I doubt if there are many wildlife photographers who are not familiar with the Visual Echoes (aka BetterBeamer) tele-flash system, and our offices has promoted and sold these tele-flashes for years. I mention this again, now, however, because Canon has introduced a new electronic flash, the 580EX, to either supplement or replace the 550EXs that have been available for years. The new flash has a bit higher guide number, but more significantly, it also has some easier controls, particularly for obtaining High-Speed Flash Synch, which is now done by just a push of a button. The flash is a bit narrower, too, so that an older version of the VE Tele-Flash, while it will mount, won't be as snug a fit as the new version, the FX3.
On our most recent Kenya trip I had an opportunity to field-test the FX3 for the first time, and I was so impressed I felt it was worth a special mention as a monthly tip. The 'arms' of the tele-flash are precisely molded to fit this smaller flash, and one end of the velcro strap used to anchor the unit to the flash head is permanently glued to the flash arm. This makes for a quick, snug fit where there's no fumbling to find the elastic band used for securing the flash arms. In a safari vehicle, under duress and time constraints, that's a very, very handy feature.
To be honest, I haven't done a side-by-side comparison between the old 550 flash and the new 580, and to be perfectly candid I bought one simply because it is the latest toy, and I rightly or wrongly assumed that it would be better. I have no complaints about the flash and, indeed, I do appreciate the more compact size and the high-speed flash synch button, but I don't know if everyone needs to run out and buy one. Supposedly it works better with digital cameras than the 550 did, but that's grapevine stories, and I haven't tested that for myself. I produced fine work with the 550, thanks.
If you do have the 580EX, it makes perfect sense to invest in the the FX3 tele-flash system. It's a great addition to a great flash. If you are interested, we sell them here at our office so please contact us.
By the way, what is high-speed flash synch? Normally, electronic flashes fire at a maximum fast shutter speed which may be 1/180th, 1/200th, 1/250th, or 1/300th, depending upon the camera model you are using. The flashes will fire at slower shutter speeds -- anything less than 1/180th or 1/300th, etc., but there is a normal limit to how fast a shutter speed can be set. This is because the focal plane shutter must be fully open when the flash fires - and it will not be at faster shutter speeds as the second curtain of the flash will already be closing before the first curtain is fully open - resulting in only a partial section of the frame being exposed. Minimum 'fast' or maximum synch speeds, whatever term you wish to use, insures that the entire frame will be 'flashed.'
With High Speed Flash Synch the flash illuminates the entire frame by emitting several pulses of flash during the exposure. Essentially each pulse or bust of light illuminates one section of the frame while it is revealed. With extremely fast shutter speeds, the 'slit' or opening between the first curtain and the second is extremely narrow, and a flash may have to pulse several bursts to illuminate the entire frame. Remember, we're talking fast shutter speeds, so the flash is doing this in the space of a shutter speed of 1/500th or 1/1,000th or faster! Because a flash would need to recycle (replenish its energy) between bursts if all of its power was drained, a flash won't dump all of its energy in the first of a series of pulses or bursts whnen in High Speed Flash Synch. Instead, the flash will ratio out the power so that there's enough energy, or power, so that each pulse or burst is equal, insuring a uniform exposure across the frame.
To do this, when you are on HSFS (high speed flash synch) the Guide Number of the flash drops, in effect making the flash weaker -- while providing more pulses per second. It would make sense, then, that fewer pulses would be required for shutter speeds just a bit faster than the 'normal' synch, and more pulses for shutter speeds much faster than the normal. Accordingly, then, the GN will decrease to accomplish this.
This explanation is not a tedious exercise in flash theory. Too often I've seen people use flash, even with a tele-flash attached, attempting to provide fill-light or even stop-action lighting, when the flash-to-subject distance was too great or the aperture was too small for the effective GN. Many photographers simply never look at the GN chart posted for various shutter speeds with HSFS, or if they do, they don't understand the implications.
To sum this up, if you use HSFS, your flash, even with a tele-flash, will not reach as far as it will when you are not using HSFS because of the repeated bursts, or flash pulses, required during the faster shutter speeds. Fortunately, with a digital camera you should be able to see the results of flash fill either on the LCD monitor or via the histogram -- but if the ambient lighting conditions are too bright that can be impossible.
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