Lens Aperture Explained – Exposure Triangle Pt.1

Okay, I’m not calling anyone a dummy here!  But you may feel like one when trying to understand your lens aperture and what it is.

And it’s the lens aperture, not camera aperture!  Each lens has its own aperture range, not the camera.

If I had a dime for every time I’ve explained what aperture is, I wouldn’t need to worry about putting my kids through college.  And that got me to thinking.  What if there were more people out there who just didn’t understand what a lens aperture was and how to use it properly?

I’m sure if you do a Google search on lens aperture, you’d get thousands of results, some of which would be absolutely no help to you.  (Okay, so a search of “lens aperture” resulted in 25.5 million pages!)

To begin with, the aperture of your lens is just one of three elements to the “Exposure Triangle”, which I will be covering in a future post.  But we need to break that down into it’s separate parts.

To put it very simply, your lens aperture is the “eye of the camera.”  But there’s more to it than that.

Why is it there?  What does it do?  How does it work?

If you’re anything like me, you want to know how everything about your camera works.  This will allow you to utilize all the benefits of your camera.

So, like I said, the aperture is like your eye, or more precisely your pupil.  When you go outside your pupils contract blocking out more light.  On the other hand, when you go indoors, your pupils must dilate to allow more light to enter your eye.

Now, the lens aperture isn’t automatic like your eyes.  You need to tell the lens, through your camera settings, to allow more light in or to block more light.

• “Stopping down” the aperture, or closing the opening, will block more light from entering the camera.  (Larger f/stop number.)
• “Stopping up” the aperture, or opening the aperture, will allow more light into the camera.  (Smaller f/stop number.)

There’s really no other way to put it.  If you need more light, choose a smaller number; if you need less light, choose a larger number.

(Can you tell that shutter speed is another element of the “Exposure Triangle”?)

But that’s not all folks.  Oh no!

Adjusting your aperture also determines your depth of field.  Oh great, you’re thinking?  How am I going to keep all this straight?

I’ve been given analogies from swimming pools to forests.  And all that did was confuse me more.

So I came up with a way to remember how the aperture affects depth of field on my own.

We all know that there the aperture is denoted by numbers, right?  For instance, you can have f/1.4, f/8, f/22, f/32, etc.  (By the way, aperture is also known as “F-Stop”)

Okay, so here’s the easiest way to remember this: The smaller the number, the less of your photo will be in focus.  The bigger the number, the more of your photo will be in focus.

That wasn’t hard, was it?

Now, if that’s all you want to know, quit reading now.  But if you want to know what your lens aperture is doing when you change the setting, read on.

This is where most people get confused.  When you choose a small number, your aperture actually opens up giving you a bigger opening.  And when you choose a larger number, your aperture closes down resulting in a smaller opening.

Wow!  Have I lost you yet?

One more time: Choosing a smaller number will open up your aperture.  Choosing a larger number will close down your aperture.

You may have noticed that when you want to get a nice landscape image and set your aperture to f/22, (because that’s what the manual told you to do!), your shutter speed slowed down.  This is because you closed the aperture, blocking more light from hitting the sensor.

If all you’re interested in is when to use what aperture, here’s a breakdown:

• More depth of field (Landscape images) = Large aperture number f/8, f/11, f/22, f/32, etc.
• Less depth of field (Bring more focus to your subject and blurring the background) = Small aperture number f/1.4, f/2.8, f/5.6, etc.

I hope I didn’t lose you too bad!  Aperture is one the hardest things to understand about not only digital photography, but photography in general.  So don’t feel bad if you’re a little fuzzy on the concept.

Hopefully, after reading this post, you understand a little more what aperture is and how it works.  Now it’s time for you to get out there and experiment!

Try different aperture settings and see what you come up with.

Next time: Shutter Speed, the second part to the Exposure Triangle.