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Tuesday, 5 April 2011

Advanced Exposure

Your camera offers a range of advanced tools to assist and complement the built-in exposure meter
    In most situations your camera will produce perfect exposures but there are times where it may need a little help to get the best results. Fortunately most cameras offer a range of tools to help you judge and fine-tune the exposure that your camera has set. Here are a few of them.


    HistogramA histogram is a graph showing the spread of tones in an image, with the peaks to the left showing the darkest areas and the peaks on the right showing the brightest areas.
    In an average picture, with an equal number of dark and light areas, these peaks should be evenly distributed across the image. If your image is underexposed the peaks will be bunched to the left end, and perhaps fall off the end of the graph, while with overexposure they will be over to the right.
    Simply adjust your exposure to get the peaks nearer the centre. However, with some subjects the peaks need to be biased to one side. With a snow scene, for example, they should be over to the right. If they're in the centre it means your snow is mid-grey in tone. 
    Many cameras offer a live histogram so you can view it before shooting, rather than having to go into review mode and see it afterwards.


    Another sure way to guarantee perfect exposures is to shoot every picture at a range of exposure settings.
    You can do this manually, of course, but most cameras have an auto-bracket feature that can do this for you. When you press the shutter it will take one at the exposure it thinks is correct, plus one or more shots either side of that, in third, half or whole stop increments (determined by you). It all happens in a fraction of a second.
    Image: Bracketing is useful for tricky metering situations when you aren't sure which exposure will produce the best result

    Dynamic Range Adjustment

    A perfect exposure is generally regarded as one that records detail in both the darkest and lightest parts of the scene (excluding high- and low-key images).
    Sometimes, though, the subject contrast is beyond the sensor's ability to record detail in both the deep shadows and bright highlights.
    Many cameras now include a Dynamic Range feature that boosts detail in the shadows and/or holds back the highlights, much like Photoshop's Shadow/Highlight feature.
    Use caution, though. Apply too much and the image will look unreal, and noise will be increased in the shadows.
    Dynamic range
    Image: The Dynamic Range feature boosts shadow and/or highlight detail

    High Dynamic Range (HDR)

    High Dynamic Range photography, or HDR, takes the Dynamic Range adjust feature a stage further.
    It involves taking a range of shots at different exposure settings (you can use the auto-bracket for this), then using either Photoshop or dedicated HDR software to combine these shots into one image that incorporates a wider range of detail than you can get from a single shot.
    However, the effect can look cartoonish and unreal if applied too heavily. Some cameras now offer an HDR option in the camera.
    Image: HDR is a technique that involves taking several shots at different exposures and blending them together on the PC

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