I was just thinking about this problem and was wondering if anyone knew if/how to use a competing flash unit (EX or SB series) on a Nikon or Canon (respectively) camera. I would assume a lot of the brand-specific flash features may not work (wireless for example) but would the manual flash-on-the-hotshoe work fine?
If it is possible, what features are or are not available?
I was thinking about how, for example, in a teaching situation, you could use a single flash on both brands of camera.
Yes, it will work, or at least, it's worked in the case I've tried (canon flash on a nikon body). You're right that the specific TTL metering and the like doesn't work, but the flash definitely triggers.
I remember it distinctly, because both of my flashes went down while shooting a large wedding and the primary had a spare canon flash. She lent it to me, and it worked-- which produced a camera that looked exceedingly strange (what with both canon and nikon working together), but it worked in manual mode.
Yes, you can use either brand on the other one's hotshoe, and the flash will fire in sync with the exposure being made. But that's the only function you will have. No i-TTL/e-TTL, no high-speed sync (FP), no menu commanding of the flash, no flash exposure compensation, no wake-up from sleep, no 2nd curtain with a Nikon flash on a Canon camera, no matching the zoom to the lens's focal length—anything that requires communication between the flash and the camera body other than the "fire!" signal won't be communicated.
If you look at the camera's hotshoe and the flash's foot, you'll see why.
Nearly every camera manufacturer follows the ISO standard for flash hotshoes (for a while Sony didn't, using the old Minolta iISO hotshoe, but as of the NEX6, they've moved to the ISO-compliant (sorta) multi-interface hotshoe). The ISO standards for flash feet and camera hotshoes give the physical dimensions of the foot and shoe, and specify that the rails on the shoe are ground, and that the contact in the center of the "square" of the foot/shoe is the sync signal.
Everything else is proprietary. Canon and Nikon have their non-sync contacts/pins placed in different areas, so if the flash is seated correctly on the hotshoe, there is no electrical contact and no communication.
However. The four-thirds, micro four-thirds, Fuji X, and Canon hotshoe contacts all use identical placement (although Canon has an additional signal not found on the other two), so if you mix brands among these three, there is the possibility of cross-talk. And since every brand uses a completely different signaling protocol, there could be some errors and possible damage (although the risk is small), so if you're very paranoid, taping over contacts or removing pins might be advisable. I pulled the TTL pins (completely reversible) on an SB-26 to use it on my Canon hotshoes.
On the upside, however, this similar placement also means you can use Canon TTL cables for full TTL function with OEM gear (i.e., you can use a micro four-thirds flash with a micro four-thirds camera over a Canon TTL cable and have full function with TTL and high-speed sync); but this only works with passive cables simply doing signal pass-through. It does not work with TTL-capable radio triggers which may do some form of signal manipulation. However, a newer version of the Fuji X hotshoe now supplies power to accessory flashes with an additional contact the Canon hotshoe doesn't have, so Canon TTL cables will not work with those flashes (such as the EF-X8), as they have no other power source.
While Nikon and Pentax have separate pin arrangements, oddly, the wake-up signal is identical both contact-placement and electronic signal-wise so something like a for-Nikon Yongnuo RF-603II can actually wake up Pentax flashes, but again, there's no TTL/HSS cross-brand with Nikon gear on Pentax.
Sync voltages, if you are using digital-era flash models, should not be an issue. All the digital-era flashes tend to have sync voltages of <10V, and most Canon/Nikon hotshoes have a limit of 250V, while mirrorless cameras are guesstimated to have limits around 20V. The 6V limit you often seen in web references are for the first generation of Canon dSLRs. If you have a Canon camera model that was made after the original dRebel (300D), the limit is 250V.
If you really need cross-brand TTL/HSS compatibility with legacy flashes, you may want to consider the Cactus's X-TTL triggering system.
The only brand which uses a physically different connector is Sony since they inherited it from Konica-Minolta. All other brands have the same connector and you can mount whichever flash fits.
The basic sync always works, meaning it will trigger at the right moment. Sophisticated metering and sync may not depending on the camera and flash combination. If you use the flash controls on the camera, many models will grey-out options which are not supported, for example rear-sync or manual-flash. You can still set manual-power and FC directly on the flash itself, of course it takes more work to figure out what is needed there.
One word of caution, you should ensure that the trigger voltage for the flash doesn't exceed what your camera specifies. A pretty complete list can be found on this site, though it is more Canon oriented, of flash trigger voltages to use as a reference.
I have this old 630AF Achiever flash. The box reads "fully dedicated for minolta and nikon autofocus cameras" but I use it on my Canon dslr and it seems to work just fine. I have been using it on a tripod in Aperture value AV mode.
As others said, it will work. In addition, if the flash has an auto-thyristor mode for metering (the flash meters with a sensor in the body), that will work, independent of a body. It will even work off camera with some other trigger mechanism (optical, wireless, etc)
In general Yes. The strobist, David Hobby, recommended a fairly old Nikon SB flash for all of his followers, and the prices of them instantly went up on eBay and craigslist.
http://strobist.blogspot.com/2006/05/for-few-dollars-more-nikon-sb-26.html
