Does canon 70D has a bulit in flash trigger ! Or I need a third party device !

[thirdeye]

Hello. Well I have off camera speedligt but I couldnt get it fier without having the built in flash on . what if I wanna use the off camera speed light without the one on the camera . as I know that canon has a regier bilut in and I don't need a third party device !
Thank u

[TCampbell · Accepted solution]

The flash trigger uses the on-camera flash and it is optical. You can "disable" the flash to use only the off-camera flash, but the on-camera flash still needs to be raised.

It will fire a pre-flash while the camera shutter is still closed to evaluate light (if using E-TTL instead of manual) and also to send instructions to the off camera flash (again, for E-TTL... but also to tell the off-camera flash when to fire.). The timing has a fractional delay. So it tells the off-camera flash to fire, the shutter opens, then the off-camera flash (and only the off-camera flash) firs, then the shutter closes.

This all happens VERY quickly and you'd swear both flashes fired at the same time -- when actually the on-camera flash fired only when the shutter was closed, and the off-camera flash fired its last shot when the shutter was open.

To do this, you'll need to go into your flash control menu and tell it you want to "disable" the on-camera flash. Disabling doesn't mean the flash doesn't get used... It just means that it doesn't fire at that final moment when the shutter is actually open.

Also note that because it uses visible light (not IR) to transmit instructions, the off-camera flash's sensor must have line-of-sight to the on-camera flash. If this is a flash like the Canon 430EX II speedlite, the sensor is in the lower part of the flash. That means you may need to rotate the lower half of the flash to face the camera, then swivel the flash head to send light wherever you need it. If the lower unit simply faces forward you will find it to be less reliable (especially over larger distances or outdoors.)

[thirdeye · Accepted solution]

Thank you so much ,that was very helpful.
I'll need to try it again .

[TCampbell · Accepted solution]

The flash trigger uses the on-camera flash and it is optical. You can "disable" the flash to use only the off-camera flash, but the on-camera flash still needs to be raised.

It will fire a pre-flash while the camera shutter is still closed to evaluate light (if using E-TTL instead of manual) and also to send instructions to the off camera flash (again, for E-TTL... but also to tell the off-camera flash when to fire.). The timing has a fractional delay. So it tells the off-camera flash to fire, the shutter opens, then the off-camera flash (and only the off-camera flash) firs, then the shutter closes.

This all happens VERY quickly and you'd swear both flashes fired at the same time -- when actually the on-camera flash fired only when the shutter was closed, and the off-camera flash fired its last shot when the shutter was open.

To do this, you'll need to go into your flash control menu and tell it you want to "disable" the on-camera flash. Disabling doesn't mean the flash doesn't get used... It just means that it doesn't fire at that final moment when the shutter is actually open.

Also note that because it uses visible light (not IR) to transmit instructions, the off-camera flash's sensor must have line-of-sight to the on-camera flash. If this is a flash like the Canon 430EX II speedlite, the sensor is in the lower part of the flash. That means you may need to rotate the lower half of the flash to face the camera, then swivel the flash head to send light wherever you need it. If the lower unit simply faces forward you will find it to be less reliable (especially over larger distances or outdoors.)

[RobertTheFat · Accepted solution]

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@TCampbell wrote:

Also note that because it uses visible light (not IR) to transmit instructions, the off-camera flash's sensor must have line-of-sight to the on-camera flash. ...

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I think that statement is a bit misleading and probably not what you meant to say. Like the optical pre-flash, the IR transmitter is uni-directional, so the IR receiver on the off-camera flash needs line-of-sight access to the on-camera flash. While there's a bit more wiggle room with IR because IR waves are longer than those of visible light, that effect should not be relied on. It's only radio transmitters that are genuinely omni-directional and don't require the off-camera flash to have line-of-sight access.

[TCampbell]

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@RobertTheFat wrote:

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@TCampbell wrote:

Also note that because it uses visible light (not IR) to transmit instructions, the off-camera flash's sensor must have line-of-sight to the on-camera flash. ...

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I think that statement is a bit misleading and probably not what you meant to say. Like the optical pre-flash, the IR transmitter is uni-directional, so the IR receiver on the off-camera flash needs line-of-sight access to the on-camera flash. While there's a bit more wiggle room with IR because IR waves are longer than those of visible light, that effect should not be relied on. It's only radio transmitters that are genuinely omni-directional and don't require the off-camera flash to have line-of-sight access.

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Depends on the unit.   Here's a great video by Syl Arena (sponsored by Canon):

https://www.youtube.com/watch?v=5gmgN8l7UFg

The video is nearly 2 hours long (but it's a GREAT video and I do recommend it).  But if you fast-forward to the 1 hr 39 min point and start playing from there, he starts talking about the E-TTL communication.

On cameras like the T5i, it's optical / visible light using the flash tube itself to send instructions.  But controllers like the ST-E2 actually do transmit IR (not visible light).   (Note that the ST-E2 does have a focus-beam emitter which does emit a red focus-pattern and that is visible red light.)  The receiver can see either visible or IR -- that part doesn't matter.  IR is better at bouncing off objects and getting a signal through anyway -- but that's mostly an indoor thing.  When you're outside, there's probably not so much to bounce the signal off -- if the sensor cannot "see" the emitter with direct line-of-sight, then the slave may fail to fire.

[thirdeye · Accepted solution]

Thank you so much ,that was very helpful.
I'll need to try it again .

[thirdeye]

what if i want the off camera speedlight to be the master not slave . what I understood is the built in flash will be the master and the off camera will be slave !

[TTMartin]

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@thirdeye wrote:
Hello. Well I have off camera speedligt but I couldnt get it fier without having the built in flash on . what if I wanna use the off camera speed light without the one on the camera . as I know that canon has a regier bilut in and I don't need a third party device !
Thank u

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The built in flash will fire while the shutter is open to thrigger the off camera flash. It will fire at it's lowest power level even when you have the on camera flash set to 'off''.

If you absolutely need no output from the on camera flash, you can put something in front of the flash that only allows the IR portion of the light from the flash through. I don't think Canon makes one, but, Nikon does SG-3IR Replacement IR Panel for the Built-in Flash.

[TCampbell]

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@TTMartin wrote:

The built in flash will fire while the shutter is open to thrigger the off camera flash. It will fire at it's lowest power level even when you have the on camera flash set to 'off''.

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It does not fire at all once the shutter is open.  The flash you see is just the "pre-flash" (shutter is still closed).

See page 206 of the manual.

In the menu, go to "Flash Control",

Set "Flash firing" to Enable (otherwise it'll only used as focus-assist.

Select "Built-in flash func. setting" (which opens a new menu)

Select "Wireless func." and pick the option which ONLY shows the profile of an external speedlight (and does not show the profile of the pop-up flash).  

In that mode the internal flash will only operate as a commander.  It'll use the flash tube only prior to opening the shutter.  When it ultimately gives the order to fire the external flash, the external flash receives the order but starts a very brief time-delay to allow the camera enough time to fully open the shutter.  The external flash then fires (by itself... no internal flash).  The shutter closes.

This all happens so fast you'd swear it was just one flash and that there was no delay between internal vs. external flash (but there is.)

BUT... if you set up the internal flash per the instructions, but do not setup an external flash, then take a test shot in a dark room, you will visibly (with your eyes) see the flash fire.  But when you inspect the image it capture, you'll see that it's black -- no flash at all.

BTW, to avoid confusion, there's also a menu option for "external flash" -- that's actually settings to control a shoe-mounted flash.  Canon uses the term "internal" for the pop-up flash, "external" for a shoe-mounted flash (a Canon Speedlite attached to the camera hot-shoe) and "wireless" to refer to a remote flash not mounted in the hot-shoe.

[TTMartin]

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@TCampbell wrote:

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@TTMartin wrote:

The built in flash will fire while the shutter is open to thrigger the off camera flash. It will fire at it's lowest power level even when you have the on camera flash set to 'off''.

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It does not fire at all once the shutter is open.  The flash you see is just the "pre-flash" (shutter is still closed).

See page 206 of the manual.

In the menu, go to "Flash Control",

Set "Flash firing" to Enable (otherwise it'll only used as focus-assist.

Select "Built-in flash func. setting" (which opens a new menu)

Select "Wireless func." and pick the option which ONLY shows the profile of an external speedlight (and does not show the profile of the pop-up flash).  

In that mode the internal flash will only operate as a commander.  It'll use the flash tube only prior to opening the shutter.  When it ultimately gives the order to fire the external flash, the external flash receives the order but starts a very brief time-delay to allow the camera enough time to fully open the shutter.  The external flash then fires (by itself... no internal flash).  The shutter closes.

This all happens so fast you'd swear it was just one flash and that there was no delay between internal vs. external flash (but there is.)

BUT... if you set up the internal flash per the instructions, but do not setup an external flash, then take a test shot in a dark room, you will visibly (with your eyes) see the flash fire.  But when you inspect the image it capture, you'll see that it's black -- no flash at all.

BTW, to avoid confusion, there's also a menu option for "external flash" -- that's actually settings to control a shoe-mounted flash.  Canon uses the term "internal" for the pop-up flash, "external" for a shoe-mounted flash (a Canon Speedlite attached to the camera hot-shoe) and "wireless" to refer to a remote flash not mounted in the hot-shoe.

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Try it yourself in a mirror.

Just be sure to use a high enough ISO and wide enough aperture to pick up the flash at minimum power.

I just tested iit with my 7D and 430EX II in slave mode, it fires at very low power when the shutter is open, and is visible in the photo.

And yes I had the menu settings correct.

 If you absolutely can't have the onboard flash visible at all in the photo, you need to use some sort of IR filter (IR transmitting, not IR cut) like I linked above.

[TCampbell]

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@TTMartin wrote:

Try it yourself in a mirror.

Just be sure to use a high enough ISO and wide enough aperture to pick up the flash at minimum power.

I just tested iit with my 7D and 430EX II in slave mode, it fires at very low power when the shutter is open, and is visible in the photo.

And yes I had the menu settings correct.

 If you absolutely can't have the onboard flash visible at all in the photo, you need to use some sort of IR filter (IR transmitting, not IR cut) like I linked above.

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Interesting... I'll have to test this.  I tested by shooting in a dark room and noted that while I could see the flash fire, the photo captured by the camera was black.   I may test the mirror when I get a chance (my 5D II & III don't have built-in flash, but I have a 60Da.  I don't have a 70D.)  

I'm wondering how bright the reflection in the mirror was.  Might it have been afterglow of the gas cooling down?