Picking a mode to shoot in: Aperture Priority

Now that you’ve skimmed though the basics and either thought, “I already know all this” or “what the ?!” (Don’t worry I had to re-read my notes many times before it all starting making sense). Let’s start with my favorite mode to shoot in. I love a shallow depth of field. So, most often I shoot in A mode (aperture priority). This means I choose the aperture and the camera auto selects shutter speed and ISO.

A few things that will help achieve a good blurred background (shallow depth of field):
1. A low f-stop number. The lower the number the bigger the lens opening and the more quickly things fall out of focus
2. Have some distance between your subject and the background
3. Fill the frame with the subject

For simplicity we will start with a stationary subject. (More on moving subjects at a later time)
I am going to put my camera in A mode, change the aperture to f-2 (I am shooting with my 50mm f/2 lens, so this is considered shooting “wide open” the lowest f/stop available for this lens). I’m shooting outside so there is plenty of light - the shutter can move fast and the ISO can remain low.

To demonstrate #1 above (the f/stop number) I will try taking a photo of a rasin box at different apertures.
At f/2 the background is nicely blurred, the depth of field is very shallow:

At f/16 much more of the background is in focus:

To demonstrate #2 (getting distance between the subject and the background) I’ve placed the rasin box in front of a fence.

Here the box is only about 6 inches from the fence. Aperture is f/2.

Here the rasin box is about 1 foot from the fence, aperture still f/2.

To demonstrate #3 above (filling the frame with the subject) I will leave the rasin box about a foot from the fence.
Take a look at the photo above where the box is 1 ft from the fence, notice how blurred the background is. Now, I step back a bit and take a photo of the rasin box.

See the difference in the background?

Just to tie it all together, as I am increasing the f/stop #, which decreases the opening in the lens, what is happening? Less light is coming in. So how does the camera compensate? The camera decreases shutter speed to allow longer exposure, or the camera will up the ISO to increase sensitivity to the light that does come in. So you can trouble shoot here if you find you changed your f/stop number and now you shutter is only going at 1/80th of a second and you want to stop motion (need a speed of 1/150), try upping your ISO to 200, 400 and see how the shutter speed changes.

So there is your start to controlling depth of field!


Upcoming:
Picking a mode to shoot in: Shutter Priority
Finding Focus
Why is my photo blurry?
White Balance
Spot Metering