This is Part 2 in our series on taking better digital pictures. Part 1 dealt with achieving proper focus. This installment will deal with exposure issues.Exposure determines the amount of incoming light that reaches the image sensor. Your camera controls exposure by varying the lens opening (aperture) and the amount of time given to take the picture (shutter speed). Understanding these two concepts - and how they work together - will give you interesting and unique digital pictures.
Aperture
The term aperture refers to the physical part of the camera that is the circular window that opens and closes when you press the shutter. It also describes the size of the window opening. This opening size is called the f-stop. The smaller the f number, the wider the aperture opening.
Wide apertures (low f numbers) result in limited depth of focus. Therefore the background will tend to blur. This may be the effect you want. If you want the background to be in focus along with the foreground subject, you will want a higher f number.
Shutter Speed
Cameras use a shutter to control the duration of exposure. This time is usually a fraction of a second. Shutter speeds do more that just control the amount of incoming light. A fast shutter speed tends to freeze motion. A slower shutter speed tends to exaggerate motion.
Aperture + Shutter = Creativity
In portrait photos, a combination of open aperture and fast shutter speed will blur the background (short depth of field) and throw more attention on the subject. Notice however the depth of field in this TGIF Kimberly picture. The shutter was set to use a rather narrow aperture which kept the background somewhat more in focus. Check out these pictures on Vazaar for some interesting play with aperature and shutter...
ISO Sensitivity
Just to mix things up a bit more, digital cameras also offer some manual ISO settings. In older film camera terms, this was a film rating about how fast a film was. In your digital camera, you can manually set ISO sensitivity to achieve increased brightness - at a cost of some added picture noise. Experiment with different settings for aperture, shutter speed and ISO all at once add real creativity to your pictures.
Remember - you can shoot hundreds of pictures with no film cost!!
Your camera's auto exposure setting will adjust all of these for you automatically - and that's convenient for some quick snapshots. Special scene modes will set adjustments according to common shooting scenarios. In the next part in the series, we will discuss various scene modes and how they work to optimize your pictures.
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