Electronic Flash: A Primer

283flash.gif (14317 bytes)Electronic flash photography places light where you want it–when you want it! Flash is controllable and portable. It opens up a new world of photo possibilities. The quality high-speed film now available can lessen the need for flash in some instances, but flash has many useful characteristics regardless of what film is being used.

The color of flash is the same as daylight, so it can be used with your regular films. The burst of light is very brief–often on the order of 1/10,000 of a second or faster. Flash can stop or freeze motion, hence its other name strobe, and it can provide extra light allowing smaller E-stops with more depth of field. It’s very useful in daylight to fill in shadows and enhance colors. Special techniques are possible–such as painting with light.


First, let’s consider the physical placement of your flash. The most common position is on the hot shoe of the camera, which is on top of the prism housing. Unfortunately, this is also the worst possible position. From here, the light travels straight out and back, creating a very flat, harsh, and unflattering look. “Red-eye” is likely. (The red is actually the blood in the back of your eye revealed. This fact makes good party trivia.)

Moving the flash off the camera to the side, even by a few inches, provides a dramatic improvement. Now the light travels at an angle to the lens, which lends shadows to the subject, yielding a more rounded, flattering appearance. “Red-eye” is reduced. An inexpensive L-bracket is used to hold the flash to the side, but you may need an extension cord to reach the camera.


Originally, all flashes were manual in operation. That is, depending on the power of the flash, the distance from the subject, and the film speed, you had to figure the proper f-stop to use. If you moved a few feet, you had to recalculate a new f-stop. In the 1960’s, Honeywell pioneered the automatic flash. This was quite an improvement, for now as you moved around, the flash automatically provided the proper amount of light. This was accomplished by adding a sensor to the flash unit. As light travels to the subject and bounces back toward the flash, the sensor measures the light and quenches the flash when the subject has received enough exposure. You can think of this action as a sort of radar, one which is usually quite accurate. Automatic flashes are highly recommended. Most modern flashes have three or four different automatic ranges, allowing different f-stops and working distances. They can also be placed into manual mode for certain effects.

The next development in flash technology was the thyristor circuit. Inside a flash is a large capacitor (electrical storage device) which is charged to a high voltage by the battery. When you take a picture, the capacitor discharges the stored electricity across the bulb, producing a burst of light. It’s like a car in which the coil and condenser charge up to fire the spark plug. In early automatic flashes, when the sensor quenched the flash, any unused electricity was wasted. This meant the flash had to charge up from zero for each photo. With a thyristor, however, any unused current is saved and applied toward the next shot. This means quicker recycling times, especially when the subject is close. A good example of an energy-saving thyristor flash is the popular Vivitar 283. This versatile flash has good power at a cost of about $100 and can be used with almost any camera.

As cameras have evolved, so have flashes. The most popular flashes are now called dedicated. This means they’re dedicated to a certain camera brand and/or to certain models of a certain brand. A dedicated flash can offer several advanced features, giving you the ultimate in control and creativity. However, they’re expensive and take extra effort to understand. (A dedicated flash can easily cost $200 to $300.) If you want to move a dedicated flash off the camera, you’ll need a special extension cord to do it. These cords are more expensive and harder to find than the simple PC cords for a non-dedicated unit. Perhaps the best reason to own a dedicated flash is its ease of use in fill-flash situations. In close-up and macro work, a dedicated flash is pretty awesome!


Flash power is measured by a term called a guide number. The higher the guide number, the more powerful the flash. As flashes increase in power, their weight and cost increase, too. Most flashes use four AA batteries. Flashes put a heavy strain on batteries, so buy only alkaline types. For even more economy, use rechargeable nicad batteries, and always have an extra set of batteries in your bag.

A common problem for all of us is putting the flash away and forgetting to turn it off. By the next day, the batteries will be completely dead. With fresh batteries, a flash typically recycles in six to eight seconds. A ready-lighton the flash tells you when the flash is recycled. However, some ready lights come on too soon, so–if possible–wait an extra few seconds to be sure the flash is fully recharged. As batteries age, the recycle time becomes very long. You can buy special sealed lead-acid (gel-cel) rechargeable batteries which feature hundreds of flashes with very fast recycle times. The disadvantage is the extra hassle of carrying the battery on your belt or shoulder.


1.) Synchronization

In order for the flash to go off at the right time during the exposure, it must synchronize properly with the camera. This sync speed is usually marked in red on the shutter speed dial. A typical sync speed is 1/60 or 1/125 of a second. Newer electronic cameras may have even higher sync speeds. You must never use a shutter speed faster than your sync speed or only part of your photograph will be exposed. But you can use any speed slower than sync speed. Older cameras often had a choice of two sockets into which you could plug the flash cord. For electronic flash, you must always use the X socket. Never use M or FP which were designed for flash-bulbs.

2.) Film speed

Although a flash has a certain power, the use of faster films makes the flash effectively more powerful. For instance, a certain flash with ISO 100 film may reach out only to fifteen feet. But by using a film four times faster (ISO 400), the effective range is doubled to thirty feet. The flash is still putting out the same amount of light, but the faster film records the flash out farther.

3.) Flash distance

One important aspect of flash photography is frequently the most confusing. For you mathematical types, flash falls off inversely as the square. In plain language, this means, if you double the flash distance, the power is now only 1/2 as great. If you triple the distance, the flash is 1/9 as strong. In other words, if you double the distance, you lose two f-stops!

It’s beyond the scope of this article to discuss specific instructions, but, in general, if you use an auto flash such as the Vivitar 283, do this: Set the dial to the film speed. Next, determine what the farthest distance between you and your subject is likely to be. For example, let’s assume my subject will always be within twelve feet. I look at the dial and see the Blue Auto range is good up to fifteen feet. The Blue range corresponds to f-8 on the dial, so I set my lens to f-8. My shutter is set to the proper sync speed. Now, as long as my subject stays at fifteen feet or closer, I can fire away. The flash will automatically adjust for varying distances.

Now, let’s say my subject moves out farther–to about twenty feet. I look back at the dial and see the Red range is good to thirty feet. But the Red range calls for f-4 on my lens. So, I reset the lens to f-4. Now I can take photos anywhere out to thirty feet. The trade-off, of course, is that at f-4, I have much less depth of field than I did at f-8. This means I must focus more accurately. (Note: A dedicated flash will do all of the above for you automatically!)

Remember, as your subject moves farther away, you must do one of the following: open up to a wider f-stop, use a faster film, or use a more powerful flash.

4.) Subject

Some flashes feature a colored indicator light which tells you if you have enough flash for a given subject without actually taking a photo. You just push the open flash button. If the light comes on, you’re all set. If the light doesn’t come on, try a different range and retest. This is a useful feature to look for in your equipment.

5.) Lens

You must be aware of how lens choice can affect flash results. The light from a flash spreads out as it travels. For a normal 50mm lens, this is no problem. Even for a moderate wide-angle such as 35mm, the flash spread will be sufficient. But with 28mm or 24mm, the lens may be seeing such a wide area that the flash can’t cover it from corner to corner. Some flashes come with zoom heads or auxiliary panels to modify this spread of light.


A popular selling point of flashes is the ability to bounce the light. However, in real life, bouncing is a mixed blessing. The benefit of bouncing the flash is a softening and spreading of the light. But, in bouncing illumination off the ceiling, you lose considerable effective flash power (about two stops). You can also pick up a color cast, depending on the color of the ceiling. Plus, you create annoying shadows in the eyes–which I call cesspools–since the light is falling on the head from above. A better method is to attach a diffusing device of some sort to the flash. Several types are available. They spread the light, making it softer, and cost only about one f-stop. Even a plain white hankie taped over the flash head can soften the light nicely.


When you store your flash for any length of time, remove the batteries. It’s also a good idea to maintain the flash capacitor. If a flash isn’t used for several weeks, the capacitor loses its ability to hold a charge effectively. To correct this, you must periodically reform the capacitor: Set the flash for full-power manual operation. With good batteries installed, turn the unit on and wait four or five minutes. Then fire the flash six to eight times, waiting about twenty seconds between each burst. Finally, with the flash fully charged, turn it off and put it away. Do this about once a month. Nicad batteries require special care and feeding. Just follow the instructions that come with them.

A FINAL WORD ABOUT FLASH PHOTOGRAPHY: Don’t be afraid to experiment!

by Steve Traudt

All written content (and most images) in these articles are copyrighted by the authors. Copyrighted material from Apogee Photo Mag should not be used elsewhere without seeking the authors permission.

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