USHER99@xxxxxxx wrote:
> I trust one can use Chuck's nice summary of John Shaw's approach to
> calculate off camera non-TTL fill flash for Macro??
I don't see any reason why the flash meter measurement should be any
different than ambient light measurement.
Another member
> kindly provided the formula for the light attenuation due to
> magnification (10/31), though it is not clear to me that that
> accounts for the extension per se as well. Would the thyristor in
> the hot shoe read approximately as the incident light meter?
The thyristor in the flash is reading reflected rather than incident
light. That said, it might work OK except for three sticking points.
1) the flash sensor may not have a good view of the action on a closeup
2) the sensor may not be fast enough to respond to such close action
3) the same adjustments for macro light loss would have to be applied to
the flash by lying about aperture or ISO setting.
Chuck Norcutt
I
> suppose one would need to repeat the process with a 2x teleconverter
> and/or a combination of ext tubes and TC. I suppose this is not too
> much trouble after the charts are constructed. Mike
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