Flash photography

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Camera flash

 

Flash is a powerful tool in imaging.  Flash allows you to bring more light to a subject and to freeze action that is too fast for even the camera's shutter.  Whether built in to the camera, attached to the hot shoe, or connected by wires or a wireless link, mastering flash will help make you a better photographer.

 

 

A flash unit consists of a small xenon filled tube and the electronics to supply the tube with a brief jolt of high-voltage electricity. Flash units are configured in a number of different ways:

Whatever the type of flash you get, one thing to keep in mind is the Guide Number This is a number, usually expressed in feet at a given ISO, which indicates the relative power of the flash.  A higher number means a more powerful flash.  For instance, two flash units may have guide numbers of 50 and 100 with ISO 200 film.  This would mean that the former is powerful enough (with a normal lens) to illuminate a target 50 feet away.  The second unit is more powerful, since it would reach 100 feet.

Most flashes are designed to work at shutter speeds from 1/60 to 1/125 of a second, this is called the sync speed.  Newer cameras have a wider range.  On the other hand, the shutter speed is somewhat irrelevant in situations where the flash will be the main light.  Under these conditions, the brief (thousandths of a second) flash burst will freeze motion

in a camera, flash synchronization, also known as flash sync or flash synch, is required for the firing of a photographic flash to coincide with the shutter admitting light to the photographic film.In mechanical cameras, the synchronization mechanism usually consists of an electrical contact within theshuttermechanism. In electronic digital cameras, the mechanism is usually a programmable electronic timing circuit, which may take input from a mechanical shutter contact in some cameras. The electrical connection will be either by means of a cable with a standardised coaxial PC (for Prontor/Compur) 3 mm connector, or via contacts in an accessory mount hot shoe bracket.

Other factors affect the useful range at which a flash will work.  A wide-angle lens requires more light than a normal lens, for instance, because at a given range a larger area must be lit.  Some cameras and flash communicate with each other; the hot-shoe flash shown above can find out from the camera what lens is mounted and then zoom the flash head (automatically, via a motor) to provide the right angle of flash to complement the lens.  Multipliers, extension tubes and other accessories may also affect flash exposure.

Flash used to be a tricky business, but electronics has changed all that.  Newer cameras either read the flash exposure by measuring the light as it is reflected off the film itself during exposure, or they fire a pre-flash and use special metering cells to determine the proper flash exposure.  In the former case, the camera simply shuts off the flash when the right amount of light has reached the film.  In the latter, the camera simply fires the flash for the correct amount of time.  Most cameras can easily do "fill-flash" as well. In fill flash, the camera makes an exposure using the natural light that is very close to correct, and fires the flash for a very brief time.  This brief burst of flash "fills" in the shadows and brightens colors.  Because the exposure was largely made using ambient light, however, objects in the background appear normal, not black as can happen when flash is used as the main light.

1. Use extension cords or wireless remote units to get the flash away from the camera.2. If the flash is too harsh (particularly with close subjects), use a softbox or place a tissue over the flash head.3. Many flash units have a bounce capability, which allows you to swivel the flash head and bounce the light off a ceiling or wall. This results in a softer, more natural light.4. Beware of shadows cast by objects caught in the flash light.

If you are using flash in any of the modes mentioned above, remember that large objects or objects close to the flash will reflect a lot of light back at the flash.  If they are large in the field of view, they can adversely affect the exposure, if they are small they will likely be over or underexposed themselves.  For instance, a blade of grass in the foreground of a macro shot may become completely white in the image, or the camera may use so much flash trying to turn a black dog into a gray one that the rest of the picture is overexposed.

5. Fresher batteries will allow the flash to recycle faster. Also, the flash will recycle faster when the subject is light colored and close. Dark, distant objects will use up all the flash's power and cause a longer recycling time. Pressing the shutter before the flash has recycled may result in a blurred or dark shot6. Many flash units have a test button and a flash confirmation light. Firing the test button will produce a flash; if there is enough light the confirmation light (usually green) will come on. This lets you know if you have enough light before you waste film.7. On overcast or rainy days, fill-flash can bring out colors.8. Some flash units have a slave feature. This means that they will fire when they detect a flash from another unit. This is handy in two cases:9. A Flash Extender can allow you to use a flash with a telephoto lens at greater distances than the flash would normally reach. Flash extenders focus the flash light.

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Flash

Your camera is equipped with a built-in flash that offers a red-eye reduction feature. The flash has an effective range of approximately 1.6 to 9.8 ft. (0.68 to 3 m). There are four Flash settings:

 Auto—The flash fires automatically when you press the SHUTTER button and the camera determines that there is not enough light.

Red-eye— If the camera determines that there is not enough light, the flash fires once when you press the SHUTTER button to reduce the chance of red-eye and then flashes a second time, 600 milliseconds later, when the picture is taken.

 Fill—The flash fires every time you press the SHUTTER button. Use this setting when the lighting is poor or when your subject is lit from behind.

 Off—The flash is turned off and will not fire. If you turn the flash off, the next time you turn the camera on, the camera defaults to the Auto flash setting.

 flash (photography)

In photography, a flash is a device that produces an instantaneous flash of artifical light (typically around 1/3000 of a second) at a color tempereatur of about 5500K to help illuminate a scene. While flashes can be used for a variety of reasons (e.g. capturing quickly moving objects, creating a different temperature light than the ambient light) they are mostly used to illuminate scenes that do not have enough available light to adequately expose the photograph The term flash can either refer to the flash of light itself, or as a colloquialism for the electronic flash unit which discharges the flash of light. The vast majority of flash units today are electronic, having evolved from single-use flash-bulbs and flammable powders.

In lower-end consumer photography, flash units are commonly built directly into the camera, while higher-end cameras allow separate flash units to be mounted via a standardized accessory mount bracket. In professional studio photography, flashes often take the form of large, standalone units, or studio strobes, that are powered by special battery packs and synchronized with the camera from either aflash

Balanced fill-in flash is a wonderful technique that can either add life to otherwise ordinary pictures, or in some cases, rescue images that previously might have not been useable.  And what’s really nice is that fill-in flash can be done with fully automatic exposure control – no special manual settings are needed, unless you want to put your own personal touch on your pictures.  You can even do fill-in flash using the built-in flash unit on cameras .

What exactly is balanced fill-in flash?

 

By definition, a fill-flash picture is one in which the ambient light in the background – sunlight outdoors, room lighting in an indoor shot, and so on – is properly exposed and therefore normally visible in the picture.  But along with this, flash has been used, and subjects in the foreground of the picture are illuminated by this extra burst of flash.  With a properly exposed background, and also a flash-illuminated subject that’s got proper flash exposure, the two light sources (flash and ambient light in the scene) are balanced, and neither will appear overly dark or light.  This usually gives us a very natural-looking picture.  It can also brighten otherwise subdued faces, lighten shadows from harsh sunlight, or sometimes just add a little sparkle in a subject’s eyes.

First off, there’s no special trick to taking balanced-fill flash pictures outdoors in daylight, even in bright sunlight.  With the camera in any automatic exposure mode such as Program (P), Tv, or Av, just pop-up the built-in flash by pressing the flash-on button, or alternatively mount and turn on an EX series Canon Speedlite flash unit.  The camera “knows” the flash has been activated, and all you need to do is focus and shoot the picture.  In the Tv and Av modes, if you’ve set a shutter speed (in Tv) or aperture (in Av) that simply won’t enable a proper exposure of the daylight in the scene, the opposite value blinks on and off in your viewfinder;  just switch to a different shutter speed or aperture, until the display stops blinking on and off.  You’re ready to take the picture.

There’s no need to take the flash out of its automatic “E-TTL” setting (unless for some reason you want to use manual flash with an accessory EOS speedlite).  The beauty of fill-in flash with a modern SLR is that the camera adjusts background exposure and flash exposure automatically, with little input required from the user.

To preserve a natural look in fill-flash pictures, the camera deliberately tends to reduce the intensity of your flash output when it detects that you’ve properly exposed the ambient light in your background.  The intent is to give you fill-flash pictures with foreground subjects that don’t appear to obviously have been blasted with frontal flash.  (This occurs automatically, with no input required from the photographer.)  This way, shadows are gently filled-in, without looking like your subject was lit-up by a searchlight. 

When you have a subject that is primarily lit by sunlight, and you’re just trying to lighten a few shadows on his or her face, this automatic flash reduction tendency works very well.  But sometimes, you may be asking the flash to do more than just fill-in a few shadows.  If your subject is heavily back-lit, and entirely in shadow, you may want the flash to become the primary source of light.  An example might be a shot of a person against the setting sun.  With no flash, you’d likely get a silhouette.  But if you simply turn on your flash and take a picture at normal settings, you might end up with an effect that still looks like a silhouette.  The flash may not have lit your subject up much at all.  What when wrong?

 

Types of flashes

Flash bulbs

The earliest flashes consisted of a quantity of mangnesium flash powder that was ignited by hand. Later, magnesium filaments were contained in flash bulbs, and electrically ignited by a contact in the camera shutter; such a bulb could only be used once, and was too hot to handle immediately after use, but the confinement of what would otherwise have amounted to a small explosion was an important advance. A later innovation was coating flashbulbs with a plastic coating to improve spectral quality as well as providing protection from the rare occasion when a flashbulb would crack during a flash.

Flashbulbs took longer to achieve full brightness and burned for a longer duration than electronic flashes, and slower shutter speeds (typically from 1/10 to 1/50 of a second) were used on cameras to ensure proper synchronization. One of the most widely used flash bulbs up through the 1960s was the number 25. This is the large (approximately 1 inch (25mm) in diameter) flash bulb often shown used by newspapermen in period movies, usually attached to a press camera or a twin lens reflex camera

 

Flash accessries

Fill-in flash pictures in daylight:
Using Flash Exposure Compensation
in fill-flash pictures:


The amount of flash illumination in a fill-in flash

 picture is a starting point.  And while it often

works beautifully, in instances like the sunset

shot, all the bright sunlight in the scene can fool

 the camera into thinking that not much flash is

needed.  But as we said, in a totally back-lit

scene, you’re basically asking the flash to be

the main source of light hitting your subject. 

 How to get more flash on the scene?  Easy. 

 Use your camera’s Flash Exposure

 

Limits with fill-in flash in daylight:

Changing the brightness of
the background:
Balanced-fill flash can also easily be done when you’re indoors, or outdoors at night.  In a typical flash snapshot in these conditions, we’re used to seeing a brightly-lit subject, with a black or nearly-black background.  This happens because the ambient light in the room or in the scene was underexposed, but the flash illumination on the subject was correct.  To get a more natural-looking, balanced-fill result in these scenes, we need to extend the exposure so that more ambient light is recorded in the scene.

Any time you’re working at slow shutter speeds to blend-in natural light in a flash picture, remember to be careful to hold the camera very steadily, and be sure your subjects are stationary as well.  Any movement will usually result in blurs or ghost images.  In other words, if you’re looking for sharp action pictures with flash at a high school basketball game, it’s not the time to use the balanced-fill technique.

Again, the camera will usually tend to reduce the flash output when you properly expose your backgrounds, so that the flash isn’t obvious in the lighting of the final picture.  Often, this gives a very natural looking result.  But if you want more or less flash output, you can easily achieve this with your Flash Exposure Compensation.  And you can also subdue the ambient light in your background by darkening it with standard Exposure Compensation, or alternatively brighten it by adjusting Exposure Compensation in the “plus” direction.  Once again, this is entirely separate from adjusting flash power up or down with the Flash Exposure Compensation.  Experimenting with the two will give you a tremendous amount of control over the final look of your fill-in flash pictures.

Another common flashbulb-based device was the Flipflash which included ten or so bulbs in a single unit. The name derived from the fact that once half the flashes had been used up, the unit had to be flipped and re-inserted to use the remainder.

 

Modern flash technology

today's flash units are often electronic xenon flash lamps. An electronic flash contains a tube filled with xenon gas, where electricity of high voltage is discharged to generate an electrical arc that emits a short flash of light. (A typical duration of the light impulse is 1/1000 second.) As of 2003 the majority of cameras targeted for consumer use have an electronic flash unit built in.

Another type of flash unit are microflashes, which are special, high-voltage flash units designed to discharge a flash of light with an exceptionally quick, sub-microsecond duration. These are commonly used by scientists or engineers for examining extremely fast moving objects or reactions, famous for producing images of bullets tearing through objects like lightbulbs or balloons (see Harold Eugene Edgerton).

Studio flashes usually contain a modeling light, which is an incandescent light bulb placed close to the flash tube. The continuous illumination of a modeling light helps in visualizing the effect of the flash.

Technique

A flash is commonly used indoors as the main light source, because there is not enough other light for a desired shutter speed. A fill flash is a low powered flash mixed with ambient light, and is often used to illuminate shadows on the side of a subject facing the camera. Another technique, bouncing a flash, involves pointing a flash upwards off of a surface, often a white celling, where it is reflected back onto the subject. Bouncing creates a more natural light effect and lessens shadows and glare but requires more flash power than a direct flash.

Part of the bounced light can be also aimed directly on the subject by "bounce cards" attached to the flash unit. That increases the efficiency of the flash and compensates shadows caused by light coming from the ceiling. It's also possible to use one's own palm for that purpose, resulting in warmer tones on the picture, as well as eliminating the need to carry additional accessories.

Which Flash Should I Buy?
If all you'll ever use the flash with is your Coolpix, fancy features such as flashtube zoom, repeating flash, rear sync, red-eye reduction and autofocus assist, and so on, can't be invoked from the Coolpix so are features you're paying for that you can't use. In general, a simple flash capable of TTL and/or Automatic mode is about all you need. Nikon has just introduced just such a flash, the SB-30, and of the current Nikon offerings, it probably is the most suitable if all you'll ever use it on is a Coolpix. The other flashes in the Nikon lineup that make sense with a Coolpix are the SB-50DX, mainly due to its ability to be used wirelessly, and the SB-22s, which is a basic flash with more power than the SB-30.

Wireless
Most Coolpix models can trigger external flash units wirelessly (the SB-50DX or SB-80DX being the models of choice, with their built-in wireless controllers). That's because flash units emit a significant pulse of infrared light, which wireless remote sensors can detect, even in bright situations. One common method of triggering a remote SB-50DX is to put a filter over the internal flash that blocks all but the infrared spectrum (a piece of processed unexposed film works pretty well as a filter). Make sure NOT to block the TTL sensor on the Coolpix, however, as it is still controlling the overall exposure if the remote flash is set to TTL (or Auto Wireless in the case of the SB-50DX). Already have a flash but want to make it wireless? Nikon sells the SU-4 accessory, which has the sensor and a hot shoe to mount your flash on.