Keep in mind, however, that the bigger the flashgun, the heavier it is going to be. Flashguns are weighty pieces of camera equipment. So, if you’re planning on hiking all day with it, you may look into a lighter, less powerful flashgun if you don’t want to add the extra weight to your backpack. When looking at the GN number, you also need to be aware of whether it is in feet of meters. There is a huge difference between the two, and you want to make sure that you’re comparing the right thing.
Another thing to consider is how technical you are. Your standard flash is going to illuminate things in front of you, but it can tend to look less natural and could cause red eye in your photos. A flashgun will eliminate most of this, but with something of a cost. There are a lot of extra features that you’ll need to figure out when you buy a flashgun.
But, you also need to know something about cameras to use these features. If you buy one with all the bells and whistles, practice with it first. Once you get comfortable with it, the external flashgun will come in handy. Luckily, most people will only be using the standard features
Most external flashguns should come with their own power source, typically AA batteries. Just in case it doesn’t though, be sure that the one that you are looking at does. If not, you’ll be pulling power from your camera, which could cause your batteries to die sooner.
You should also consider how far away you’re going to want to illuminate objects. If you’re planning on taking photographs of something that is 20 to 30 feet away, you should consider buying a flashgun with a zoom feature. That way, you can zoom into the area of the subject that you want to light up with the flash and frame it up, significantly increasing the power of the flashgun.
If you’re planning on just taking portraits, you may want to buy a flashgun that can be fitted with a lighting stand. Here you can put your stand where you would like to use it. These units will not be as strong as your typical studio flash unit.
One thing to remember with flashguns is that digital SLRs manufacturers have flashguns designed specifically for their cameras. These flashguns won’t fit another manufacturer’s camera. With that said, you can probably find some third-party flashguns that will work with your camera. Just make sure that it's compatible with your camera before you purchase it.