this only applies when there's enough light. I'm still trying to teach myself to do ETTR when it's bright enough...
     
  6. christofp

    christofp Mu-43 Regular

    135
    Jul 21, 2012
    I would say that underexposing and pulling the RAW is the same as rising the ISO. At the end, the current mFT cameras have very low read noise and the RAW picture quality is independont of ISO setting, only the exposure affects the result.

    I have a different approach but the results might be similar to yours:

    - When I have enough light, I do ETTR with EC = +1 or so. I use the blinkies. Sometimes, being lazy, I simply dial to ISO=low which gives nearly the same result.
    - In bad light or for action, I go to M mode, set the shuter speed and aperture as needed and let ISO=auto do the rest.

    In both cases, I will have a similar exposure as you.
    But with ISO=low I have ETTR without overexposed JPG-previews. And with ISO=auto I can avoid the underexposed previews too.

    Christof
     
    • Like Like x 2
  7. pake

    pake Mu-43 All-Pro

    Oct 14, 2010
    Finland
    Teemu
    Pekka Potka did some testing on this and came to the conclusion that the underexposing method seemed to maintain DR better. That's one reason why I choose to underexpose.

    EDIT: Tried to find the article on his website but couldn't...
     
  8. robbie36

    robbie36 Mu-43 All-Pro

    Sep 25, 2010
    Bangkok
    rob collins
    There are two very different concepts here.

    1) Is the Ops... The idea is that you take the very same exposure at 2 different ISO settings. Below is an example. The first is 1/25, f8 corectly exposing a shot at iso 12,800....

    ab_1_of_2_1.

    ...the second is the same exposure - 1/25th @ f8 - at iso 400. So 5 stops underexposed but increased 5 stops in post. There is very little difference.

    ab_2_of_2_1.

    This reflects the iso lossless nature of Sony sensors which is depicted in the chart below. The E-M1/E-M5 chart looks similar to the D800

    Clipboard_Image_10_1.

    2) Exposing to the right is all about getting the best image quality out of the lowest inherent iso. If you underexpose a shot 2 stops at iso 200 and then increase the exposure 2 stops in post all you are really doing is creating the shadows with a noise of a correctly exposed shot at iso 800.
     
  9. tosvus

    tosvus Mu-43 Top Veteran

    632
    Jan 4, 2014
    I'm actually a bit surprised the pictures are so different, as I always thought that some level of amplification is used both to control iso and exposure compensation. In my limited knowledge of how a digital camera works, I thought that once you have a set aperture (light the lens lets in) and a fixed shutter (amount of time the sensor is exposed to that light), all that is left is amplification. However, in your example, I prefer the high iso one as it does not have that green cast your second picture shows. Maybe it is the post processing causing it though?


    I think it is a good idea to often under expose a bit though, as recovering highlights are much harder than shadows, so the idea of using exposure compensation to some degree makes sense to me.
     
  10. BeyondTheLines

    BeyondTheLines Mu-43 Veteran

    262
    Sep 23, 2012
    Spain/USA
    Patrick
    Maybe you're thinking of one of the links in this similar thread? As you say, the conclusion was (at least on the Sony sensors) that once you get past ISO 400 you're better off underexposing and then pulling shadows in post due to more DR (as long as a higher shutter speed isn't needed of course).
     
    • Like Like x 2
  11. Lunatique

    Lunatique Mu-43 Regular

    97
    Sep 14, 2014
    Lincoln, CA
    That's interesting.

    I might have to try some tests of my own.

    For me, the only two reasons I'd expose darker on purpose are:

    1) Maintain lower ISO for cleaner image
    2) Keep a faster shutter speed to avoid subject motion blur

    If neither of those are really achieved any better by using a darker exposure and then raising it in RAW processing, then I might as well just use high ISO. I hope my testing proves otherwise, but if not, oh well. Another lesson learned. :)
     
  12. David A

    David A Mu-43 All-Pro

    Sep 30, 2011
    Brisbane, Australia
    Exposing to the right isn't about under-exposing, it's about over-exposing. If you expose to the right, you reduce the exposure in processing, not increase it. That means you get less noise in the shadows and that was Thomas Knoll's intent when he came up with the idea, but he also only recommended exposing to the right when the dynamic range of the scene was less than the dynamic range the sensor could capture and you could therefore safely over-expose a bit without clipping the highlights.

    The problem with this sort of discussion is that it's never very clear what would constitute a "correct" exposure. For my money the correct exposure is one which doesn't clip any highlights in which you want detail and/or tonality, and which gives you minimum noise. If you're shooting a landscape with a really wide range of luminance values in the scene and you want to retain extreme highlights like detail in sunlit clouds, then the correct exposure in my view is one that is going to have a lot of the scene apart from the sky looking under-exposed and you are going to have to raise exposure setting, possibly the shadows as well, and probably even lower highlights in your processing. On the other hand, if you have a scene with a smaller range of luminance values than your sensor can capture, then the correct exposure is probably going to look over-exposed and you're going to be reducing the exposure setting in processing.