The Exposure Triangle – 31 Days To Better Photography

By
Peter West Carey
– March 1, 2011Posted in: 31 Days To Better Photography, Featured, Photo of the Day, Photography

First, there is The Exposure Triangle. It balances all things. Makes things right in the Universe. Or maybe it is just a handy metaphor.

To be honest, the Exposure Triangle, to me, is better explained as two Teeter-Totters, which isn’t nearly as sexy as a triangle. What the Exposure Triangle is trying to tell you, is there are three things which have an impact on proper exposure of an image on film or on a camera sensor:

We’ll be going over each of those in more detail in the following days, so for now let me make this hopefully short and to the point.

Shutter Speed – This, essentially, how fast your camera blinks. Remember the days of film and how you were never, ever, ever, ever supposed to open the back of the camera while the film was loaded? That’s because film is set to react to light and if you don’t control how much light hits it, it freaks out and exposes EVERYTHING. There’s no need for a triangle at that point. And at the time, there was usually only a need for cursing because too much light killed that roll of film. So the shutter does the blinking of the camera. Everything is dark inside the camera and then “BLINK”, the shutter lets in how ever much light it is told to. More on this tomorrow.

Aperture – Aperture is a bit harder to understand so let’s use an analogy.  Picture an enclosed room. Make it solid and maybe place yourself on the dark side of one of the walls. Not Darth Vader dark side, or Pink Floyd Dark Side, just pitch black inside. Are you with me? On the other side of one of the walls is very bright light and a 40 ton, 8′ wide wrecking ball. Ball swings and BAM!!! 8′ wide hole in your wall. How much light do you think is coming in right now? Tons.  Now back up and let’s do this again. Instead of a wrecking ball, let’s use a 1” wide drill bit. POP! Hole is in and, if you are standing back 10′, how brightly lit is the room now? Can you see now how Aperture affects how much light comes into the room? More on how the aperture does other cool stuff on Thursday.

ISO – People often ask what ISO stands for. International Standards Organization. I get blank looks after that answer or knowing, “Oh, ok” looks followed by, “Huh?”. Wikipedia has thousands of words on ISO as it relates to photography, but in short, we’re talking about sensitivity here. It’s the exact same sensitivity as if I punch you. If you’re a body builder, you’re not that sensitive to a punch. But if you’re….oh jeeze, now I need to come up with an example where I punch something sensitive…a cute, fluffy bunny. Sorry bunnies. Chances are, with the same punch the bunnies would yelp and jump a mile because of the guns I’m packing on this 6’1” frame. (sorry, obscure pop culture internet references may come up this month)

Better yet, let’s go back to the wrecking ball analogy. You’re in the pitch black room before the ball smashes an 8′ hole in the wall. If you’ve been in the pitch black room for an hour, your eyes are far more sensitive to light, aren’t they? Big old open pupils trying to gather as much light as they can. BAM! Hole in wall and ARGGHHH!! You sensitive eyes don’t like all that light.
Same scenario but this time, before the ball strikes, we’ve been holding a flashlight pointed into your eyes for 10 minutes. By ‘we’ I mean me and the bunny you made me punch. Your eyes are now constricted and not so sensitive, are they? BAM! Hole in the wall and you think, “Eh, not so bright”. Your eyes were less sensitive.
ISO will be covered on Friday.

Got all that? Shutter speed = how long light hits camera sensor. Aperture = how wide is the hole letting in light. ISO = how sensitive the sensor is to light.

Here’s where the triangle comes in. Visualize it like this:

Except for the bunny, it’s a nice balanced triangle. However, the moment one of those corners changes, let’s say you change the ISO from 100 to 400, then the triangle gets all fuddled up and is not in balance any more. If one, or both, of the other variables aren’t moved as well, the bunny picture won’t come out properly exposed. And by properly exposed I’m talking about an ideal here. After you learn the rules through these 31 days, you’re welcome to break them. But until then, we’re shooting for properly exposed images.

Another way to think of it is:

With the Exposure Teeter Totters Of Doom, if ISO wants to move up or down, one of his buddies (or possibly both) needs to go in the opposite direction to make all things even. This is all in regards to the amount of light hitting the camera sensor. Any of the three could be in the middle and if it is changed, one or both of the other two needs to change to keep exposure proper and level.

That’s it!! That’s the Exposure Triangle. It’s not a huge mystery, really. It is simply an attempt to keep all things in balance for a proper exposure. Those three things, explained more fully over the coming days, are what determine a proper exposure. ISO, Shutter Speed and Aperture.

Questions?  And please realize, as this is only day 1, I may defer some of your answers to another day, especially as we are covering a lot of ground this month.

Experiment With It

Here are a few practical experiments you can try at home to help the concepts take form:

With The Exposure Triangle concept firmly in mind, it’s time to understand how your camera captures light for Day 2.

31 Days To Better Photography is a series written by professional photographer Peter West Carey on The Carey Adventures.Com. The series is designed to unravel the mysteries of photography so you can take better pictures. Subscribe here to receive all the updates, and bonus material. Your comments are always welcome.

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