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Flash photography can be the most vexing skill to learn for many beginning -- and quite a few intermediate -- photographers. Available light is so much simpler because you can see it. You know exactly what your subject will look like, and can (in theory) take your time to compose, adjust, and prepare to get the shot you want.

There's no way to preview a flash picture. The light is only there for a tiny fraction of a second (1/20,000th, in some cases), so you don't see the problems until the photo is developed.

And those problems can be many, as anyone who's gotten frustrated by built-in, on-camera, or even off-camera flash can tell you: Washed out color. Flat features (especially with people). Red-eye. Dark shadows. A bright subject and a black background.

There is hope, however. Flash photography -- good flash photography -- is a step more complex than existing light, but it's not as daunting as you might have come to believe. There are more things to think about than with non-flash photography -- but then again, there are more things to think about when you use an SLR instead of a point-and-shoot. (If you don't know what an SLR is -- a single-lens reflex camera -- this article probably isn't for you.)

Entire books are devoted to flash photography. This is only one article. Therefore, it can't be all things to all flash users. It's worth reading if…

1. You own a fairly modern, non-point-and-shoot camera -- something built after the 1970s. It has to be one that allows you to adjust shutter speed, aperture, or (preferably) both. Control with point-and-shoot cameras is limited when it comes to flash, so most of this won't be applicable to those.

2. You know how to work your camera and your flash. You know how film speed, shutter speed, and aperture affect exposure, and you know how to attach your flash to the hot shoe and how to set it. You don't need to know all your flash's capabilities (if it's a fancy one); for our purposes, we'll stick to the fully automatic or TTL setting.

3. Your camera handles TTL (through the lens) flash. Since the 1970s, just about every decent SLR does. There are variations of TTL, such as Canon's A-TTL and E-TTL, but those are refinements we won't get into here. And you'll need to have a TTL flash unit designed -- or "dedicated" for your camera. If it's the same brand, chances are it is so dedicated. Third-party flashes, like those from Sunpak or Metz, need to be designed for your brand; you can buy versions of these flashes for Canon, Minolta, Nikon, Olympus, Pentax, and other brands.

- or -

3a. Your flash is automatic, with a built-in sensor. These work in a similar way to TTL flashes, but the sensor may not be as sophisticated as the ones built into the camera.

If this applies to you and you're looking to improve your flash photography, read on.

What Happens With Flash

To understand why flash pictures can be so troublesome, and what you can do about the problems you see, you first have to know what happens when you push that shutter release.

When you take a non-flash photo, here's what happens:

• You press the shutter release.
• Your camera measures the light in the scene, and determines the correct combination of aperture and shutter speed.
• The aperture opens a certain amount (say, f/8).
• The film is exposed for a certain amount of time (say, 1/250th of a second).

Those settings are determined by you (if you use your camera's M mode), or -- more likely, these days -- by your camera's metering system.

That metering system measures the light of the scene you're shooting, sometimes with incredible sophistication, dividing the scene into multiple zones and using complex algorithms that try to determine what the subject is, whether there's backlighting, and so forth.

The result, at least most of the time, is a photograph correctly exposed for both near and far subjects (e.g., your friend and the mountain behind him).

Flash photography is more complicated. In fact, you might says it's just about twice as complicated.

When take a flash picture, here's what happens:

• You press the shutter release.
• Your camera measures the light in the scene, and determines the correct combination of aperture and shutter speed. (That shutter speed is limited to the camera's flash-sync speed or slower -- usually 1/125 or 1/250.)
• The aperture opens a certain amount (say, f/8).
• The shutter opens.
• The flash fires.
• The flash metering system -- probably in the camera, but possibly on the flash itself for older models -- measures the light reflected from the subject, and turns off the flash when the correct amount of light has reached the camera. (This is usually somewhere between 1/500 and 1/25,000 of a second later.)
• The shutter closes a certain amount of time later (say, 1/250th of a second), based on that initial camera reading. (Exactly what light is measured and when depends on the camera, but this is essentially what happens, and is accurate enough for us.)

Yes, you read that right. In a tiny fraction of a second, your camera not only measures the entire scene you're photographing, but separately measures the light coming from the subject and shuts off the flash to expose it correctly.

And yes, you should be impressed. That's a mighty powerful (and fast) computer in your camera; it's measuring a light that appears for 1/10,000 of a second and cutting it off before it shines for too long, like 1/5,000 of a second. Wow.

Two, Two, Two Pictures in One

This bring up the most important thing to realize about flash photography: You are taking two separate pictures at the same time -- the subject and the background. Each is lit differently, each is exposed differently, and each is metered differently by different systems in your camera.

Once again: When you take a flash photo, you are taking two separate pictures at the same time.

If you understand this, you have just made a quantum leap towards better flash pictures.

Modern SLRs have incredibly sophisticated metering systems. In fact, they have two separate systems -- one that's controlling the flash, and one that's reading the rest of the scene.

The one controlling the flash is reading the light on the subject, because that's all the flash is illuminating. (Even big flash units have a maximum range of a few of dozen yards.) When the subject is lit properly, it cuts off the flash.

While the flash is lighting the subject or foreground, the rest of the scene is being lit by ambient light -- room lights, moonlight, city lights, or maybe no light at all. That part of the photo isn't affected much by the flash.

So let's say your camera has ISO100 film, and it's set at f/16 and 1/125 while you take a picture of your friend in a dimly lit room. The flash lights your friend just fine -- 1/125 of a second is plenty of time for the flash to go off. But the dimly lit room -- well, imagine if you didn't have a flash and used those settings. The room would come out underexposed.

So what's the result? A properly exposed friend (so to speak), and a dark, dark background.

Get it? You're taking two separate pictures: subject and background.

Let's try it again, this time with the camera set to let in more light -- say, f/4 and 1/30. Again, the camera's TTL system handles your friend just fine; it adjusts the flash as necessary. But this time, with a wider aperture and longer shutter speed, the background is a lot better exposed.

The idea is to have a properly exposed subject (thanks to the flash metering system) and a properly exposed background (thanks to the camera's 'regular' metering system).

Will that background be blurry? With a shutter speed of 1/30, probably (unless you're using a tripod). So you have to decide what's better -- a slightly blurry background you can see, or a picture of a friend against a dark nothingness.

How to Set Your Camera

If your camera is fully automatic and only fully automatic, these options won't apply to you, so skip to the next section.

Modern SLRs offer users a lot of options for taking a photo. Most have settings for fully-programmed mode (usually "P"), aperture-priority or -value mode (Nikon uses "A" while Canon uses "Av"), and shutter-priority or timer-value mode (Nikon: "S," Canon: "Tv"). Many also have a fully manual mode, as well as several preset modes such as "Portrait," "Close-up," "Landscape," etc.

A lot of people simply set the dial to fully automatic or "P" and let the camera do the work of setting the exposure. (If you're doing that, why did you bother getting a camera with all those features?) And when they take a flash picture, they often leave the camera on automatic as well. The end result: so-so flash photos.

Let's fix that.

To get better flash pictures, you need to start using your camera's capabilities. You need to turn the dial away from full-auto mode and take some control. Flash photos -- good flash photos -- require some extra care with your settings, but nothing that won't become second nature after a few rolls of film.

You should already know the three things that affect a photograph's exposure: film speed, shutter speed, and aperture. But those only apply to non-flash photos. For flash, there are two significant differences. First, you also have to worry about how far away your subject is, because a flash has a limited range. (Ever watch a night football or baseball game and see dozens of flashes going off in the crowd? Look carefully. Those people are wasting their film. They are way, way too far from the field for that flash to have any effect, so they're going to get dark -- probably black -- pictures. It's like trying to light the Grand Canyon with a candle.)

Second -- and here's the important thing about flash, for all those people worrying about shutter speed and aperture:

In flash photography, the shutter speed doesn't matter.

Got that? Your flash is way, way faster than your shutter speed -- it might be 1/5,000 of a second, 1/10,000, or even faster. Your camera's shutter speed probably maxes out at 1/4,000 of a second at best. It doesn't matter: Your flash is freezing your subject, even if your shutter speed is 1/8 and your subject is moving.

In flash photography, the shutter speed doesn't matter.

(Well, almost. Your shutter speed has to be at your flash sync speed or slower -- usually 1/250, 1/125, or 1/60 -- in order to make sure the entire frame of film is exposed to the flash's light. But the shutter speed has no bearing on the exposure of the subject when you're dealing with flash.)

That in mind, when you're taking a flash photo, you need to think a little differently about what settings -- P, Av (or A), Tv (or S), or M -- you use on your camera.

P Mode

If the background isn't important to you, you can put your camera on full automatic ("P" mode) and it'll handle exposing the subject correctly. But that won't help get rid of flat lighting, sharp shadows, and the other banes of flash photography. For better results, don't use it.

Tv or S Mode

"Time value" or "shutter priority" mode is not a good choice when you're using flash. First of all, remember what we said earlier: The shutter speed doesn't matter for the subject. So when you use Tv or S mode, you're only affecting the background exposure.

Unfortunately, that means the camera is setting the aperture automatically, and aperture does affect the flash picture -- both depth of field and the maximum distance your flash can cover. A smaller aperture means less light getting in, and thus a shorter range for your flash. If your subject is 10 feet away, it probably won't matter, but if you're shooting someone across the room, the camera may automatically set an aperture that's too small.

So, when you use Tv or S mode and thus ignore the aperture setting, you might end up with a poorly -- exposed subject.

Av or A Mode

A good choice for flash photos, aperture-value (or aperture-priority) mode lets the camera handle the shutter speed while you set the aperture. As with non-flash photos, setting the aperture changes the depth of field of the photo, so you can blur the background for portraits, for example.

With flash photography, the aperture setting is also important because smaller apertures reduce the effective distance of the flash. If you set the aperture to f/22, that tiny aperture is going to cut down how far your flash can reach. So while everything in sight might be in focus, nothing beyond a few yards will be lit.

Some flashes even have a table of film speeds and apertures on them to show you that if you use, for example, ISO400 film and set the aperture to f/16, the flash can only cover 28 feet.

There is, though, one potential disadvantage to using Av or A mode: Some cameras will ignore the presence of a flash at this setting, and automatically set a shutter speed to match the ambient light -- that is, a very slow shutter. Check to see what your camera does: Attach and turn on the flash, set the camera to A or Av, choose a small aperture like f/16, and see what shutter speed you get. (Some Canon cameras let you a shutter speed of 1/125 in Av mode if it detects a flash.) If the camera sets the shutter speed for something like 1/8 of a second or slower, Av or A mode might not be a good choice unless you're using a tripod or aren't worried about a blurred background.

Because of the potential for the camera to choose a long shutter speed in Av or A mode, often the best setting for flash photography is full -- manual.

M Mode

Using your camera's fully manual mode lets you decide how to handle the background, while letting the camera make sure the foreground is exposed correctly with the flash. In other words, it's not completely manual; you worry about the background and the subject is taken care of automatically.

What, you ask? Why did you spend all that money on a camera with the most sophisticated metering system ever devised if you're going to set it on -- gasp! -- manual? Because every brand and every camera handles 'automatic' modes (P, Av/A, or Tv/S) differently when it comes to flash. Some concentrate only on the subject. Some ignore the flash completely and expose only for ambient light. Some try to strike a balance. By using manual mode, you decide how you want the background to appear -- black, dark but visible, or correctly exposed.

So you have two choices: 1) read your camera manual and find out exactly how your camera handles its various automatic modes with flash, then decide if that's what you want it to do; or 2) set it to manual and adjust the camera to expose the background the way you want to.

If you vote for using manual mode (and that's probably the right choice), it means you need to know how to use your camera in manual mode. Even the most sophisticated SLRs have a display to tell you if your exposure is set correctly -- usually an LED that indicates over- and under-exposure, or maybe simply a + and - sign. Learn what it is and how to use it.

When you go to take your flash photo in M mode, look at what the camera is telling you about the exposure, and remember that it only applies to the background. The flash system will handle the subject. If you set the camera to expose properly (which will probably mean a slow shutter speed), the background will be properly lit. If that's what you want, you're set (although you might want a tripod or monopod to reduce blurring). If not, adjust the settings to your liking -- maybe making the background a stop or two darker, but still visible.

And keep in mind the aperture settings: Too small an aperture will mean a reduced flash range.

Whether you use manual mode or aperture-priority mode, after a few rolls (or maybe sooner) you'll get used to the settings. Yes, it sounds like there's a lot to keep track of, but it soon becomes second nature, and you'll find your flash photos that much better because of it.

Modifying Flash: Bounce, Diffused, Off-Camera, and Fill

Whether or not you take the time to understand how a flash works and why photos come out the way they do, there are some definite things you can do to get better flash photos. You can eliminate flat, washed-out faces, get rid of annoying background shadows, and generally end up with better shots. (Red-eye is a separate problem altogether -- see the sidebar.)

The reason most flash photos are, well, bad, is because they are lit with a bright light up close -- what photographers refer to as a small source. The flash tube is small compared to what you're photographing, e.g., a person, and that leads to distinct shadows and harsh lighting.

The sun is also a small source, not because it's physically small, but because it appears small thanks to its distance. But when it's cloudy, the sun becomes a large source because the entire sky is a light, not just that one bright yellow spot. In cloudy weather, shadows become less distinct, lighting is more subtle, and photos come out better (lighting-wise, if not mood-wise).

There are two basic ways to get better photos from your flash. One is to turn the small source that is your flash into a larger source by either diffusing it or bouncing it. The other is to move the flash off camera -- to one side or above -- to avoid that in-the-headlights, flat-lighting look.

Bounce Flash. Many modern flashes have the ability to bounce -- that is, the flash head can pivot left and right and/or up and down so the flash points somewhere other than straight ahead ("direct flash"). The idea is that rather than shine the light directly at your subject, you shine it on a nearby wall or ceiling which then reflects light onto your subject. This bounced light is a much larger source (a ceiling being somewhat larger than a flash head), and the result is a more even, less harsh light.

With modern TTL flashes, getting correct exposure with bounced light isn't a problem. The camera does what it did with direct flash: measures the light and shuts the flash when it has flashed enough. It does the same thing with bounced light, so, as long as your camera supports TTL, you don't have to worry about metering.

But there are some disadvantages to bouncing a flash from a ceiling or wall. First, there might not be a convenient one -- imagine standing in the middle of a store with its high ceiling and distant walls.

Second, if you bounce a flash, the distance the light has to cover increases -- possibly by a lot. Your friend may be five feet in front of you, but if you bounce the light off a ceiling that's five feet above your head, the light has to travel at least 10 feet to get to your friend. Remember that flashes have a limited firing range, and flash light falls off quickly the farther away you get from your subject. A bounced flash is a weaker flash.

Third, you need to aim the flash carefully. When you use direct flash -- pointing at your subject -- you don't have to aim; the flash is pointed in the same direction as the lens. But when you bounce, you need to do a bit of geometry to make sure that you don't bounce the flash from a wall to a spot 20 feet behind your subject.

Finally, if you aren't bouncing a flash off a white or near -- white wall or ceiling, the light will take on the color of that wall or ceiling. You might end up with a friend who's green, red, or who-knows-what.

Diffused Flash. Another way to turn your small flash head into a larger source is to use a diffuser -- something that spreads the light out a bit as it leaves the flash. A simple, if ugly, diffuser would be one of those translucent plastic gallon milk jugs. Cut a hole in one (a clean, dry one!) that's the size of your flash head, and stick the flash head into it. Now when it flashes, the entire milk carton will light up. And because a gallon milk carton is larger than the bare flash, the light is diffused a bit and shadows are less harsh.

A nicer way to achieve the same effect is to buy a flash-head diffuser. Companies such as Lumiquest (www.lumiquest.com) make a variety of what are sometimes called "mini-softboxes" that fit over flash heads, often using Velcro to keep them in place. They look nicer than a milk carton, and they can fold (or sometimes deflate!) to fit into a camera bag.

There are also small umbrellas that fit onto camera flashes. You've seen large versions in photo studios -- they look like rain umbrellas, but with a white or silver lining. You bounce the light off the inside of it, and that white or silver lining turns your tiny flash head into a three-foot diameter light. (Studio lights obviously use large umbrellas, but the ones that can be mounted on a small flash are somewhat smaller.)

As with bounce flash, there are some downsides to diffusing your flash. First, you lose a significant amount of output. Maybe not enough to make a difference with a subject a few yards away, but enough to limit the range of the flash when you're trying to take a picture of something across a large room.

Second, a diffuser certainly increases the size of the light source, but not that much. It's still a small source of light, and you'll still have fairly well-defined shadows. But it will be a lot better than a flash without one.

Off-camera Flash. One of the best reasons to use your flash off-camera is the rig you use. What I mean is, it looks very cool to non-photographers. Flashes mounted on cameras are a dime a dozen, but when that flash is on a metal bracket above or to the side, people will feel compelled to say, "Fancy setup!" with some degree of awe.

Setting up off-camera flash is simple, although it requires a bit more hardware than simply attaching a diffuser.

The hot shoe on your camera -- the connection where you fit your flash -- has several electrical contacts on it that let the flash and camera communicate. You want to preserve those connections when you move the camera away, so you need an off-camera cord made for your model camera. (If you own a Canon camera, get a Canon cord. Ditto for Nikon, Minolta, or whatever. You want to make sure the cord maintains all the connections between camera and flash.)

These cost anywhere from $20 to $60, and consist of three things: a connection that fits on your camera, a (usually) coiled cord a few feet long, and a connection for your flash to fit into. Now, instead of being attached to your camera, the flash is on a cord; you can lift it up, move it to the side, or whatever.

Of course, you might be able to operate your camera with one hand while holding the flash with the other, but that gets awkward quickly. To the rescue are off-camera brackets made by companies like Stroboframe. These metal doohickies attach to your camera, usually via the tripod hole, and have a place to attach your flash so it ends up above or to the side, connected by your off-camera cord. Basically, it's a third hand that holds and directs the flash.

By mounting your flash off the camera, you can avoid that flat, washed-out look common to a lot of flash photos. Portraits lit from the side are much nicer than those lit straight on, and even moving the flash a little bit can eliminate red-eye. Lighting someone from above -- even if the flash is only a foot or so higher -- can make a dramatic difference in the quality of the light.

Disadvantages to off-camera flash? The expense, for one. The off-camera cords aren't cheap. And although you can easily build your own flash bracket with aluminum strips from Home Depot (get 1" x 1/8"), it's much less of a headache to buy one. Stroboframe and other professional brands are more expensive, but there are plenty of no-name brackets that are cheap enough to play around with.

An off-camera setup is also a bit unwieldy. That bracket can extend a foot or more above the camera, which means there's no chance of being unobtrusive. That's the down side to people saying, "Fancy setup!" You can't just blend in a crowd. (There's an upside. You look like a professional photographer, so you might be able to get into press-only areas. But don't bet on it.)

Fill Flash. When you think of using flash, you usually think of dark rooms or night scenes. But there are some good times to use flash even in bright light. By using a flash even when there's plenty of illumination, you can fill in dark areas of your subject -- that's why it's called fill flash.

The most obvious use is if you're taking a photo of someone who's back is to the sun. That puts her face in shadow. Using the flash will fill in that darkness, and today's cameras are smart enough to realize there's plenty of light -- they'll reduce the flash's output to fill in the shadows without washing out the subject's features.

Even good point-and-shoot cameras can do this: Simply change the flash setting from 'auto' to 'always on' and take your daylight photo. The flash will go off and fill in those shadows. The results might not be as good as with a full-featured SLR, but they'll probably be better than using no flash.

Flash photography is not as simple as existing-light photography (not that that's simple!), but it doesn't have to be something to avoid. It takes practice. It takes some extra thought. It might take an investment in a little extra hardware, like a diffuser or off-camera setup. But the end results are worth it: Great pictures indoors as well as out, without buying 1600-speed film, and the admiration of your friends and family next time they flip through your photo album.

If you've been avoiding using your flash, stop. Dust it off, recharge the batteries, and take the time to learn how to use it right.

Red-Eye

Ah, red-eye. The single most common problem with flash photos. Unless you're taking pictures of demons walking the earth, the most annoying thing to see are your friends and relatives with glowing red eyes.

Red-eye occurs because, in the dark, people's (and animals') pupils dilate -- they expand to let in more light. Your flash goes off and is reflected through that large pupil onto the retina. The retina has lots of blood vessels -- red ones, as you might imagine. Thus, red-eye is simply a photo of someone's retinas.

There are two ways to prevent red-eye. One is to move the flash so it doesn't shine directly into your subjects' eyes, and thus doesn't bounce off their retinas. off-camera flash will do that, as will bouncing it off a ceiling or wall.

The other option is to trick their pupils into contracting. That's what 'red-eye reduction mode' on cameras does -- it fires a "pre-flash" that causes the pupils to contract, then takes the photo before those pupils can dilate again.

Guide Numbers

All flashes are not created equal. Besides things like the ability to swivel and pivot, and the ability to adjust things like output level, every flash has a guide number. Essentially, it's a measurement of how powerful it is -- how much light it puts out.

Of course, it's not quite that simple. A flash's guide number is dependent on the film speed and is either based on English or Metric measurements. That means a number isn't just a number: It's a number based on such-and-such a film and measured in either feet or meters.

Luckily, most guide numbers are expressed based on ISO100 film. But sometimes it will be based in meters, sometimes in feet. So make sure to compare apples to apples -- make sure that both Flash A and Flash B have their guide numbers expressed in either 'ISO100 in feet' or 'ISO100 in meters' (e.g., "a maximum guide number of 223 -- ISO 100 in ft)" or "guide number 54 for ISO 100 in metres").

Guide numbers also need to take into account the focal length of your lens. Usually, the guide number is assuming a 50mm lens, but you might also see "Guide number 198 for ISO 100 in feet at 105 mm focal length." So not only do you need to compare apples to apples, you need to compare Granny Smith apples to Granny Smith apples.

All that said, a flash's guide number is the f/stop required for correct exposure at a certain distance with a certain film speed. A high guide number (a more powerful flash) can use a larger f/stop (a smaller aperture) at a given distance.

You can use a guide number in one or two ways. If you're interested, you can use it to calculate the f/stop you need to get correct exposure with your flash at a given distance and with a given film. More likely, though, you'll use it simply to compare one flash to another.

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