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This article is part of the ‘Portrait Lighting For Beginners’ series. This series is meant to help you go from a beginning photographer to making beautiful portraits.

In order to take high quality images with flash in the studio, you’ve got to learn to go manual, both on the camera and on the flashes. But this can be a little daunting for a new photographer, and one of the reasons for this is that the normal rules you learned about exposure are a little different with flash. You start taking pictures, start trying to adjust the exposure, but the effect isn’t what you expected. This is an area that I feel isn’t explained much in books or on the web. Photographers are left to figure out the why on their own. Well not if you’re a Sublime Light reader.

The Rule of Thumb
When using flash, to change the exposure you adjust aperture. Adjusting shutter speed will change ambient light exposure.

Changing Shutter Speed
Your camera’s max flash sync speed is probably somewhere around 1/250th of a second (check your manual for yours). This means that to sync up with the flash correctly, you can’t go any faster. Now compare that with the duration of a flash burst, which depending on the power you’ve chosen, could be somewhere in the 1/4000th of a second range.

So just stop and think about this for a second. Unlike ambient light that builds up on the sensor the whole time the shutter is open, flash light is constant no matter what the shutter speed. The only way to grab less light out of that flash burst would be to choose a speed faster than the burst. But you’re constrained by the max sync speed. So you could change the shutter speed all day, speeding it up, but you’ll always grab the same amount of light from that flash.

The bottom line is that the shutter speed will have no affect on the exposure of the area of your image that’s lit by the flash. Consider the image below. The flash power wasn’t changed, and the aperture was kept constant. I only changed the shutter speed. As you can see, the images all have the same exposure. Had I gone slow enough, I would start to pick up ambient light from the room.

All three shot at f8

In future articles we’re going to talk about outdoor portraits and how to balance your flash lighting with the ambient light. That’s where the shutter speed comes in.

Changing Aperture
Just as a refresher, when you change the aperture, you’re changing the size of the hole in the lens that allows light through. A lower aperture number means the hole is bigger, letting more light in.

So now that we know you can change the shutter speed all day long with no effect, the only other setting to play with is the aperture. If you want to change the exposure of a flash lit photo, simply adjust the aperture setting. A lower number makes your image brighter and a higher number makes your image darker. Take a look at this next series of images, all shot at the same shutter speed, but the aperture was changed.

All three shot at 1/250

Simple huh? Just remember that when you change aperture, you’re also changing the depth of field. So if your intention was to get a shot with someone’s face in focus and their body further away out of focus, changing the aperture to a higher number will bring their body more into focus. In this case, you’re better off adjusting your ISO setting, adjusting your flash power, or moving your flash further away.

Do You Need A Light Meter?
Some photographers will tell you to get a light meter. But do you really need one? After all, they’re expensive, they’re one more thing to carry, and in my opinion, they slow you down. I’m not worried about getting my exposure perfect to within 1/10th of a stop. I want to produce a good image and that’s it. So I don’t even own one.

After you’ve set up your lights and exposure a few times, you start to get a feel for how to set everything. If you take a mental note of the setup, then the next time you’ll have a good starting point. Then you don’t need a meter to tell you what to set your camera to.

For the images above, I picked the settings that seemed right to me and took a picture. The exposure was correct on the first frame. And now that you know the rule, you know that you can fix the exposure in seconds because you know how. So even if you’re off by a couple of stops, five seconds of time will get you the right exposure.

Your Turn
The best way to get this stuff burned in your brain is to do it. So get out the flash and camera, steal some of your kids’ toys, and take some pictures. Take mental notes of the settings, and you’ll be all set for next time.

Then, post your results to the Sublime Light photo pool. Seriously, join in the fun. We’re getting together a great group of people and some really fantastic photos are showing up in the pool.

And if you have questions, put your question in the Sublime Light forum.