If the available energy to each head is cut in half (1 stop) then the
guide number would nominally be reduced by the square root of 2.
Dividing 28 by 1.4 I get 20 instead of 22. But I guess that's close enough.
Chuck Norcutt
Jeff Keller wrote:
> The guide number is limited by the energy stored in the capacitors
> and the width of field illuminated. If two heads are sharing the same
> energy it seems reasonable that the guide no. would go down ...
> -jeff
>
> On 7/19/07, usher99@xxxxxxx <usher99@xxxxxxx> wrote:
>> Piers, Thanks again for these.?
>>
>> Weird that on the Alan Wood site in one place near where he
>> mentions the calculator panels (T28), the? GN with one flash is
>> listed as 22 and 28 with 2 heads.? It is the opposite later on his
>> site and anywhere else, including on your panel pdf.?? Must be a
>> mistake on the AW site.? I don't know how the GN would go down with
>> 2 heads (must be the case), unless the controller T power control
>> attenuates the power to both.? Perhaps there is something weird
>> about GN's at macro distances.? Manual macro flash shouldn't be as
>> weird as quantum effects, though Heisenberg seems to lurk over my
>> shoulder when I try it.
>>
>> http://www.alanwood.net/photography/olympus/t28-macro-twin-flash.html
>>
>>
>> Mike
>
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