ISO and the Exposure Triangle

In my quest for knowledge of photography one of the first things you learn is about the Exposure Triangle. This is where all those pictures you thought you took somehow vanished off of your memory card. Get it? Get it? I crack myself up.

But seriously folks, to get a properly exposed digital image you need three things to line up right. ISO setting, your F-Stop or appeture, and your shutter speed. I have a decent understanding of shutter speed and appeture, but ISO alludes me.  So for me it's the hardest point in this mysterious triangle.

Okay it doesn't allude me in the sense of I don't know what it does. From my understanding ISO is the sensitivity of, well, the sensor. Every digital camera has a sensor to record the image you are taking. This sensitivity affects how much light is able to be recorded on said sensor. The higher the ISO the less light is needed to record the image. This is particularly helpful when you are trying to take pictures of lions at the National Zoo and it's near feeding time. Which also happens to be dusk.


To get the proper exposure and to make sure everything is in focus I would need to have a shutter speed of at least 1/500 (to catch the lions moving and playing). However, I would also need to make sure the f stop is big enough to make sure everything is in focus, not just the lions head, but also the background or another lion. So I would need an f-stop of around f-8 or so. Well at dusk this doesn't allow much light onto the sensor, so would need to pump up the ISO. And that's where I run into trouble. How much is too much? Or not enough? Now my D3100 has an "okay" sensor on it. Not as nice as a new fancy D600 or even a pro level camera like the D3X. But as I don't have two grand laying around to drop on a new camera body then I'll be happy with what I have. My wife will be even happier that I haven't spent more money, and my back will be happy that I'm not sleeping on the couch.

Trial and error I'm sure is the answer, but when you can only get to the zoo twice a year it's a little tough to keep practicing. Especially when you get a little "buck fever" and want to get the images of the lions and tigers because they are just so darn cute with their rolling around and playing.

As you can see, these images are not the best, even with the wonders of post processing in Lightroom or Photoshop. I've been told ISO is the Wild West of photography. There are no hard and fast rules. I'm a hard and fast type of guy though....wait that sounded wrong. I mean I like rules. You set your f stop to X and shutter speed to Y and ISO to Z then you get awesome pictures of lions playing. People adore your skills and you get riches thrown at your feet. What's that? That doesn't happen? If it were that easy anybody could do it? Yea, yea, I know.

So I'm still learning the ins and outs of ISO and how it plays into the exposure triangle. And I'm sure 20 years from now I'll still be learning new things. But that's the point isn't it?