Bracketing vs. Digital Exposure Compensation

Discussion in 'HDR Discussions' started by LokiZ, Oct 22, 2009.

  1. LokiZ

    LokiZ TPF Noob!

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    Is there a big difference between creating three shots using bracketing and creating three shots using Digital Exposure Compensation when creating HDR files for use with tone mapping process?

    I mean I know for one using DEC helps with the alignment problems but is there a down side?

    What are your opinions on this?

    Thanks.
     
  2. ann

    ann No longer a newbie, moving up!

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    i can't image why there would be a difference.

    the down side to bracketing with auto bracketing would be forgetting you had set the program and then it would continue to change exposures until you "null" out the program.
     
  3. Rmac

    Rmac TPF Noob!

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    Not that I'm an expert, but there really is no difference. The only time I bracket my shots is , for example moving clouds, the bracket mode will fire the shots faster. A lot of times I'm shooting more than three exposures, in that instance exposure compensation is the only way to go.

    Mac,
     
  4. Overread

    Overread has a hat around here somewhere Staff Member Supporting Member

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    It makes no difference and all the difference ;)

    Exposure compensation - first lets make sure we all understand what this mode is (not to beinsulting, but some people do get the wrong idea about how this mode functions). When you take a shot in any of the auto or semi auto modes the camera will look at the light in the scene, meter it using its own built in meter and then adjust the settings it has under its control (so for aperture priority it will adjust the shutter speed for example) until the settings will give a correct exposure with the light present.
    Now when you use the exposure compensation you tell the camera you don't want to do this - you want to over or underexpose what hte meter thinks is a correct exposure. You might do this because the lighting is very bright and might trick the meter into giving a fales reading (thus overexopsing the shot) or you might want to push a certain setting higher even at the cost of a little exposure (say your in aperture priority mode but you want the shutter speed as fast as you can - you might slip some underexposure compensation in - thus telling the camera to underexpose and thus it will use a faster shutter speed).

    Right so based on that when you use exposure compensation mode to bracket a shot or a series of shots you will get the camera giving you the setting it thinks are correct in the light present whilst taking into account the fact that you want to under/over expose the scene. The bonus here is it means you can select a different amount of over exposure compared to the amount of underexposure you use - so it might be avery dark scene with a few brighter patchs - so maybe one shot which is one stop underexposed (to get the bright patches) and then one shot two stops overexposed (to get the light and detail in the darker areas).

    Auto bracketing mode is just like using exposure compensation, save that the over and under exposure are going to be to the same amounts - so one stop, two stop, 1/3 stop etc... You will get the 3 shots - one "correctly exposed" one overexposed and one underexposed all taken in a series (though I belive for most canon cameras you have to press the shutter 3 times - once for each shot).

    You can also shift right into manual mode (since remember the camera is still only adjusting the 3 components of an exposure - ISO, shutter speed and aperture) if you want full control over the shots taken to be bracketed.
     
  5. musicaleCA

    musicaleCA TPF Noob!

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    Bleck. If you're doing HDR why fuss with all this? Just go to manual and figure it out from there. I mean, assuming you already have the exposure for the darkest shadow and brightest highlight, an semi-auto mode is just going to get in the way.
     
  6. LokiZ

    LokiZ TPF Noob!

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    Thanks for all the input. As far as my question... I was simply asking concerning the difference between the use of exposure compensation. I wanted to know how it relates to after the shot was taken use as compared to on camera use. It seems that the general consensus is that it makes no difference which is good to hear.

    Thanks everyone for your input. Overread, I especially thank you for the time you put into your reply.

    Just on a side note... sometimes I set my exposure compensation a little darker to gain a higher shutter speed when natural lighting is an issue. (as long as the frame is not too dark to begin with) Then I bump it back up in raw post. Just me I suppose.

    To me bracketing is just a preset to auto step through three exposure settings with out having to stop and change your setting manually between each shot.

    BTW my rebel (350) does not require the button be pushed for each of the bracketed shots if set to multi-shot.

    Thanks.
     
    Last edited: Oct 22, 2009
  7. musicaleCA

    musicaleCA TPF Noob!

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    Noooo, your question was definitely about HDR and tone mapping...

    Are you confusing exposure compensation (which is an on-camera function) with changing the exposure of the output RAW file in post? Because if you are, there's a huge difference.
     
  8. LokiZ

    LokiZ TPF Noob!

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    Musicale, that was my question yes it was for the use of HDR creation I agree (is why I posted here)... but the question was is there any difference between on camera exposure compensation and the raw exposure compensation you can do while "developing" you digital images from raw to what ever format you have chosen to output to.

    So the answer from you is there is a huge difference. I am all ears and eager so please go on.

    Thanks.
     
  9. musicaleCA

    musicaleCA TPF Noob!

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    Yes, there is a huge difference. Using exposure compensation on the camera adjusts compensation properly, by adjusting shutter speed or aperture (or both or ISO instead, whatever). The point here is that is still provides you with a properly exposed image.

    When you change the exposure of a RAW file, you're not adding any information nor dynamic range. This is why it's not useful for HDRI, because it doesn't produce an actual HDR image. In any case, the point is that you can't add information you didn't capture; when you increase the exposure of a RAW file, it just pushes the pixels of the image to high luminosities, and subsequently makes noise more noticeable (since noise is greater in the shadows, yadda yadda...I'm to sick to explain this clearly right now o_O). If you pull the image in the the other direction, eventually you're going to lose detail in the highlights.

    When you adjust exposure in the camera, it actually adjusts the exposure. (Hmm, that sounds odd, but it's true.)
     
  10. LokiZ

    LokiZ TPF Noob!

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    Thanks, I think you put it quite clear.
     
  11. ann

    ann No longer a newbie, moving up!

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    wow, i didn't understand the question and so there will be a difference, and as has been stated, doing that with one file is not HDR and not taking advantage of the process.

    sorry i may have mis-led you.
     

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