There are three ways to change your exposure: change your f-stop, your shutter speed, or the ISO. Fortunately, each of them is based on a twice as bright, twice as dark incremental scale. Unfortunately, it's STILL confusing.

Yesterday’s lesson about ISO and today’s lesson are admittedly a bit technical. Every once in a while it will be good for us if we dive into the cold water and swim a lap or two; I promise not to make a steady diet out of it. But these litle bits of knowledge can take you a long way toward using your camera on manual settings and manual settings is where the creative stuff happens. Please don’t be afraid. I’m here to help.

What I want you to get out of today’s lesson is actually very simple. If you get it, then you can go outside and play.

This is it:

There are three ways to adjust your exposure. They’re f-stops, shutter speeds, and ISO.

That’s all I want you to get today.

You need to watch the video. It’s really helpful to have visual aids when you’re discussing this relationship. Here are a few things to keep in mind:

The numbers on shutter speeds make sense. 1/30th means a thirtieth-of-a-second.1/125th one-hundred-and-twenty-fifth-of-a-second.

The numbers on f-stops and ISO make NO sense. They are just some numbers somebody somewhere slapped onto them and have been annoying photographers for decades. The f-stop numbers f2.8, f5.6, and f8 mean almost nothing to me. I mean, give me a break! Do we have to have f-stop numbers with decimal points in them? And the same with ISO; ISO 200, ISO 400, ISO 1600 are just numbers to me.

One day, I’m going to make a video using the patented Nick Kelsh Exposure Slide Rule you see in the video to show you how the three scales— f-stops, shutter speeds, and ISO— affect your photographs. That’s going to be more fun.

But just for now, today, all I want you to get is this:

F-stops, shutter speeds, and ISO are all built on a sliding scale where every increment is twice as bright or twice as dark as the increment next to it.

And if you don’t get it, don’t worry, I’m coming back to it.

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