Today I'm going to jump into the world of off-camera flash. If you haven't yet mastered on-camera flash, it's a good idea to do so before trying to add a second flash. Click here to learn some of the basics of flash first.

While OCF does add a bit of complexity to your set-up, it's WELL worth it. Check out some of these amazing images you can produce just by including one off-camera flash into your set-up:
When I started to use OCF four years ago, my enjoyment of receptions sky-rocketed. I used to be so bored with my reception images. But now I feel like I can produce something that is in keeping with the quality of the rest of the images I take throughout the course of a wedding day.

Today I'm going to talk a bit about the different components that work together to create your exposure when using OCF.

When shooting with natural light, there are three variables you adjust in order to come up with your exposure: ISO, aperture and shutter speed. When using off-camera flash there are five: ISO, aperture, shutter speed, flash power and flash-to-subject distance. I'm going to briefly discuss each of these variables and how they impact your exposure when using OCF.

Shutter Speed
Shutter speed does NOT impact your flash exposure. It only impacts the exposure of the ambient light in the image. So you can change your shutter speed and it will have no impact on the exposure of the subject if your flash is your main light. When using OCF, you have a limitation called "sync speed" wherein you cannot use a shutter speed faster than 1/200 (Canon) or 1/250 (Nikon) of a second or you will get dark banding in your images. The sync speed generally is not an issue when shooting receptions because you don't need to go near 1/200 of a second.

Aperture does impact flash exposure and it functions exactly like it does when shooting in natural light. If you open up your aperture, you allow more light into the exposure; if you close down you let less light in.

Flash Power
When using OCF, set your off-camera speedlight mode to M for manual. (Keep your on-camera speedlight set to ETTL) You can then adjust your flash power. One stop separates each increment: 1/1, 1/2, 1/4, 1/8, etc. So when you increase your flash power, it puts out more light. Two things to consider when picking your flash power: Your batteries will be used up faster if you set your flash at a higher power AND it's one of the more difficult components to change on the fly.

Flash to Subject Distance
This is the most complex of the five variables. It involves the inverse square law and without getting into too much math, let me sum it up with this: The closer the flash is to the subject, the quicker the light falls off; the further the flash is from the subject, the more consistent the light is over a distance. If your eyes are glazed over at this point, just remember that all that translates into: Don't put your light stand real close to your subject (i.e. right next to the dance floor) or you will be changing your aperture constantly to get the correct exposure.

Just like it always does, ISO affects the overall sensitivity of your image to light. Changing your ISO will impact both the exposure of the ambient light and the flash exposure. When you use OCF, you are adding a significant amount of light into the equation so the nice thing is that you can use a lower ISO.

That's the brief overview of the variables that combine to determine exposure when using off-camera flash.

If you found this post helpful, and are interested in learning more, click here to opt-in for my free video series -- 6 Hacks to Eliminate Boring Low-Light Photos and Get You Creating Reception Images you LOVE! In it I share my best 6 tips for shooting with flash. If you are intimidated by flash and wanting to conquer it once and for all, this is a great place to start!
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