Optical slave + pop-up flash?

It's quite hard to reliably find out what is the maximal flash hotshoe voltage of the 1000d. If you mount a flash that has too high trigger voltage it could fry your camera (or so they say). To be on the safe side I would feel comfortable only mounting low-voltage (about 6V) flashes on my camera. So, try to find out what is the trigger voltage of your Vivatar.

yes you can use the built-in flash to trigger your 285.
a standard optical trigger requires the use of the FEL technique, which also accounts for the exposure of the second flash at the same time.
FEL is similar to a flash reading lightmeter; except it sets the camera directly rather than the meter telling you what the settings should be.

There are also "digital" optical flash triggers that will accout for the "pre-flash" but here I think you would want to use manual exposure control.
set the power of the 285 for the distance from the flash to the subject.
then you might need to control the output of the pop-up flash with flash exposure compensation (FEC) I haven't tried that.
I know the FEL technique works.

How exactly do you use the FEL technique? What does FEL stand for?

Also, if the 285HV is safe for my 1000D, would it provide good results on the hotshoe?

i dont no about your xs but on my 40D i can turn the pre flash off, so it just fires one flash and i use it with my vivitar 285s and optical slaves all the time.

Ok...I think the way I'll go is to either just mount the 285HV to my hotshoe or trigger it with an optical slive by my pop up flash...

The FEL ( Flash Exposure Lock ) technique goes like this:
you set up your flash with the optical trigger oriented so it can "see" the camera's flash.

pop up the flash, set the camera to manual eposure mode with the ISO 100, shutter speed 1/125 and an f stop acoording to the distance from the flash to subject. ( You read this "guide number" {GN}off the chart on the flash. )
set the flash exposure by triggering the FEL (*) star button. ( be sure the round circle in the view finder has the main subject covered )
Now you have 16 seconds to recompse and focus the image.
Take the picture; if it seems too light reduce the F stop, too dark increase the f stop. if you have too much flash from the pop-up; use the Flash Exposure Compensation ( FEC ) to reduce the power from the pop-up.

Thanks a bunch? How do you use/set FEC?

on top of the camera where the buttons for ISO, Color and such are; there is one that has a lightning bolt under it, on the 20 D it is also the metering mode selector...
See your manual for more precise details.

Subfightersandman wrote in post #8393834
i dont no about your xs but on my 40D i can turn the pre flash off, so it just fires one flash and i use it with my vivitar 285s and optical slaves all the time.

How do you disable the pre-flash on the 40D? I search through the entire manual and menu system on my 40D and there is no specific item to do this.

drh - thanks!

liupublic - I think you can do this by turning off E-TTL.

Just figure out the onboard flash e-TTL mystery on the 40D. It can not be turned off for the Canon EOS DSLR system; however, it can be turned on a G series camera like Canon G9 or G10 by shifting into manual mode. That's where the confusion came from.

Additionally there is another catch:

So how will it work? I have a Canon 40D + Nissin Di-622 external flash. Nissin Di-622 in slave mode will ignore E-TTL's pre-flash and only fires when the main flash is firing. I just tried it at home and it works nicely. But there is a catch. With 40D, if C.Fb III -5 AF assist beam is On (0 default state). A pre-flash will fire in extreme low light situation to help focusing if on-board flash is popped up. I just noticed this when I point the camera to a very dark location to AF.

Sequence of events when NIssin Di-622 flash is in optical slave mode and using onboard flash:
1) AF by 1/2 down on shutter
2) flash to assist AF (Nissin Di-622 will not fire on first flash)
3) AF by 1/2 down on shutter
4) flash to assist AF (Nissin Di-622 fires because it thinks the main flash is firing)
5) Press down shutter to shoot
6) PreFlash for E-TTL
7) Onobard flash firing (NIssin Di-622 can not fire in time because it's not recharged yet)

To fix this problem:
1) disable AF assist beam
2) AF
3) Press down shutter to shoot
4) Pre-flash for E-TTL (ignore by Nissin)
5) Onboard flash firing (Nissin Di-622 fires at the same time)

It works pretty well so far.

In conclusion:
To make onboard pop-up flash work w/ optical trigger automatically, need the following:
1) Disable AF assist beam
2) Use an optical slave external flash that can ignore ETTL pre-flash
3) Adjust FEC accordingly if over exposed. I think ETTL-II metering will be off somewhat because the external slave flash did not emit anything during pre-flash. This needs a little bit of experiment.

I am not sure what other external flash can ignore E-TTL pre-flash. It appears to be a very new feature.

Thanks, liu. The YN460 can do this.

liupublic wrote in post #8408406
I am not sure what other external flash can ignore E-TTL pre-flash. It appears to be a very new feature.

E-TTL itself has existed at least since 1998, when the EOS 3 was introduced.
If you instead refer to slave triggers that can ignore the pre-flash, then I don't know for how long they've existed. I use Canon's wireless flash system, so I don't have to worry about that.

apersson850 wrote in post #8409345
E-TTL itself has existed at least since 1998, when the EOS 3 was introduced.
If you instead refer to slave triggers that can ignore the pre-flash, then I don't know for how long they've existed. I use Canon's wireless flash system, so I don't have to worry about that.

I have read that Canon wireless flash system does not work very well when overall light level is high. Also is there a line of sight issue? I read that Canon flash's sensor needs to be facing the camera and not obstructed.

For indoor, I did try try using optical slave setup when Nissin's flash sensor is facing away from the onboard flash indoor. and it does work fine. So it's definitely no line of sight requirement indoor within the same room.

All optical slaves suffer from being used in sunlight.
If your Nissin works, then so does the Canon. More or less, at least. The data transfer embedded into the pre-flashes in Canon's wireless multiple flash system may be more vulnerable to being overpowered by the sun, but apart from that it's the same thing.

I can put a Canon slave under the sofa and still get it to trigger when indoors in a normal living room. Outdoors it may work if you can shade the slave's sensor, or if it's cloudy, or...