A Look at Aperture

A Look at Aperture

I have not posted any new entries in this blog since 2014 but in our current pandemic state it's time for me to get my mind on something else and give any possible readers an opportunity to do likewise.

Since I've titled this "A Look at Aperture" let's start by seeing what aperture looks like. The word aperture literally means "hole", an opening. In a camera the aperture is behind the lens and back in the days of manual lenses you could look through the lens and see the aperture and it would look something like one of the following.

When the lens is wide open (in this example labeled f/2.8) it is letting in all the light possible for that lens. When the lens is what we call "stopped down" it looks more like the image labeled f/22 and is letting in the least amount of light possible for this lens. Modern lenses stay wide open all the time except for the exact instant when the photo is taken which allows the image in your viewfinder on a DSLR to be as bright as possible when you are looking through it, but it prevents you from seeing what the aperture adjustments look like.

Now that we have all that out-of-the-way lets look at what happens to the image when you adjust that aperture. As I was sitting in my yard the other day, I looked up and saw the view below. I was looking through the limbs of a small Dogwood tree and seeing a large Oak in the background I got my camera and set it in the "A" mode (aperture preferred) which allows us to set any aperture we would like and then automatically adjusts the shutter speed to give us a good exposure. I set the aperture for f/22, that very small "hole" in the graphic above and got the first image.

Then sitting in the same spot I adjusted my aperture to it's largest opening which on the lens I was using is f/2.8 and look what happened. The small aperture had kept most of the image in focus so the close Dogwood and distant Oak both look quite sharp but the shot taken with the lens wide open, below created a very different effect. I was focused on the close Dogwood and the distant Oak is not in focus. Large apertures (which are the smaller numbers like 2.8) do not keep as much of the image in focus. What ever you have focused on (in this case the closer Dogwood) will be in focus, but anything closer or farther away will not be as sharp. In this case the smaller branches of the Oak blurred enough to disappear from the image while the trunk and larger branches are still visible but are not at all sharp.

This is the same effect photographers can take advantage of when shooting portraits. They will use a large aperture and focus on the eyes of the subject and the background (like the Oak tree) will be very unsharp which will cause their subject, still very sharp (like the Dogwood), to attract the viewers attention while making the blurry background seem unimportant and almost un-noticeable.

Your camera in it's fully automatic mode would most likely have given you the first image. There is nothing wrong with that photo but you could have created the second one if that's what you preferred. The difference is you can get what the camera gives you or what you would like. This is why so mucy time is spent in photo "how to" articles trying to get you out of the "automatic" mode. In this example I have used the "A" (aperture preferred) mode which is a semi-automatic mode which will get you a good exposure automatically, but allow you to pick the aperture that will create a look that you prefer.