600EX-RT Owners – Flash Algorithms?

Started Jun 1, 2012 | Discussions thread
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ScratchDisk Veteran Member • Posts: 3,582
600EX-RT Owners – Flash Algorithms?

600EX-RT Owners – Flash Algorithms?

On all of the Canon sponsored info I’ve read about the new 600Exs, I’ve not seen answers to the following question.

Background: In the ETTL II and 5xxEx era Canon specified ‘Evaluative for Flash’ and ‘Average for Flash’ in the relevant instruction manuals (the setting being accessed from within either the cam’s CFns or from the cam’s flash menu screen, under Flash Mode or Flash Metering).

They added the fact that using FEL would over-ride whichever of the above was in use – and – impose a central (c3% - 1.5%) pre-flash meter and lock.

A fourth Flash Mode was left very much less well documented. This fourth flash mode also over-rules Eval or Av, but is only enabled when all of the following conditions strictly apply together.

1) The speedlite (single) is either attached via an OC-E3 cable (or close clone of same), or is in the camera’s hot-shoe directly. (So it can be ‘off-cam’, but it would have to be ‘wired’ – and not just a pc link etc.)

2) The speedlite configuration has to be in its straight-ahead or cobra orientation. i.e. with the flash head bent forwards to zero degrees – not in any sort of bounce configuration.

3) Canon Wireless must be disabled. There must be no ‘master’ nor ‘controller’ functionality at work.

4) The lens in use must be a ‘Distance Reporting’ type of Canon EF or EF-S lens.
All 4 conditions must be fully satisfied for this fourth flash mode to kick-in.

There is, AFAIK, no official name for this mode, but you might call it the ‘Achieved focus distance dominated’ flash mode. (This is not implying that the focus point in use moves, in any way, pre-flash metering emphasis within the frame.)

The point is that this fourth flash mode does not ‘allow for’ the effect on flash exposure of the use of modifiers or gels. Whereas, Eval, Av and FEL all do.

Question; Does the new 600EX-RT follow the fourth flash mode or not?

To test this, the 4 conditions above would have to be strictly met. Then simply add a light modifier – perhaps just a 2 stop layer of diffusion material – between speedlite and subject, while keeping all other parameters unchanged. You would need to be working comfortably within the power/range envelope of the speedlite when the modifier was in use. (The new Canon 600 gel system is a special case – please investigate that separately, Tx!)

Thank you very much for sharing your conclusions!

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