>Hi > >Do you know any reason why it would be dangerous >to connect the flash PC socket (or hotshoe middle >contact with an adaptor) in EOS cameras to the >remote release connector full-press pin (and >ground pin)? I will never do that, but it can work. >The purpose is to trigger the second camera by the >flash-on information from the first camera. This way >I could use one flash with two bodies and thus get >two shots at once. I don't think it's the best way to do that. You can also build a "Y" cable for the remote socket and fire both cameras at the same time. You can use a pair of diodes to obtain some isolation. You only need to be sure that both shutters are open when the flash is triggered. You can do that conecting the flash to the larger lag-time body or selecting a smaller shutter time for the flash camera and using second curtain sync. >Naturally the first camera needs to be in manual or >at least Tv mode with long enough shutter speed. At first curtain the flash is triggered as soon as the curtain is full open, so the important point is to be sure that the non flash body has the first curtain full open when the flash body triggers its flash. I you use, for instance, an EOS 3 and an EOS 50, just put the flash on the EOS 50, as the EOS 3 features a smaller lag an you will sure that it's first curtain will be full open when the EOS 50 flash is triggered. >My understanding is that the PC socket (or actually >the semiconductor switch inside the camera body) >works like a relay and should tolerate the 5V and <1mA >voltage/current coming from the remote release socket. Yes, but it's not always a true relay. It can be a SCR, in this case, it only works if there is enough current. >I have already shortly tested this in "lab conditions" >without film and found out that it works only if I keep >the second camera shutter release in half-pressed position. >I used one EOS-3 and one 50E. > >The 50E shutter never fires unless the shutter release is >half-pressed. That's the way it works. >When I trigger EOS-3 manually by shortcircuiting the ground >and "full-press" pins in the remote socket it works >but when I connect EOS 50E PC socket to EOS-3 remote release >socket it doesn't work unless I keep the EOS-3 shutter >manually half-pressed. It might be due to the (too) short >flash trigger pulse from EOS 50E. I think it was around >60ms while in EOS-3 it seems to be about twice as long. >Unfortunately I don't have two EOS-3s to check. >Perhaps keeping the shutter release half pressed decreases >the EOS-3 shutter lag? Don't know. >Any comments? I won't do that. I will use a remote release with two cables for the two bodies. I will set, for instance, 1/60 and second curtain on the flash body and 1/30 in the non flash body. Or, if two different bodies are used, I will put the flash in the longer lag body. I assume that the flash is the main source of light. If it's not true it will be more difficult, but it can also be done. >Vesa Best regards Vicente * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
