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Shedding Light on Flash – Part 1

The little, bright light tube that comes with a camera since the advent of automatic exposure has been one of the greatest mysteries for camera owners. Most know (or think they know) that the little flash unit is provided to provide light when the sun goes down.

While it used to be that simple during the days when intelligent metering was absent, today’s camera and flash allow users to have much more control on how the flash works with the camera as an individual unit. You’ll be surprised on how simple the concept really is, and I hope I can demystify the simple flash and improve your day-to-day photography.

Note that I won’t be covering the topic in detail as mastering flash photography is an art by itself.

There are so many things you can do with a flash unit that you’re limited only by your creativity. In addition, we’re not covering issues like flash settings if you’re using a manual flash unit or choose to control the flash without automated metering (i.e. ETTL, PTTL, etc.) I’ll provide you with a simple primer that will shed light (pardon the pun) on the whole subject matter, especially if you’re a beginner.

You only have to remember three things as soon as your flash is turned on (either when you pop-up your on-cam flash or attach your hot shoe flash).


What you need to do before we start: 1) Set your camera to Manual mode. 2) Set your flash to Auto ETTL mode (for external flash units) and make sure the flash exposure compensation is set to “off” or “0”, if you don’t have an idea what I’m referring to, read the user’s manual. I’ll show you a set of photos and they’ll be very self-explanatory.

Note: All images in this article used a built-in flash, not external flash. You’ll benefit more with an external flash unit, read more about why a flash is useful in my “Get a Flash First to Improve Your Photos” article.

SUBJECT – The Horse

Background/Ambient – The wall and the shadow behind the SUBJECT. The fluorescent light flickers a little, so pardon the light shift on some of the photos.

1/60sec @ f/4 ISO400 Auto WB

1/60sec @ f/4 ISO400 Auto WB

Photo 1: “Standard” Full Auto Shot

This photo was taken in Full Auto mode. On my Canon, that’s the green square on the mode dial. It should be the same for virtually all modern cameras. The setting chosen by the camera was 1/60 @ F4. Usually when automated settings are used, the camera synchs the shutter at 1/60sec (point and shoot or DSLR, doesn’t matter, they all prefer 1/60sec for some reason). The result is a harshly lit subject with SHARP defined shadows and dark background. Most of the shots taken with full auto flash look like this, an overlit subject with a really dark background. Try it with your cam before we proceed. Remember to compare the horse’s exposure, the wall’s exposure, and the SHADOW it creates.

In the next set of photos we alter the CAMERA EXPOSURE settings only. The flash exposure compensation stays at “0”.

Photo 2: Wall metered to +1/2 (exposure indicator is leaning towards the + side), flash setting untouched.

1/50 sec @ f/4 ISO400 Auto WB, Flash Compensation = 0

1/50 sec @ f/4 ISO400 Auto WB, Flash Compensation = 0

So what’s the difference? First, the horse is exposed by the flash almost the same manner as the “Auto” shot, but since we slowed down the exposure compared to the Auto shot, we let in more AMBIENT (background) light, hence the wall is now more WHITE rather than GREY.

The horse is a little brighter overall as more scattered light from the flash is scattered around the horse. What you have to compare in all these shots in this set is the SHADOW behind the horse. This is a pretty balanced shot with the ambient registering correctly while the horse is exposed well. You can reduce the harsh shadows with some diffusing (softening of the light) or adding a reflector, but let’s skip that for now.

Photo 3:  Wall metered to +1, flash setting unchanged.


1/25 sec @ f/4 ISO400 Auto WB, Flash Compensation = 0

This is almost like the previous photo, but I slowed down the shutter speed even more (1 stop) at 1/25sec, the aperture, ISO, and flash compensation is unchanged. What do you see? The horse is exposed almost exactly the same as the Photo #2, but the background is even brighter now due to the slower shutter speed.

In addition, look at the shadows, since more light is captured from the wall, the shadow is a less harsh than the first two photographs! Again, look at the horse’s ribbon, they’re almost identical, the wall wasn’t, therefore the shadow wasn’t as well.

Photo #3 – Wall metered at +2, no flash adjustments made


1/10 sec @ f/4 ISO400 Auto WB, Flash Compensation = 0

Just like the previous photo, only more exposure on the wall. Again, the horse is lit the same way but the background is a lot brighter. Note the lighter shadow again.

Photo #4 – Wall metered at +3, no flash adjustments made

Taking it one step further, I exposed the background at 1/5 sec and look at what happened to the background and shadow, while the horse looks the same as the previous images.

1/5 sec @ f/4 ISO 400

1/5 sec @ f/4 ISO 400 Auto WB, Flash Compensation = 0

Now you know that changing the camera’s exposure (shutter/aperture/ISO) changes how the BACKGROUND is exposed and doesn’t affect the SUBJECT significantly.

The following set of photos are manipulated by the FLASH’S EXPOSURE only. This is done by changing the FLASH EXPOSURE COMPENSATION setting in your camera or flash unit. We’ll start off with Photo #4 as reference as I like how the horse and background exposures are balanced.

This is our “zero flash compensation” image.


1/10 sec @ f/4 ISO400 Auto WB, Flash Compensation = 0

Photo # 5: Camera setting: 1/10sec @ f/4 ISO400, Flash compensation set at -2.

1/10sec @ f/4 ISO400 Auto WB - Flash Compensation -2EV

1/10sec @ f/4 ISO400 Auto WB - Flash Compensation -2

The background looks a little dark here because the overhead fluorescent light flickered, the background should be the same as the reference image, apologies for that. Anyway, what you need to take note here is the horse.

Notice how dark it is now because of our flash setting.

Photo #6 – Same background exposure of 1/10 @ f4 – ISO 400, but flash compensation set at +2

1/10sec @ f/4 ISO400 Auto WB - Flash Compensation +2

1/10sec @ f/4 ISO400 Auto WB - Flash Compensation +2

Observe that when you alter the flash’s power in a small room, the effect on the background and ambient is more pronouced than a large room or outdoors. There’s not a whole lot the photographer can do to prevent the flash’s output from spilling over the side and front of the subject in this case, hence the overexposure of the whole scene.

Notice how much the horse is lit now, but the SHADOW QUALITY is identical to the rest of the photos because the ambient at the back is the same. Go try it out. Now here are some real-world applications, all the photos below only utilized the pop-up, built-in flash of my DSLR. If you have a more powerful and flexible external flash gun, the effect and possibilities are even greater. The exposures are not adjusted in any way.

Subject – Sky and Exercise Stand

Here’s a late afternoon scene with lovely cloud formation after a heavy downpour.

Photo #7 – Metered for the clouds only.

1/200 @ f/16 ISO 100 - FLASH OFF.

1/200 @ f/4 ISO 100 - FLASH OFF.

I set my shutter to 1/200 as this is my camera’s fastest x-sync speed (fastest shutter speed where a flash can be used) then I adjusted my aperture until I get the sky details I wanted. In this case, f/16. Note that I have no details at all on the foreground subject’s surface, the result was a silhouette.

Photo #8 -Metered the foreground only.

1/100 sec @ f/4 ISO 100, No flash

1/100 sec @ f/4 ISO 100, No flash

Again, I adjusted the shutter to 1/100 but opened up my aperture to f/4 so that the foreground can be exposed. Note that the sky has lost all its details from overexposure. So this is the extreme opposite of Photo #7. Let’s see if we can have some sort of middle ground between the two exposures.

Photo #9: Compromise between the two exposures and added flash.

1/125 sec @ f/22 ISO 400 with +2 Flash Compensation

1/125 sec @ f/22 ISO 400 with +2 Flash Compensation

Isn’t this better if you want to capture both the clouds and the foreground?

So what happened here?

First, I bumped the ISO up to 400, I did so to allow the camera to capture more light without resorting to long exposures. Second, I decreased the shutter speed from Photo #7 to allow more light in, this resulted to some lost details in the sky, but it’s not washed out. I’m OK with that. The flash was then popped-up and I added +2 flash exposure compensation (FEC) as the pop-up flash is too small to reach my FOREGROUND subject if unadjusted. So there you have it, the shutter/aperture/ISO is for the cloud and background exposure, while the flash lifted the dark foreground shadows. Want another practical example? Here’s another one.

Subject – Sky and Court

Photo #10: Metered the Sky

1/320sec @ f/22 ISO 400 NO FLASH

1/320sec @ f/22 ISO 400 NO FLASH

Like Photo #7, I exposed for cloud details but my basketball court is now too underexposed. It’s not a silhouette as the board is translucent, but you don’t see any details on the ring and net’s surface.

Photo #11 – Metered for the basketball court.

1/320sec @ f/8 ISO 400 NO FLASH

1/320sec @ f/8 ISO 400 NO FLASH

Now I metered for the basketball court. We see all the nice details of the foreground subject (board, ring, net, and post) but lost the sky completely. I merely adjusted the aperture in this case. Let’s find a compromise again using our little pop-up flash!

Photo #12: Meter + Flash

1/200 @ f/16 ISO 400 FEC +2

1/200 @ f/16 ISO 400 FEC +2

Again, I have to determine how much sky am I willing to lose or dark of a foreground is acceptable, so I chose a slower shutter speed of 1/200 sec (my cam’s max sync speed again), aperture is set half-way between the two previous exposures at f/16, then popped the flash and used +2 FEC again as the distance is rather far for my built-in flash to reach. I think this is a decent compromise.

If you can edit this further with your favorite post-processing software, you can brighten up the foreground further and lift some of the trees shadows up even more, but without post-processing, this is a decent compromise from the previous 2 exposures.

Try it out yourself!

Here are some real-life photos that you might encounter. Same principle and equipment were used.

The sun is off the the side and behind the subject, if I only metered on my son’s face, the background will be totally washed out and the trees will not render as dark green. I exposed for the trees and popped my built-in flash at -1FEC to lift the shadows from my subject’s face. Note the bright white spot in his eyes, that’s the flash itself.

This shot was taken at high noon, I exposed for the beautiful clouds above the boat man and then lifted the shadow of the man with my pop-up flash. Again, if I used a reflector or a larger flash gun, the result will be more dramatic, but a pop-up flash was the most convenient at that time.

Same thing, expose for the sky, the lifted the foreground subject with flash.

As you can see, your flash is most useful as a supplementary light during daytime and it’s not just for dark party shots.

Like a good TV ad… BUT WAIT! THERE’S MORE!

Read Part II of Shedding Light on Flash where we’ll talk about using your flash indoors without the headlight-on-deer look and harsh hotspots – even with a standard pop-up flash or pocket camera!

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