EV value ?

Discussion in 'Photography Beginners' Forum' started by Martin_Garcia, Nov 25, 2009.

  1. Martin_Garcia

    Martin_Garcia TPF Noob!

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    Hi all,
    I was reading this article Nikkor AF-S 50mm f/1.4G lens review diary | Cameralabs and I was confused when I read this: [...]The photo on the right was captured on this cold and grey December morning. Handheld at 1/45, f/1.4, 200 ISO, with -1EV compensation and the picture mode set to vivid.[...]. (There is a picture of a green door next to the text)

    EV ? ... Exposure compensation. Ok, how can you compensate the exposure?, changing the aperture, the shutter speed or the ISO. (can I say using a flash too ?) right ?. So the article is giving you the information of the aperture, shutter speed and ISO. Why would I need to now that he used a -1EV?. I mean, If I set the camera with those aperture, shutter speed and ISO values (in the Manual mode) will I have the same result?

    Thanks for the help.:D
     
  2. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    Welcome to the forum.

    Only if the light was exactly the same.

    When someone talks about exposure compensation, it means that they are adjusting the exposure away from the metered value.

    A camera's meter is calibrated to give you a mid toned exposure (18% grey). That won't always be the 'correct' exposure, and it certainly won't always be the exposure that you (the photographer) wants...so that's when we adjust the exposure away from --0-- on the meter.

    It could be in an auto mode, adjusting the Exposure Compensation....or it could be in Manual mode, setting an exposure that won't put the 'needle' on the --0--.

    Of course, when talking about the camera's meter...you have to consider what the camera is metering off of. You might get a different reading in Matrix mode than you would in spot or centre mode.
     
  3. Dwig

    Dwig TPF Noob!

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    As BigMike said, given the same subject and lighting conditions, yes.

    What the exposure data is saying is that the f/stop, shutter speed, and ISO are what was set and that these differ from the meter's opinion by -1 EV. What's not said is whether the camera was in an automatic mode and the -1 EV was accomplished by setting the camera's EV compensation or whether the camera was in manual and the exposure was adjusted so that the meter readout was at -1 instead of 0.
     
  4. Martin_Garcia

    Martin_Garcia TPF Noob!

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    Thank you guys.

    So If I understood, if you are in manual, the -/+ EV means you are over or under the 0 in the camera exposure meter. But if you are in automatic, the camera has a button or something to "adjust the exposure" where it will change some of those variables for you.

    Am I right ?

    Thanks again !
     
  5. ann

    ann No longer a newbie, moving up!

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    the button is called the exposure compensation dial and is that little square that has a plus /minus sign +/-. you can dial in the amount you wish to change.

    this is available on the program modes as they aperture and shutter options move together , think train cars; if you change the fstop the shutter speed also changes. with expsoure compensation it will make the change internally.

    with manul metering the users tends to that for themselves, as a lot of cameras will not allow the use of exposure compensation dial in the manual mode.

    There are some hand held meters that will read the options in EV numbers which are then translated into fstop/shutter options.
     
  6. Big Mike

    Big Mike I am Big, I am Mike Staff Member Supporting Member

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    As Ann mentioned, Exposure Compensation (or +/- EV) is something that is usually used in the auto modes. For example, if you set a +1, your images will be one stop above the meter reading for all the shots. You may take one shot, then turn around and be shooting something with very different light. The camera will adjust the shutter speed and aperture...but it will still give you an exposure that is one stop above the meter reading.
    So in simple terms...when shooting in an auto mode (including the priority modes)....you can use EC to adjust the exposure and pretty much ignore what the specific shutter speed and aperture values are. You are still relying on the camera's meter...but you are tweaking that exposure value a bit.

    When shooting in manual, the exposure values don't follow the camera's meter at all. But it's still viewable in the viewfinder. So for example, if you are in manual and you want a shot that is one stop brighter than 18% grey...you keep an eye on the meter while adjusting the controls, until the 'needle' is one stop above the --0--.
    The big difference comes when you turn around to shoot something else. In the auto modes, the camera settings would change (keeping the +1 EC)...but in manual mode, the setting won't change...so when the meter reads the new scene, you might be several stops away from the --0--.

    There are situations where is 'easier/better' to use the auto modes and situations where it's better to use manual. It's up to you to figure out what works best for you.
     
  7. Martin_Garcia

    Martin_Garcia TPF Noob!

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    Ok I got it. Thanks everybody.
    Personally I'm shooting everything in Manual, I think is the best way to learn.
     
  8. KmH

    KmH Helping photographers learn to fish Supporting Member

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    I don't know about Canon gear but Nikon is set up so that if you have compensation dialed in it biases the meter.

    If you have -1 EV of compensation set, when the meter is at 0 you really have -1 EV. If your not careful, you can be scratching your head trying to understand why your images are underexposed.
     
  9. ann

    ann No longer a newbie, moving up!

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    also, to add to keith's tip, with some cameras it is very easy to get into that mode and not even be aware. So be careful with random dialing and pushing "buttons"
     

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