430 EX-II slave automatic zoom level?

[Bugman]

when the 430 EX-II is off-cam is put into slave mode, it defaults to manual 24 mm zoom level.

I can then adjust the zoom until the "M" is gone - theoretically in an automatic zoom setting now?

Does this mean that when I do a TTL exposure with the 430 EX-II off cam it will automatically adjust the zoom level for my lens?

Or is this automatic zoom level adjustment by wireless optical just impossible?

Does automatic zoom level adjustment only occur if the flash is ON-cam?

[RobertTheFat]

When the flash is on-camera, the camera can tell it the zoom setting of the lens. But when it's off-camera, how would it know what zoom setting to use to cover the subject? Or even whether it's actually looking at the subject? So you could set the flash's zoom to whatever you wanted, but I don't see how the flash would ever have enough information to know to change it.

[Bugman]

ok - so when I have it off-camera, do I just set it to "M 24mm"  or to "24mm" without the M in front of it? 

Or I think it probably doesn't matter -

I think you're saying that as it is off-camera it just fires off at "24mm" zoom level, in order to cover as wide an area as possible, unless I manually set it to a higher zoom level.

Is this correct ?

thanks so much for your help!

[RobertTheFat]

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@Bugman wrote:

ok - so when I have it off-camera, do I just set it to "M 24mm"  or to "24mm" without the M in front of it? 

Or I think it probably doesn't matter -

I think you're saying that as it is off-camera it just fires off at "24mm" zoom level, in order to cover as wide an area as possible, unless I manually set it to a higher zoom level.

Is this correct ?

thanks so much for your help!

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That would be my take on it. But I almost never use off-camera flash, so I could easily be missing something. It's likely that one of the other regulars will have a more definitive answer.

[TCampbell]

When it's off camera you can manually set it to any zoom level you want.  You can also manually control the zoom even when on camera except that normally the camera communicates with the lens and tells it what zoom level to use.

Syl Arena's book "The Speedliter's Handbook" is a great resource on understanding the Canon E-TTL system.

[Bugman]

I was thinking that if ETTL settings were communicated to the off-cam flash, then the zoom length might also be communicated.  When the flash is on-cam, it changes it's zoom level when I adjust the lens zoom level, and when you use ETTL radio triggers, the off-cam flash will change zoom as you zoom in and out with your lens,

but apparently that is not so when using the Canon optical slave system.

thank you for your help! I'll take a look at the Syl Arena book

[TCampbell]

The Canon algorithm only uses the lens focal length if the flash is on the camera AND pointed straight ahead. If you swivel or tilt the flash then it wouldn't be valid (and the flash knows this).

If located off camera the there's no way for the camera to know that the flash is at the same distance as the camera so it has to ignore that info.