E-TTL vs E-TTL Optical Wireless (multiple flashes) vs E-TTL with radio triggers yn-622c

Started 7 months ago | Discussions thread
Kasra A
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Re: E-TTL vs E-TTL Optical Wireless (multiple flashes) vs E-TTL with radio triggers yn-622c
In reply to ScratchDisk, 7 months ago

ScratchDisk wrote:

Hi, I would agree with most of the above . . .

I would only add, (based partly on use & partly on reading Canon patents), that under ETTL II:

1) The system does not know off-cam flash to subject distance.

2) It does indeed measure pre-flash returns sequentially by group. Under the Light/IR type at least, it assumes that A group plus B group flash illumination summed together will adequately illuminate 'the subject'. Under the Light/IR incarnation, C group illumination is intended for the background (or at least, a surface exclusively illuminated by C group Speedlite(s)).

3) A single power fraction setting instruction is sent per Group.

HTH, Donald

Thanks Donald.

Good to know that! Sequential reading makes a lot of sense.
So basically, if we ever needed to to add a background light, it's better to be put on group c.

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