How Much Light Do I Need – Understanding The Light Meter
In the last article, I discussed the two primary camera controls: shutter speed and aperture. Both impact the amount of light reaching the digital sensor (or film for those still using traditional cameras). The key question, or course, is how much light do you need to take a picture?
The good news is that cameras are designed to help you determine the correct amount of light. In fact, the auto exposure mode only requires you to point the camera in the right direction and press the button. It does everything else for you. Lets pretend for a minute, however, that you are a control freak and feel the need to select your own shutter speed and aperture. In that case, you will want to set the camera to manual exposure, thereby taking control of both the shutter speed and the aperture settings.
Once the camera is set to manual exposure, you need to locate the exposure meter. An exposure meter generally consists of a small line with values ranging from -2 to +2 and can usually be seen when looking through the camera’s viewfinder (look through the eyepiece like you are taking a picture). It might also be visible on one of the LCD screens (each camera is different).
Now that you have located the exposure meter, lets talk about how to change the amount of light. Pressing the shutter button part way should activate the exposure meter, causing a small marker to appear somewhere along the line. Changing either the shutter speed or the aperture setting will cause this marker to shift positions along the line. Changing either the shutter speed or aperture to let in more light will move the marker towards the positive side of the meter. Reducing the amount of light will move the marker towards the negative side of the meter.
So, what setting do you need to have the correct amount of light? 90% of the time the correct answer is “0”. Shooting when the exposure meter has a positive value results in the image being too bright (overexposed). Shooting with a negative meter reading produces an image that is not bright enough (underexposed). Using an exposure meter reading of “0”, however, will produce a well exposed picture. Give it a try.
Now, before seasoned photographers start to point out the limitations of what I have just said, let me point out that the above method is a simplified way to quickly determine proper exposure using manual camera controls and it will work well about 90% of the time. The other 10% of the time, however, it fails miserably. Unfortunately, the failures usually occur during the most dramatic lighting conditions that result in the best images. Also, this method does not address the creative impact shutter speed and aperture settings have on the photographic process. Having said that, don’t get overwhelmed. All exposure begins with the light meter. Once you understand how to manipulate that, everything else will fall into place. Oh, did I mention that I will be talking about those exceptions in upcoming articles?
