How Your Flash Works. An Important Cheat Sheet for Photographers

If you’ve ever been curious about how your flash works, then check this out.

You already know apertures change the depth of field. Of course, they also affect light gathering. But when using a flash, the entire game changes. Lots of photographers have no idea how their flash works, so they get discouraged and give up. But we’re going to share a visual guide that you can use whenever you wish. If you’re just learning flash, we recommend bookmarking this page and checking out more of our cheat sheets. Head on past the jump, and let’s explore.

This infographic is shamelessly being borrowed from Useful Photography Tip #52. You can check out all of our Useful Photography Tips. We’re just adapting it to the infographic/cheat sheet format. So let’s dive in. First, you need to understand the following things:

• Your camera has a flash sync speed. This is the maximum shutter speed a flash can sync to.
• Shutter speeds only affect the ambient light.
• Your f stop affects the effect of the flash output. If the light is set to a manual 1/32nd, then a narrower aperture will take in less light.
• If you want a shallower depth of field, open the aperture and lower the power output from the flash.
• If you want a deeper depth of field, close the aperture and crank up the power output from the flash.
• ISO controls overall sensitivity.

In this situation, we’re shooting a macro image. The light is so much larger in comparison to the subject. According to the laws of physics, that means the light will be softer. To make it even softer still, you can use the wide-angle diffuser. Alternatively, you can also put it in an umbrella, softbox, etc., but that could end up being too soft. You’ll need to raise the ISO and overall sensitivity in that case, which makes it a delicate balancing game. You also need to get a better understanding of what you want in the image. Don’t lose sight of that.

This works for more than just macro photography, by the way. The science and physics behind how your flash works adhere to studio strobes too.

Take a look at the infographic, and we’ll continue about TTL flash afterward.

TTL flash is a much different beast. According to our previous post on how TTL metering works:

“When you connect a TTL capable flash to your camera’s hot shoe (or via radio or something else) the flash essentially looks at your camera’s aperture, ISO and the distance away from your camera the subject is (in some cases) and adjusts accordingly.

That’s it.”

Over the years, TTL has become more complicated. Each camera system has its own matrix metering system, so they’ll expose images in different ways. It’s very odd. But that gets incorporated into their flash system. Theoretically, f2.8, ISO 400, and 1/125th with TTL flash output should give you the same results no matter what system you’re using, but they each expose differently. The Profoto system works much differently from Canon or Phottix or Godox. So you just have to do with them and realize that they’re each their own beasts.

This is one of the biggest reasons why photographers prefer manual flash. Because, like their camera, they can tell the flash to do precisely what they want it to do. With TTL, it’s doing what it thinks you want.

The Phoblographer’s infographics are made with VisMe.