Photo Safaris - Picking A Flash Unit



				Ultimate Antarctica January 5–February 1, 2008

Whenever I talk about or teach flash photography, I worry about creating a Frankenstein monster. Dr. Frankenstein hoped to produce a noble creation, but created a monster instead. I worry that my sincere efforts to educate people on the proper use of flash will, instead, have folks using flash at inappropriate times or in ineffective ways. I try to stress that I use flash only when:

ambient light is too low for using natural light alone
natural light is contrasty and unattractive
Im trying to stop action that traditional camera shutter speeds cannot

Nonetheless, even when restricting my flash work to these three primary uses electronic flash still plays an important role in much of my photography.

If you were choosing just one flash unit for all of your photographic work, Id strongly recommend buying a flash that is offered by your cameras manufacturer.

Id suggest buying the top of the line hot-shoe mounted flash offered in that system, assuming that unit would offer the most versatility in terms of flash modes and power ratios. Ill cover why in a second. Secondary manufacturers, like Vivitar and Sunpak, offer great flash units, but these should be considered primarily as backup flashes or accessory units for special purposes.

Im most familiar with the Canon and Nikon product lines, and Ill restrict most of my comments to these systems. In my experience, while Minolta may make a great flash, Ive not found using their flash to be easy. The operating system is quite different from either Nikon or Canon and figuring out what buttons to push is certainly not intuitive. If youre a Minolta shooter, youll have to master this, of course. But dont be surprised if your fellow photographers — if they are Nikon or Canon shooters — are of little help if you should need it.

The top of the line hot-shoe flashes offered by Canon and Nikon have several flash modes, including full TTL, automatic mode and manual. Canons two top flash units are the 540EZ and the 550EX. The 540 is designed for the 1N series (and lesser models), and the 550EX for the new EOS3 and 1V cameras. Nikons top flash is presently the SB28, but the discontinued SB26 is a far better flash. All of these flashes also offer a stroboscopic mode, where the flashes fire several short bursts during the duration of an exposure, but Ive never used this feature with either unit.


Back of a Nikon SB flash. A good flash unit should provide controls for over- or underexposing the flash exposure, as well as manual power ratio capabilities.

Although the Nikon SB28 is currently Nikons top flash, Ive never liked the unit. The flashs push button controls are just too small, and to operate the flash Ive found myself using the tip of a pencil or pen to depress the tiny, recessed buttons. Most flashes, including the SB28, have a test flash button that will fire the flash when pressed, and Ive found even using this button to be difficult!

A better choice, by far, is the Nikon SB26. This flash has all the features of the SB28 (those features that count, at least), but the SB26 also has larger push button controls that are easy to use. The SB26 has a built-in slave sensor (for manual mode) that fires the flash when another flash fires. Perhaps Nikons product people felt this accessory was unnecessary, infrequently used or misunderstood. I found the slave feature to be invaluable, especially with hummingbird set ups involving several flash units. Why did Nikon discontinue this flash? I dont know, but Id recommend seeking out a used SB26 in lieu of buying a new SB28!

With Canon, there are really just two choices for the top flashes — the 540EZ or 550EX. Either unit offers complete control over the TTL lighting ratio as well as varying power ratios for manual flash. Other flashes lack these features, and the more you use flash, the more youll want to control its use. The 540 and the 550 allow you to do just that.

Both the Nikon and the Canon flash units offer an automatic mode. In this mode, the flash exposure is not determined by light passing through the lens (TTL), but instead by a sensor built into the flash that reads the light reflected off the subject. This sensor may or may not read the subject or the area covered by your lens, and over- or underexposures can result. Ive used the automatic mode most effectively for off-camera flash when Ive painted scenes with a flash held some distance from the camera. To give you some idea of its usefulness, Ive only done so a few times in my career.

Several manufacturers, Nikon and Canon included, make ring flashes for macro work. Ring flashes attach directly to the front of the camera lens by screwing into the filter threads of the lens. Better ring flashes have the capacity to control and vary the flash output for either side of the lens to produce a Key and a Fill light, and to turn off one side of the ring flash. Ring flashes work great for some macro work, especially for flower close-ups, but Ive found their use rather limited.

Typically, ring flashes have a low Guide Number, requiring the flash to be placed fairly close to the subject if small apertures are being used. In wildlife work, close working distances can be a problem, as can the reflected ring of light that appears in an animals eyes or on any reflective surface. Bright circular rings are not natural, and their appearance is usually unsightly. Id suggest buying a ring flash only if you plan on doing a lot of close-up macro work involving subjects that do not have highly reflective surfaces. If youre planning on becoming the definitive frog photographer, skip the ring flash.

I mentioned Guide Number, a term you may or may not be familiar with. The Guide Number is, essentially, the flashs power rating. A flash with a high guide number will produce more light than a flash with a low guide number. This means, at any given distance, youll be using a smaller f-stop with a high Guide Number flash than you would with a low GN unit. At any given f-stop youll have a greater flash-to-subject distance with the high GN flash than with the low. Nikon and Canons top flashes have GNs that are rated about 120 to 130 (in feet), but these GNs are rated for indoor use. Indoors, walls and ceilings contain the light, bouncing it back towards the subject, and the manufacturers GN rating will usually be higher than what youll experience outdoors. Because light that does not strike the subject (or a light meter measuring the output) is lost, the GN will almost always be lower than the official rating. In some flashes, this can be by as much as a stop of light!


	Inexpensive multi-PC terminals will allow you to attach several flash units together. In this example, the flashes are connected to a slave unit that will fire the units connected via the terminal.

As I said earlier, you should purchase your primary flash from your cameras manufacturer. With that flash, youll enjoy all the features your system allows. With the flashes mentioned (Nikons SBs, Canons 540 and 550), theres an active interface between camera, lens and flash. The flash will know what lens aperture is set and what lens is in use. All of the above flashes have automatic Fresnel lens settings that concentrate or broaden the flashs beam to match the angle of view of the lens being used, generally between 24mm and 85mm or 105mm. None of these flashes can focus a beam tighter for lenses longer than 85mm (with Nikon) or 105mm (with Canon), but with a tele-flash extender the flash beam concentrates even tighter, approximately that for a 300mms focal length.

Of course, you can use lenses longer than 85mm or 105mm without a tele-flash extender, and lenses longer than 300mm when used with a tele-flash extender. In either case the flash coverage will be broader than the lens coverage. In effect, when longer lenses are used, light is wasted since the longer lenses cover a much smaller area inside the area covered by the flash.

Youll use your primary flash for most of your flash photography. One TTL flash will satisfy all your needs:

basic fill lighting
tele-flash techniques using a tele-flash extender
full flash at night or with macro subjects

If you plan on using a second flash, your purchasing options broaden considerably, and youll have to ask yourself some serious questions about that second flashs function. One problem with a single flash, especially if it is the sole or primary light source, is that the flash can produce harsh shadows and contrasty lighting. A second flash can soften the shadows produced by the first flash, thereby reducing contrast. It is easiest to use a second flash on TTL and to let the camera and flash operating systems handle the exposure, but here you may find some problems. Exactly what they may be will depend upon your system.

For example, some flash units allow you to change the power ratios in a dual TTL flash setup. You designate one flash as a Key light, and a second as the Fill. Think of the Key light as the main light, or primary light source. The Key light will produce shadows, which the Fill light will reduce, or eliminate, filling in the light. You can have two light sources of equal intensity (and you can consider them as either two Keys or two Fills) since the shadows produced by each will be filled in by the other, but this lighting often looks contrived. Two shadows, however faint, are usually visible, often on either side of the subject. In the natural world, theres usually just one shadow cast.

Some TTL systems do not have the capability of adjusting power ratios for Key and Fill effects. Achieving this Key and Fill look may require you to do one of several things:

place the Fill flash further from the subject
cover the Fill flashs head with some type of diffusion material (a tissue or wax paper will do)
zoom the flash head to a wide-angle setting so that the light produced from that flash head is more widely dispersed

Buy a second flash in your system to insure compatibility. Some of the newest flash units offered by Canon and Nikon (Minolta had this feature for years) incorporate wireless TTL, while older units utilized some type of hard-wiring system between units. The wireless TTL systems have the obvious advantage of — duh — no messy wires, but may present the problem of having the flashes arranged so that theyre in view of one another. With wired systems, the flash units can be hidden from one another.

You may not, however, require TTL capability for your second flash or for accessory flashes and, if thats the case, seriously consider the off-brand flashes. This summer I will be experimenting with a full TTL multi-flash setup with Canons 550EX flash units for hummingbirds. In the past Ive used manual units or inexpensive auto-flashes with a manual mode, or even expensive SB24s, 25s and 26s on manual mode for this type of photography. On manual mode, I can select the power ratio I need, either for the desired f-stop or, most importantly, for the flash duration required for the subject. At full power, the flash duration of most flash units is too slow (meaning it is too long) to be of any use in stopping action. That duration may be as slow as 1/1000^th of a second or longer. For hummingbirds, flash durations of 1/4000^th of a second or 1/8000^th of a second are necessary to stop a hummers rapidly beating wings. Youll get these shorter flash durations by dialing down the power ratio to a 1/8^th, 1/16^th or 1/32^nd power ratio.

While TTL flash can emit short bursts of light as fast as 1/50000^th of a second, it is difficult (perhaps impossible) to predict or control exactly how short the flash duration will be, since the flash metering system determines the length of the flash exposure. If a subject is close to the flash, the flash duration is brief. Likewise, if the aperture is large (small f-number), or if the flash zoom head is zoomed to a longer focal length, flash durations will be shorter than with small apertures and shorter focal lengths. However, there is no way to insure an exact speed and, if you need a fast flash duration, you cannot be sure youre getting exactly what you need.


Relatively inexpensive flashes like Sunpak or Vivitar can be used in conjunction with your brand name flash for multiple flash effects. In this example, three flash units are attached to one slave unit.

With manual mode, changing (sometimes referred to as dialing down) the flash power ratio shortens the flash duration. These changes are constant; there is no guesswork involved. The full power setting provides the longest flash duration and the minimum power setting provides the shortest flash duration. Between the two extremes is a fixed range of flash durations, perhaps ranging from 1/1000^th, 1/1500^th, 1/2500^th, 1/4000^th, 1/8000^th, 1/16000^th, etc. At a low power setting of 1/64^th power or 1/128^th power, the flash duration may be as short as 1/30000^th of a second!

Of course, as you decrease the power ratio, youll also lower the Guide Number, or the power of the flash. At lower GNs youll have to use larger apertures (small f-numbers) at any given distance or youll have to place the flash or flashes closer to your subject to use small apertures than would be required with larger GN flashes. But this works, and it is what Ive done for years to film hummingbirds and other birds in flight, as well as jumping frogs, running basilisk lizards, striking rattlesnakes, etc.

Ive guessed what flash duration Id need, set my manual flash unit for the power ratio that provided that flash duration and placed my flashes at the distance necessary for that aperture. Ive used several different flash systems for this — from inexpensive automatic/manual Sunpaks and Vivitars, to more expensive Metz automatic/manual units and very expensive custom high-speed systems. As I said earlier, Ive even used my Nikon SB units on manual mode in this fashion, but that seems like folly when you consider the price of the units. The same thing can be accomplished much less expensively with secondary market auto/manual units.

However, if you use manual mode, youll have to determine the flash exposure. In TTL mode, remember, you do not. Instead, you simply set the aperture and — provided the subject is within range of the flash the exposure should be correct. While this is great, there is one cost — you give up complete control over the flash duration. In manual mode you have total control over your flash exposure and the flash duration, but youll have to determine the correct exposure. To do so, you can use the Guide Number formula, your units flash-to-subject distance scale (usually located on the back of the flash) or a flash meter. The easiest to use is the flash meter and thats what I do. My meter is the Minolta Flash Meter IVF. It works for flash metering, as well as for ambient or natural light.

If youre shopping for a completely new system, seriously consider any system that offers high-speed flash synch with TTL metering. Normally, a flash exposure can only be made up to a particular maximum flash synch speed (up to 1/250^th or 1/300^th of a second with 35mm SLR cameras). Beyond that shutter speed, if a flash is turned on, the camera will default to the fastest flash synch speed if the flash is hot-shoe mounted. Thats not the case if the flash is connected to the camera by a power cord (PC), as the camera may not default to the fastest flash synch speed and the flash may be out of synch.

With high-speed flash synch, you can use shutter speeds faster than the normal fastest synch speed. This can be very useful when doing TTL flash fill outdoors. Normally, one of the limitations of using flash fill is being restricted to shutter speeds of 1/250^th of a second or slower. If you need a faster shutter speed to stop your subjects motion for an ambient light exposure, youre out of luck if you also wish to use flash for filling in harsh ambient light shadows.


	Flash is invaluable for difficult lighting situations. TTL or manual flash would work for this barred owl.

If you do use flash, and the flash synch speed is still too slow for the subjects movements, youll get a weird optical effect called a ghost image. This typically blurred or double image results when the flash captures or freezes a brief instant during the time the shutter is open. Since the shutter speed was too slow to stop the subject the natural light exposure is blurred, while the flash exposure is frozen. This frozen flash image registers on film, too, often combining to creating some type of blurred, unattractive, ghosted image.

A fast TTL flash synch speed allows you to use the fast shutter speeds sometimes necessary for action shots while still enjoying flash fill. In most camera systems high-speed flash synch is not an option, but the latest camera systems are incorporating this useful feature. Minolta (I believe) and Canons EOS3 and 1V do so, and Im sure Nikon will soon follow suit. Nikon offers high-speed flash synch, but only in a manual mode. When I shot Nikon I found this to be cumbersome and impractical, and I didnt use this feature.

Unfortunately, to achieve a fast flash synch speed the flashs Guide Number drops considerably, so working distances or small apertures are compromised. Personally, though, I havent found this to be much of a problem since Im usually using this feature with my longer telephotos when my apertures are rarely smaller than f/8. With high-speed flash synch Im only interested in flash fill (meaning a flash exposure equivalent to f/5.6 or less if my lens is set at f/8), so low GNs arent that big a problem. Besides, Im usually using a tele-flash extender that effectively doubles or triples the flashs GN.

What should you be looking for in your flash system?

Perhaps it is nothing more than a straightforward TTL system with the ability to change the flash compensation.
If youre filming birds, mammals, or even active people, where fast shutter speeds and contrasty light is involved, consider a high-speed TTL flash synch system.
If youre doing multiple flash setups, seriously consider whether an expensive TTL system is required.
If youre using more than two flashes, you might be better off with a less expensive manual-automatic system where, on manual mode, you have a choice of power ratios.
If youre into flowers and other macro subjects, provided they lack highly reflective surfaces (like eyes or smooth, wet skin), consider a ring flash.

For the record, I use a 550EX flash for my TTL, high-speed flash synch and tele-flash TTL work. For hummingbirds and field setups requiring potentially fast flash durations I use several different systems. All work, and my choice depends on how much weight I wish to carry, how large a working area Im using, or how many flash units I have going elsewhere. For these setups Ill use either a Metz 60T flash system, a Sunpak 522 flash system, a Sunpak 383 system, a Vivitar 385 system or even a Nikon SB system set to the manual flash modes. Each system is comprised of four flash units of the same type, so you see I have A LOT of flash units! But for nine years Mary and I conducted hummingbird shoots where we supplied the flash units for our participants, and we needed several systems! If I had to pick one, as you probably will, Id look at the unit that offers the most for the money youre willing to spend. Remember, the higher the GN, the more powerful and, ultimately, the more versatile the flash will be. All of the above systems have both an automatic and a manual mode, but I only use the manual mode settings.

There are some new flash systems now available, and in the coming months I plan on testing some of these. If theyre worth mentioning, Ill let you know in a later issue.



	Joseph Van Os Photo Safaris, Inc. P.O. Box 655, Vashon Island, Washington USA 98070 Phone: (206) 463-5383 Fax: (206) 463-5484 Email: info@photosafaris.com Copyright © 2008, Joseph Van Os Photo Safaris, Inc.