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Notes on the Sigma EF-500 Super flash unit.

Copyright © 2002 Jim Strutz, NK Guy.

For a long time there were no really serious alternatives to Canon products when it came to E-TTL compatible EOS flash units. However, with the EF-500 Super and the EF-500 Super DG, Sigma have very interesting contenders on the market.

Note that this page deals solely with the Sigma EF-500 DG Super, and not other confusingly named Sigma flash products (eg: EF-500 ST, EF-430 Super or EF-430 ST) It also deals with the version of the flash unit designed to work with Canon EOS cameras only. The EF-500 DG Super is also available in versions compatible with Nikon, Minolta, Pentax and Sigma cameras, and there are differences in the way the other versions of this flash unit operate. (Sigma refer to the one compatible with Canon EOS cameras as the "EO" model)

Be careful when buying one of these units - you don’t want to get a flash unit that isn’t compatible with your camera. You also don’t want to confuse the ST and Super models - of the two the “Super” models are the better type. You probably also want to get the Sigma EF-500 DG Super model, and not the earlier EF-500 Super, since the DG model is supposed to have improved compatibility with Canon digital EOS cameras.

Finally, keep in mind that this page is just a brief set of notes, not a full review. It was partially written by NK Guy based on information from Jim Strutz, who has used and directly compared the Sigma EF-500 Super and the Canon 550EX. If you’re unfamiliar with some of the technical terminology used in this document please refer to my flash photography with EOS cameras article, linked at the bottom of this page.

Reverse engineering.

Sigma Photographic, a Japanese company, have long been known for their third-party lenses, which rely on reverse-engineering of Canon’s lens mount protocols. In other words Sigma buy Canon cameras and lenses, hook them up to computers and figure out how they talk to each other. Tamron and Tokina are two other manufacturers which sell third-party lenses, all likely reverse-engineered in this way.

This reverse engineering process is needed since Canon is unwilling to license their protocols to third party manufacturers. (there are often rumours that Tamron obtained a licence for Canon technology, but this has been refuted publicly by Canon USA’s Chuck Westfall) But there is a drawback of reverse engineering to the consumer. Sigma may indeed be able to figure out how their products can work flawlessly with all existing Canon products, but Canon is perfectly able to alter its future products in such a fashion that the older third party items no longer function correctly. Whether inadvertently or deliberately, this happened most recently with the introduction of the EOS Elan 7/30/33/7, which does not work with certain older Sigma lenses and with older Metz flash adapters. Note that to their credit Sigma will reprogram many of their lenses for free so that the older lenses would work with the newer camera, but not all of their older products can be so upgraded. Anyway. Sigma have similarly reverse-engineered Canon’s flash protocols and produced the EF-500 Super and EF-500 DG Super flash units.

So why would you want a third-party flash unit? Well, there are two basic reasons - they may be cheaper or they may offer features which Canon does not. In the case of the Sigma EF-500 DG Super the primary draw is the price - when it was first released it cost roughly half the price of the comparable Canon Speedlite 550EX. Two flash units for the price of one - it’s a very attractive offer. This price differential is less pronounced now that the Canon 580EX has driven down the price of the 550EX, but it’s still a factor.

Sigma/Canon similarities.

As noted, the Sigma EF-500 DG Super is very similar to the top of the line Canon Speedlite 550EX. Both devices are shoe-mounted battery-operated portable flash units with full support for Canon type A cameras - E-TTL, FP mode flash and so on. They can also operate in plain TTL mode for compatibility with older type B cameras, but neither unit supports A-TTL flash.

In addition both products feature motorized zoom heads with tilt and swivel, full manual controls, optionally backlit rear-panel LCDs for the display of useful information, AF assist lights, manual controls for flash exposure compensation, support for second-curtain sync, stroboscopic flash, modelling flash and so on. Sigma have even figured out Canon’s wireless flash system, so the EF-500 DG Super can be used as either a master or a slave unit with wireless E-TTL.

In short, the EF-500 DG Super is almost identical to the 550EX in terms of its feature list.

Sigma/Canon differences:

Almost, but not quite. Here are the key differences between the two products.

  1. The 550EX has custom functions; the EF-500 DG Super does not. The EF-500 DG Super therefore does not provide some of the same options as its Canon counterpart.

    CF 1 disables the auto cancellation of flash exposure bracketing (FEB) at the end of the three FEB shots. This way you can use FEB for the whole roll if you want, without having to reset it every time.

    CF 2 changes the sequence of FEB to under, normal and over-exposures instead of having normal first.

    CF 3 disables E-TTL and reverts to straight TTL. This is a very useful option when working with optical slave flash units, which can be triggered inadvertently by the E-TTL preflash.

    CFs 4 and 5 control the amount of time that elapses before save-energy (SE) mode kicks in while in wireless mode. CF 4 controls whether SE is engaged after 1 hour or 10 minutes when the flash is in slave mode. CF 5 controls the length of time during which the master flash can wake up the slave flash - either 1 hour or 8 hours.

    CF 6 enables or disables the 550EX’s AF assist light.

  2. The 550EX has an AF assist light that covers a very wide area - all 45 focus points of the EOS 3 AF system, in fact. There are two caveats to this. First, the light does not cover the upper and lower focus points on the Elan 7/EOS 30/33/7 and second, the light is much brighter in the centre of the coverage area than on the sides.

    The EF-500 Super is much more limited in this regard, as its AF assist light works only with the central focus point on cameras with multiple points. If you select a side AF point then the camera body’s internal AF assist light kicks in instead.

    This isn’t a problem with EOS cameras with red AF assist lights built in such as the Elan II/EOS 50/55 unless the body’s internal AF assist light is blocked by a large lens or lens hood. However it could be an issue when the flash unit is used with bodies such as the Elan 7/EOS 30/33/7 or Rebel 2000/EOS 300 or pro bodies such as the EOS 3 and 1V, all of which lack body-integral red AF assist lights.

    Note that the EOS 5/A2(E) and 10/10S cameras will not activate the AF assist light of any external flash unit, but this is a limitation of the body and not of the flash.

  3. The 550EX does not cancel FP mode (high speed sync) flash unless you deliberately instruct it to. However, the EF-500 Super inconveniently cancels FP flash mode if the shutter speed drops to the camera’s X-sync speed or below. And it won’t re-enable FP mode until you set the shutter speed back up above X-sync.

  4. The 550EX is about 1/4 stop more powerful than the EF-500 Super. (the 550EX has a rated metric guide number (GN) of 55 and the EF-500 Super a rated GN of 50) Which is part of the reason for the faster recycle time (see point 11) of the EF-500 Super.

  5. The 550EX has an interface that’s easier to understand and operate. The EF-500 Super makes do with fewer buttons but has more menu selections to do the same job.

  6. The 550EX motorized flash head zooms out to cover a 24mm lens. The EF-500 Super only covers a 28mm lens. Each flash unit, however, has a built-in flip-out wide diffuser panel that both makers overrate to 17mm coverage. And each flash head can zoom to cover a 105mm lens. (note that the focal lengths and coverage areas mentioned assume the use of a 35mm film camera)

  7. Flash exposure confirmation is a small LED (light) on the 550EX and a blinking indicator on the LCD of the EF-500 Super.

  8. The 550EX has a three position power switch - off, on and SE, the 90 second “save energy” timeout mode. The EF-500 Super only has two positions and is normally in a 90 second power save mode. However, if the Sigma unit is acting as a master or slave in a wireless setup, or is in optical slave mode, it will never shut off.

  9. The EF-500 Super can operate as an optical slave unit. (in this mode the flash unit will trigger in response to any burst of light from another flash) The 550EX cannot. Unfortunately this mode is limited by the fact that you must apparently meter the flash output manually.

  10. Wireless ratio control. The 550EX identifies wireless groups as A, B or C. The EF-500 Super identifies the groups as 1, 2 or 3. Functionally they’re equivalent.

  11. The 550EX has a high voltage socket for using Canon’s Transistor Pack E or their Compact Battery Pack CP-E2. This port is also used by the Turbo, Mini/Megacycler and Jackrabbit batteries for very fast full power recycles. The EF-500 Super has no such high-voltage connector. However it does recycle 25-30% faster than the 550EX while using AA batteries.

  12. Some users have reported compatibility problems with the EF-500 Super’s implementation of wireless E-TTL. The 550EX does not have such problems.

  13. The 550EX works with all Canon digital cameras which support EX series flash units, including the digital point and shoots. Sigma make no claim that the EF-500 Super will work with Canon’s digital point & shoot cameras such as the PowerShot Pro 90, G1 or G2. It doesn’t work correctly with the G1 or G2. Reports are inconsistent as to whether it works with Canon’s first round of second-generation digital SLRs - the 1D, D30 and D60. Apparently it does not work correctly with the EOS 10D. Sigma have announced a DG version of the flash which is digital-compatible (see below).

  14. The 550EX is nicer, has better controls, is solid and reliable, feels sturdier and is pretty well guaranteed to work with all future Canon cameras which support E-TTL. The EF-500 Super lacks a few 550EX features, has some minor incompatibility issues as outlined above (particularly the AF coverage area problem), has a cheaper-looking boxier case, has a poor reputation for reliability and may not work with all future E-TTL capable Canon cameras - but it costs roughly half as much.


It appears that the Sigma unit is also not without certain problems that don’t affect its Canon counterparts.

First, as noted above, is the issue of compatibility with Canon digital cameras. Sigma have announced a new flash unit, the Sigma EF-500 DG Super, which they claim is compatible with EOS digital cameras.

Second, many users have reported inconsistent flash metering with the Sigma that doesn’t happen with Canon products. This is a serious issue, particularly for slide film and digital camera users where exposure latitude is less.

Third, I’ve heard one report of the Sigma not correctly previewing flash ratios when using the modelling light function.

Finally, future compatibility with Canon camera bodies in general is not assured, given Sigma’s track record when it comes to lenses and the like. Canon’s Speedlites, however, basically work on future cameras - the issue of TTL and A-TTL support being dropped on digital cameras aside. While this is true, ask yourself whether or not you’ll get enough use out of the units now with your existing cameras. If you think you will - and the Sigma works well for you - then the cost savings of the Sigma may outweigh future compatibility issues.


If money is no object then you’ll want the Canon Speedlite 550EX since it’s a better flash unit than the Sigma EF-500 Super. Working professionals will probably also want to stick with Canon since the build quality of the 550EX is clearly higher, and the FP mode problem (point 3 above) can result in awkward fumbling for controls and missed photo opportunities.

But remember that for the price of one 550EX you can almost buy two EF-500 Supers and use them in a master-slave wireless combination. That’s a pretty interesting option, especially if you’re operating on a budget and the problems listed above aren’t significant for you.

More information.

Sigma USA have a Web page for this flash unit, but it doesn’t have very much useful information. I wonder when they’ll realize that photographers are relying more and more on the Internet for information related to their purchasing decisions.

Here’s their page on the Sigma EF-500 DG Super.

Sigma Japan have somewhat more information available about the DG version.

Here are the technical specifications for the Canon 550EX flash unit.

This is a very short and not very comprehensive review:

For more information on flash photography using Canon EOS equipment in general, and explanations of the terminology used here, have a look at: