One of the major contributors in how your photo is exposed lies on your lenses aperture setting. This is something that was briefly discussed in my Water In A Bucket Theory.
You may recognize this setting as it is characterized by a number you may have seen as you have experimented with your camera i.e. 2.8, 5.6, 14 etc
Essentially what it is is the size of the opening in your lens which light is allowed to pass through (and fall on your CCD or frame of film)
The wider the hole, the more light can pass through, and vice versa, the smaller the hole the less light can pass through.
Again, if you refer to the Water In a Bucket article, Aperture would represent the girth of the hose. If you also read the article you will know why this is important.
One thing that hasn’t been discussed is the possible effects that you have to consider when adjusting the lens aperture, particularly your DEPTH OF FIELD.
Think of your depth of field as a “zone”. It’s an imaginary zone that exists in front of your camera.
The zone has one main dimension: length
Anything that falls in this zone will be in focus.
Anything that falls outside of it, be it too close or too far, will be blurry (to varying degrees)
We refer to how long this zone is, as how DEEP it is.
Also we refer to the zone as a FIELD
How DEEP is the FIELD? Is a question the photographer asks themselves.
What is my Depth of Field?…
Here are some examples:
The depth of field (abbreviated as DOF) is very long. So long in fact EVERYTHING is in focus
The DOF is short. Just a few feet. Just enough for a child to fit in so they appear focused where everything else is blurred.
The DOF is very short. Actually just a sliver. It doesn’t even consume the entire subject.
There are apps that you can download (Search: Depth of field calculator) or if you really wanted you can calculate it yourself.
But if you’re like me you don’t have the time to figure out an exact number so I just follow the laws that govern depth of field
1) The wider your aperture. The lower the number – Light will pass through faster and vice versa. (Smaller aperture. Higher number. Light struggles to pass through)
2) The wider your aperture, the smaller your depth of field will be and vice versa.
3) The closer you are the smaller your depth of field will be and vice versa.
Because I mainly shoot guerilla style, I calculating as exact and ideal depth of field is very cumbersome. After a while as experience builds you can figure out what setting typically works best for your particular conditions (light, positioning, etc)
You can also opt to use your cameras APERTURE PRIORITY setting and simply set your aperture, and let the camera figure out all the other settings.
It’s all about experimentation, as it will lead to experience and knowledge.
Have fun shooting!!