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I tried several flashes on my Canon EOS Rebel SL3, but it didn't work. I'm wondering which pin on hot shoe triggers the flash?

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5 Answers 5

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The T7/2000D, T100/4000D, and SL3/250D are all missing the big central sync connector on the hotshoe, which is the ISO standard signal for sync. This basically broke compatibility with any single-pin manual speedlight (e.g., YN-560 IV, or Godox TT600) which can only communicate that one signal.

And while firmware updates fixed compatibility issues with Godox's 2.4 GHz eTTL-capable speedlights for the T7 and T100, apparently those same updates do not work for the SL3. Only the Godox transmitters have received SL3-specific compatibility firmware updates.

If you need an affordable on-camera flash unit for the SL3, a Canon EL-100 is probably your best option.

But if you really need to use a 3rd-party single-pin flash, a Godox X1T-C or X2T-C transmitter can be used kind of like a hotshoe adapter to give you back the sync connection if you sandwich it between the hotshoe and the flash.

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  • \$\begingroup\$ This does not answer the question: “which pin on hot shoe triggers the flash?” \$\endgroup\$ Aug 29, 2023 at 1:27
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    \$\begingroup\$ @MikeSowsun; I think I did. For me, the problem with the question is that a pin is what's on the flash foot vs. the contacts on the hotshoe. Pins are what are pushed against a contact. \$\endgroup\$
    – inkista
    Aug 30, 2023 at 0:39
  • \$\begingroup\$ Okay, on the SL3, which contact triggers the flash? \$\endgroup\$ Aug 30, 2023 at 13:54
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    \$\begingroup\$ @MikeSowsun, ah. Gotcha. Yes, I did not answer the question. I answered what I thought was the question of what flash will work on an SL3. Not gonna delete, though, as might still be useful. \$\endgroup\$
    – inkista
    Aug 30, 2023 at 18:55
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It is a combination of pins 2 and 3; when data (pin 3) is at logic high, and clock is held at logic low for 4ms (pin 2), then the flash fires.

enter image description here

Here's a DIY to add a microcontroller to an ISO standard speedlight in order to monitor pins 2-3 and trigger the flash appropriately. https://www.instructables.com/Generic-Speedlite-Hack-for-Canon-EOS-1500D/

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    \$\begingroup\$ This answer is only correct for a “hacked” flash. Pins 2 and 3 alone will not cause a flash to fire on an unmodified flash with a camera that does not have a Center sync contact. \$\endgroup\$ Aug 30, 2023 at 20:41
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As you can see in the top view:

enter image description here

The hotshoe of the SL3 is missing the big central contact which has been the standard trigger pin for decades, so it will only work with flashes designed for the Canon contacts (Canon, but possibly some YongNuo)

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  • \$\begingroup\$ I know that, I mean between metal base & which one of 4 pins? \$\endgroup\$
    – Kamran
    Aug 29, 2023 at 0:31
  • \$\begingroup\$ My money on the ETTL pin in this diagram, but it's probably a command signal, not just a contact. \$\endgroup\$
    – xenoid
    Aug 29, 2023 at 0:38
  • \$\begingroup\$ This does not answer the question: “which pin on hot shoe triggers the flash?” \$\endgroup\$ Aug 29, 2023 at 1:26
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Using my 80D and a 430EX II, I went through a process of elimination by covering the various hotshoe contacts with black electrical tape.

I was able to determine that contacts(pins) 2,3, and 4 are ALL needed in order for an ETTL flash to be triggered by a camera without the normal contact in the center.

Contact(pin) 5 is the only one that was not needed for the flash to fire. I am not sure what “AF Assist” means, but I believe it may communicate subject focus distance to the flash in order to fine tune the ETTL II flash exposure. Not all Canon lenses have this capability and it is not needed for ETTL to function.

Other than the Center contact, no other one contact by itself would trigger the flash to fire.

enter image description here

enter image description hereenter image description here

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None of the contacts on the SL3 hot shoe trigger the flash in the way you seem to expect. That is, the large central contact that does what you describe is missing from the SL3 hot shoe.

enter image description here

None of the contacts included on the SL3 hot shoe complete a simple circuit that causes the flash to fire. The contacts on the SL3 hot shoe only work by communicating data to the TTL micro-processor in a compatible flash or flash trigger. The attached flash or flash trigger then uses the data sent to it via pins 2, 3, and 4 and applies its own logic circuits to decide when and at what power to "fire" the flash.

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