One thing that seems to baffle a lot of new photographers is understanding the term “stop” as it pertains to a measurement of light. We see this word used over and over with regards to shutter speed, aperture, film speed, filters, lighting, and other ways that light is used. You may hear a phrase like “you should expose one side of face 1-2 stops under the lit side of the face and expose the background 1 stop under the main subject”. For many people that’s about like asking them to solve a complex calculus problem.

If you have ever shopped for a flash or read a review, you may have noticed a section of the spec called the guide number or GN. While this value is a measurement of power that the flash has and allows you to compare flash models, is this number useful to you at all? In this article we dig into the guide number and see how we can use this number help us dial in our flash and camera settings using some math instead of just guessing and retrying until you get what you want.

While today’s cameras do a pretty good job when in fully automatic mode, in order to make the most of your camera you should learn how to use your camera on the manual setting. To go full manual you will need to have an understanding of shutter speed, aperture settings, and ISO speed. In this article we will get you going and get you shooting like a pro.