Monday, December 27, 2010

Understanding exposure


So you have decided to take my advise and switch the camera from auto to manual mode, now what? Here is where it can start to seem a daunting task to beginners.  What do you set the camera to in order to get a well lit, useable image? Unfortunately the answer is not just a 'set it to such-and-such' and fire away. One needs to understand how a camera creates an image in the first place. While I will give you a short introduction in this post I highly recommend reading more about exposure for a fuller understanding of picture taking.

Anyone who is serious about learning photography is bound to head off to the library or book sellers to pick up a few books about photography. After all, if you want to learn from the pros the fastest way to get to them is through their publications. But which pro to learn from and which book to buy? That is determined by what type of photography you are looking to pursue. Find the artist you like then do some research and see if they've published anything. but I digress.

At this point there is only one book you should really have in your library and that is "Understanding Exposure, 3rd Edition: How to Shoot Great Photographs with Any Camera" by Bryan Peterson. He explains the process of attaining proper exposure in an easy to digest format.

In the book Mr. Peterson explains the 'exposure triangle'. This triangle consists of shutter speed, aperture and ISO. By controlling one or more of these settings you will be able to adjust your camera to capture a perfect exposure. While this description is over simplistic, keeping this principal in mind will form the foundation to all subsequent lessons.

For now let us just concentrate on the very basics. While you will be shooting in manual mode you will notice that your camera's metering system is still active. Without getting into all the technical stuff right away, by making adjustments to any of the three elements in the triangle you should be able to adjust your camera so that the meter indicates a correct exposure.

Begin by adjusting your ISO setting first. This is often the easiest and least worrisome of the three settings. ISO references your camera's sensitivity to light. The higher the number the more sensitive the photo receptors are to light. So in bright outdoor light an ISO of 100 or 200 can be used. For indoor shooting and ISO of 400 is more than adequate. In lower light situations higher ISO setting will need to be set. For the most part, once you have set your ISO for a particular type of light you don't need to mess with it again.

The other two settings, shutter speed and aperture, are trickier. Aperture refers to the amount of light entering the lens while shutter speed is the amount of time the shutter remains open to the light. Lets talk about aperture first. Keep in mind that understanding the numbers associated with aperture is a bit dyslexic. The smaller the number the larger the lens opening. This also translates to -- the smaller the number the less background that is in focus.

Depending on your subject matter and how much background you want in your image will determine the aperture setting. As a rule, a setting of 8.0 to 11.0 will give you a reliably good image without too much concern about background. Realize that the smaller the aperture (larger number) the slower your shutter speed will need to be.

So now we have established ISO and aperture. ISO to light sensitivity and aperture to the amount of light entering the lens. The final piece of the puzzle is shutter speed. Here is where your camera's light meter will come into play. While looking through your camera's viewfinder, adjust the shutter speed until the camera's meter is centered, indicating a proper exposure setting. Fire away and take a picture and look at it on your camera's preview screen. If it is too dark simple slow your shutter speed down. If it is too light, speed it up.

Keep in mind that the above description is simplistic in advanced shooting techniques not the most ideal description. However, it is designed to give the beginner a starting point to build upon.

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