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.
As part of our Photography Basics series we talked about Exposure already and this time we are going to cover the mystery of aperture. Aperture is probably the least understood setting of everything on your camera. While shutter settings are very easy to understand, to long of a shutter speed and you will get blurring, pretty simple stuff. Same with ISO, too high of ISO and you introduce digital noise. But learning how to use aperture properly can kill brain cells faster than a frat house kegger party.
A big stumbling block for many new camera users is how to figure out how much depth of field a particular image will have it in given the focal length of the lens, the aperture used and the distance to the subject. Trust me on this, trying to do the algebra to figure it out is not something most people want to try to do in their heads. In this article we will cover all of the math involved and then make it real easy with an Excel spreadsheet and some links to some free applications to help you out.