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Friday, 25 January 2013

How to Understand the Histogram on Your Camera


One of the great aspects of DSLRs is the histogram feature that can be set to appear each time you take a photograph. Most people either do not know about this feature, or do not understand what the information presented means, but for one who does know, it can present very useful knowledge as to how your photo has been taken.
If you know how to read a histogram, you will instantly be able to know whether the image you have has been under exposed, over exposed or is at the correct exposure.
The first thing you should do is to set your camera up to display the histogram. The way you do this varies on camera to camera, so if you don't know how to set it, refer to your user manual. It'll quickly tell you how.
Once you have the histogram set, you're ready to go, so go ahead and take a photo. Look at the photo and then look at the histogram displayed. For a perfectly exposed image, you should generally have a spiked graph with the majority of the information in the middle and tapering out towards the sides.
No two histograms will look alike, but generally, if your histogram is similar to described, it means all the information has been captured and your image should be good.
The set up of the histogram has the first third dedicated to dark tones, the center third to mid tones, and the right side to high tones.
If your image is under exposed, then the majority of your graph will tend towards the left of the graph. Furthermore, it will appear that the start of the graph does not begin at zero on the y axis (the vertical axis), and this means that not all the information in the image has been captured. This is known as clipping, and means your dark areas are far too dark for your camera to pick up the information.
Therefore you should recompose and consider increasing the aperture, the ISO slowing your shutter speed down.
Similarly, if your graph tends towards the right, then you have overexposed, and you have a lot of pure white in your image. Again, clipping will occur if on the y axis, the graph does not start at zero. So you should recompose the image, decrease shutter speed, ISO or reduce the aperture size so not so much light is coming in.
While the histogram is not perfect, it can give you a really good indication of how your image is, and enable you to understand if you need to reshoot. Your LCD preview will give you an idea of how your image came out, but the histogram tells you more precisely any potential problems.
Once you get used to the histogram and the information it displays, you'll quickly be able to correct on the spot any exposure problems you have and reshoot instantly.
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