Digital Rebel XT/350D - Flash sync voltage rating

[Doug_Kerr]

Chuck Westfall, Director/Media & Customer Relationship, Canon USA, advises as follows regarding the flash sync circuit of the EOS Digital Rebel XT (EOS 350D):

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The EOS Digital Rebel XT uses a modified version of the EOS 20D's shutter unit. Consequently, acceptable trigger circuit voltage for both cameras is the same, i.e., 250 volts. Except for the original Digital Rebel, all current EOS digital SLRs (i.e., EOS-1Ds Mark II, EOS-1D Mark II, EOS 20D and EOS Digital Rebel XT) generate their X-sync signals electronically rather than mechanically. This is why they have higher acceptable trigger circuit voltage ratings than earlier models like the D30, D60, 10D and original Digital Rebel. These older models cannot be modified to achieve a higher trigger circuit voltage rating, since such a modification would require a different shutter mechanism as well as a complete redesign of the supporting circuitry.
*****

Best regards,

Doug

[John_Vito]

Thanks Doug! That's good to know.

I just purchased - waiting for backorder - the XT and still have my safe sync from my 300D...since the XT doesn't have a PC socket I'll keep it.

[David_Hardy]

[ QUOTE ]
Thanks Doug! That's good to know.

I just purchased - waiting for backorder - the XT and still have my safe sync from my 300D...since the XT doesn't have a PC socket I'll keep it.

[/ QUOTE ]


Do make sure to check the SafeSync on your new cam before a job. Mine won't work on either my 1D2 or my 20D, works fine on a 10D/Pro1 though. Something to do with voltage I expect.

I had to buy a hotshoe flash adapter as I'm using my old Metz hammer flash and the pc socket is in just the wrong place!

David

[Doug_Kerr]

Hi, David,

[ QUOTE ]
Mine won't work on either my 1D2 or my 20D, works fine on a 10D/Pro1 though. Something to do with voltage I expect.

[/ QUOTE ]

It may be that the input of the SafeSync coupler will not tolerate what may be a modest closed-circuit voltage drop of the "electronic" X-sync outputs of the newer EOS cameras (I haven't yet tested to see what that might be).

I ran into a similar thing trying to fire a little (and cheap!) Vivitar 2800 flash from the PC terminal of my Kodak DC4800 compact digital camera (an electronic X-sync "contact"). The 2800 in fact had a relatively high-voltage sync circuit (about 140 V - perfectly OK per Kodak), but would not tolerate the modest "equivalent internal resistance" of the DC4800 X-sync circuit. (The 2800 would not fire reliably with 100 ohms in series with its sync circuit, and the DC4800 X-sync "contact" apparently exhibited the equivalent of about that.)

I ended up supplanting the Vivitar 2800 with a Vivitar 285HV, which worked fine. (The suggsestion of a Kodak bench tech consulted by a Kodak tech support rep; he had a DC 4800 himself and used a Vivitar 283 on it!)

Best regards,

Doug

[alex87]

Originally Posted by Doug_Kerr

Chuck Westfall, Director/Media & Customer Relationship, Canon USA, advises as follows regarding the flash sync circuit of the EOS Digital Rebel XT (EOS 350D):

*****
The EOS Digital Rebel XT uses a modified version of the EOS 20D's shutter unit. Consequently, acceptable trigger circuit voltage for both cameras is the same, i.e., 250 volts. Except for the original Digital Rebel, all current EOS digital SLRs (i.e., EOS-1Ds Mark II, EOS-1D Mark II, EOS 20D and EOS Digital Rebel XT) generate their X-sync signals electronically rather than mechanically. This is why they have higher acceptable trigger circuit voltage ratings than earlier models like the D30, D60, 10D and original Digital Rebel. These older models cannot be modified to achieve a higher trigger circuit voltage rating, since such a modification would require a different shutter mechanism as well as a complete redesign of the supporting circuitry.
*****

Best regards,

Doug

What about trigger voltage of Eos Digital Rebel XS (eos 1000d)? I have tried with an old nissin flash with about 60 Volts of trigger voltage and no error has occured. But i'm worried to have done a mistake because all says that the limits is 6V.

Thank you so much

Alex

[DougAxford]

I was just about to post then saw this new one that is close to what I'm needing.

Doug or Chuck,

Have the trigger voltages on the newer 50D, 40D and 5DM2 changed from the last report. I've also got a few older flash units that I'd like to use but most people seem to advise that they will ruin the camera.

I'm looking for a flash that is cheap and can be used on manual at variable power for flash fill on our sports T&I coming up in a few weeks. Even the 285 at 1/16 power is 3 times too much and I have to tape over the flash to cut it down. Since these units go through a lot of rough handling, it's crazy to use an expensive 580exII just to get a tiny pop of flash. BTW, the on-camera pop-up flash is WAAAY too strong for what I need, just in case you were going to suggest that.

I've been searching for alternatives but it seems everything now is eTTL and very few have variable manual settings, especially in the low price range. The only stuff I can find is used, hence the first question.

Thanks, Doug

[Doug_Kerr]

Hi, Doug,

Originally Posted by DougAxford

Have the trigger voltages on the newer 50D, 40D and 5DM2 changed from the last report.

I suspect all subsequent Canon EOS cameras basically follow about the situation Chuck described some years so (see above).

The bottom line is, "Almost anything will work, and what won't will not harm the camera".

I've also got a few older flash units that I'd like to use but most people seem to advise that they will ruin the camera.

I suspect that "most people" have no idea what the situation actually is.

I'm looking for a flash that is cheap and can be used on manual at variable power for flash fill on our sports T&I coming up in a few weeks. Even the 285 at 1/16 power is 3 times too much and I have to tape over the flash to cut it down. Since these units go through a lot of rough handling, it's crazy to use an expensive 580exII just to get a tiny pop of flash.[/quote]
Well, I use the Canon 580EX II for that (and everything else).

If you're concerned about the cost, you might be able to find a used 550EX.

Best regards,

Doug