EV adjustment for digital- what do the values mean?

Discussion in 'Mirrorless Digital Cameras' started by bob_morris, Mar 26, 2008.

  1. My Cintar digital camera was put out on the market in a rush, when they came
    out, & little thought to the operators manual. It has 9 settings for EV from
    +2.0 to -2.0,,,,,,which is the lighter & which is the darker exposure. Now I
    use it on 0 to be safe. Example: sunlight--2? cloudy +2?
    Thanks. Bob RMo8235376@aol.com
  2. +2 and -2 (and values in between) are called Exposure Compensation. They are there for you to tell the camera that for a particular scene you want it either brighter (zero to +2) or darker (zero to -2) than what the camera /thinks/ it should be.

    This has nothing to do with being outside or inside or cloudy or sunny. It's just an available option for you to override what the camera thinks your exposure should be.
  3. My Nikon has EV adjustment, too. It is an exposure control used to override the automatic exposure calculations the camera makes for itself. The guys that wrote your UM must have gotten the job after they were laid off having finished writing mine! At first I thought that EV and f-stop were the same thing. Then I paid more attention to the settings stored with the images and came to see that a more constructive interpretation is to say that a change in EV has the *effect* of a similar change in f-stop. The user (of my fully automatic camera) cannot control the exact part of the exposure the camera will adjust. It can be any of the f-stop, shutter speed or ISO.

    I do adjust the EV for some things. My camera is more sensitive to magenta than to other colors, and so routinely overexposes things like red roses and the like. I have learned to see the milky loss of highlight detail for what it is in the LCD and pull back the exposure with the EV control. I repair the overall underexposed image in post-processing. Other than this, I have not had to change EV very much.
  4. - makes it darker, + makes it lighter. try this. Take a picture at 0, if it looks too light, subtract light by using - EV compensation. If it's too dark, add light using the + EV compensation. It's all quite ingenious.

    The auto exposure on good cameras will need little adjustment. The EV compensation is when you want to override the computer's presets as to what should be properly exposed.
  5. Your camera has an in-camera meter. It measures the reflected light from the subject and the scene. But what does that mean?
    Reflective meters are usually calibrated to something called middle-gray, an about 13-18% gray tone. Simplified, if you shoot a picture, the scene's brightness will be measured and automatic exposure will be adjusted for a middle-gray tone.
    Depending on your subject, this may or may not often be the "correct" value. A photo of a white cat on white linen or a black dog in a coal mine will not be rendered accurately if you depend on the default setting (±0). So the photographer has the task of evaluating the framed scene and use his experience to dial in the best exposure compensation. Fair skin is brighter than middle-gray, so I have to overexpose a little when shooting tight portraits. Backlighted scenes, black clothing or dark skin must also be compensated for.
    So, this means you do not generally set specific EV adjustment for a particular lighting, but for how a scene looks or what kind of aesthetic you want to archieve.
  6. To add a little, 'in practice' I will use +1/3 EV or more for portraits to achieve more of the high key look when I'm shooting in Aperture Priority mode.
  7. Another point: Look at the histogram for a shot. If it crowds the (b)right end, turn down the exposure compensation a bit (towards the negative) to keep from overexposing. If the histogram is to far from the right end, turn up the exposure compensation to keep from underexposing. Each EV unit represents a doubling/halving of exposure time or an addition/subtraction of one aperture value.

    About high-key shots: They can be done with post-processing (e.g. in PhotoShop). Personally, I feel it's best not to overexpose. You can do whatever you want later on, after it's in the computer. In fact in some circumstances, it's best to underexpose by perhaps a stop (1 EV value). For instance, if there's a bright blue sky, exposing it to its maximum value will wash out the sky and make it white. If you have a color histogram, simply avoid clipping any of the colors.

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