Hall - Digital Photography: Mastering Aperture, Shutter Speed, ISO and Exposure

While we all wish we could just pick up our cameras and start snapping beautiful images, taking truly great digital photographs requires a strong understanding of how your cameras exposure settings work. There are three main interacting elements that need to be taken into consideration when playing around with different types of exposures, and keep in mind that each aspect relates directly to light and how it enters and interacts with the camera.

These three important elements are:

• ISO - the measure of the light sensitivity of a digital camera

• Aperture the size of the opening in the lens when a photograph is taken

• Shutter speed the amount of time the shutter remains open

It is when we see these three elements work in conjunction with each other that we begin to understand how a photographs exposure is decided. It is important to keep in mind that even a small change to any one of these particular elements, will usually result in a specific and measurable impact on how the remaining two elements work to expose the film frame or image sensor.

While this isnt necessarily an issue, it is important to be conscious that it will ultimately alter the appearance of the final image in a significant and quantifiable way.

To those familiar with digital photography this explanation of how the three elements interact is a fairly clear one. For new photographers however, it often helps to illustrate the relationship of these three variables in the context of an analogy.

One popular and often mentioned example to explain exposure to those just starting out is the water bucket analogy. Put quite simply, try to imagine the way these three components work in conjunction with one another as a bucket being filled with water, with each element as listed below.

Desired exposure = a full bucket

The ISO = the size of the bucket

The lens aperture = the size of the garden hose

The shutter speed = the time it takes to fill the bucket

To elucidate the analogy further imagine that you are in a yard surrounded by buckets and garden hoses all of various sizes. Your goal here is to fill a bucket with water. You can opt for any size of bucket and/or garden hose that you wish.

Keep in mind that the size of the garden hose that you select will determine exactly how much time it will take to fill your entire bucket. Obviously the larger the garden hose, the faster your bucket is going to be filled. But what if you want to fill a bucket without using a larger garden hose, well then obviously youd have to opt for a smaller bucket. Makes perfect sense right?

In order to understand how this analogy directly relates to the often complicated exposure process that occurs every time you take a photograph, you need to think of your cameras digital sensor as if it were a bucket for collecting light. Large apertures will work to fill your sensor with light faster than a smaller aperture would.