I was rereading your response and didn't understand your last result.
If a bounce exposure works at f/2.8 and ISO 100 it ought also to work at
f/5.6 and ISO 400 as these are equivalent exposures.
The only reason I can think of why it would not is that the f/2.8 & ISO
100 mighe be on the ragged edge of working and there is enough
variability in the accuracy of the the electronics that the f/5.6 ISO
400 setting isn't really exactly equivalent. If the ISO slider will go
to 800 try it at f/5.6 and ISO 800. That should be more than enough to
overcome any slop in the controls or power output. If it still doesn't
work I can only guess at something wrong with the flash but I don't know
what.
I recently sold a Sunpak 522 to Phil and calibrated it for him before I
sent it. The 522 has a 7 stop manual power control range with output
selectable in 1/3 stop increments. As expected, the top end of the
manual power control was about a stop less power output than the spec
would indicate. Possibly age but more likely just as it was made.
Then, the next stop or so down was quite compressed and from then on the
indicated power markings fairly well indicated an actual drop of one
stop if the power was turned down one stop. But any individual setting
could easily be 1/3 stop off. There are at least one or two stops on
the dial where the output doesn't seem to change from one click to the
next... at least at the 1/3 stop degree of accuracy. If I set the meter
for 1/10 stop accuracy you can see some change between settings A and B
but the difference isn't measurable when rounding of to the nearest 1/3
stop.
If your 266d isn't any more accurate than this 522 it may well be that
*indicated* equivalent exposures are *not quite* equivalent.
Chuck Norcutt
Chuck Norcutt wrote:
>
>>
>> One other thing I noticed about the auto settings is that when bouncing, the
>> auto setting with the larger of the two apertures must be used to get an OK
>> signal from the flash. The smaller apertured auto setting and the large one
>> both give the OK lamp for head on flash, but only the larger aperture will
>> give the go-ahead when bounced. This seems to be the case no matter what
>> film speed the flash is set to. So, my rule of thumb for bouncing TTL will
>> probably be to use apertures within 1 stop of that larger auto aperture.
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