Depth of Field

Usually I like to start you off by talking about the settings of your camera. No matter what your camera is, these days, you'll most likely all have the same settings. P, A (or Av), S, M. Program, Aperture, Shutter, Manual. Let's get a basic overview of each. 

Program basically means your camera is going to choose both your shutter speed and aperture to get the correct exposure for the particular photo you are taking. 

Now, let's back up a bit first. The definition for exposure is this: In photography, exposure is the total amount of light allowed to fall on the photographic medium (photographic film or image sensor) during the process of taking a photograph. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance over a specified area.

Now you are saying, 'Jay, what the hell does THAT mean?' Basically all it means is that your camera sees an amount of light. The camera then determines how fast or slow the shutter needs to open for that light to get into the camera to 'make' that photo. That "amount" of light let into the camera depending on the shutter speed is determined by the aperture. 

The Aperture, which is made up of those numbers like: 2.8, 4, 5.6, 11, 16, 22, allows a certain amount of light into the camera. That's what we'll deal with in this post. 

Each aperture number has a correlating  shutter speed number depending on how much light is available. The aperture has set parameters. This will be noted in your manual but for this example we'll say that our camera goes from 2.8 to 22. When you are shooting in Aperture mode, you cannot go outside of these boundaries. This is NOT the case in Manual setting. You may be shooting with the aperture "wide open" (2.8) and the camera is still telling you that your photo will be underexposed, that there is not enough light coming in to get a correctly exposed photo. 

Here are some basics to follow and keep in your head:  

The lower the number (2.8) the more light the camera allows in. The higher the number (22) the less amount of light. Think of the aperture as the pupil in your eye. When it's dark out, your pupil gets larger. When it's bright out, your pupil gets smaller. So, in Program (Auto) mode, your camera makes this decision for you. 

But have you ever been taking photos of someone and you want that person to be the focus of your photo? But when you shoot in Auto mode, the camera keeps everything in the back of that person in focus. And you notice there is a lot going on in the background to detract your eye from your true subject. This is where switching the camera to Av (Aperture) Mode comes in very handy. 

Here is a simple rule: The lower the number (2.8, 4) the less the background will be in focus. It will look 'blurry' in the background. 

The higher the number (16, 22) the more in focus your foreground and background will be. You'll have more 'depth' in the photograph. 

You'll see this example in both photographs as examples. In the first photo, I wanted to convey the vastness of the Everglades and put the Great Blue Heron into perspective with it's landscape. So I wanted more of the photo to be in focus. In the second photo I don't really care about the background. My focus of the shot is of the Elk. Nothing in the background is interesting to me.

 

There are a couple of things you should know. It's not that simple. Distance to your subject can greatly affect your depth of field. You'll notice this in Macro (or close-up) photography mostly. Also, you have to be aware of the amount of light you are working with. 

Practice shooting a subject in aperture mode in all the different apertures. Notice that the shutter speed is also changing when you do this. This information will come in handy when we discuss shutter priority and you want to learn how to get that 'cotton candy' look from water or you want to know why everything is so blurry when you shoot indoors with no flash. 

Your camera may look something like this inside: 

2.8    1000  = 1/1000 of a second

4        750

5.6     500

8        250

11       125

16       90

18       60

22       25

Keep in mind that hand holding your camera below 60 (1/60th of a second) may cause you to have a blurry photo. 

Enjoy and happy shooting, 

JB

Please feel free to contact me with any questions you may have. Shoot first, ask questions later!