AG-Schnozz wrote:
>>
My Vivitar is the equivelent of a T32 with zoom head. In my case it's a
full-stop faster.
<<
At wider angles this is often not the case. Most of the third party flashes
cover at best 28mm and often only 35mm.
The T32 covers a 24mm lens. So **at the equivalent coverage*** of the T32 the
T32 often has the edge in GN or is at least competitive. I have to agree the
T32's zoom is mediocre so it does not do so well when zoomed. It wastes a lot
more light than it should. If you don't often use the WA coverage of the T32
the 3rd party zoom flashes are often more conveniient and competitive.
To illustrate this all : the popular Vivitar 3700, 4600 and similar 5600
standard heads only cover 35mm lenses which inflates the GN relative to the
T32's wider coverage spec.
An interesting comparison is say the T32 and the 4600. With standard head,
the 4600 is rated GN 100 @100ISO.
The T32 is about the same GN but the T32 covers a 24mm lens while the Vivitar
covers only 35mm. In fact the 4600 with the 28mm fresnel lens has a GN of 70
and with the ultra wide 21mm adapter it is rated GN 50, thus the T32 is
really significantly brighter . These are laws of dimminishing returns: To
double the GN you need roughly 4X the energy assuming lamp/reflector
efficiency constant. This implies the energy stored in the std head of the
4600 is most likely less than half that of the T32.
The large Metz on camera flashes are more flexible than the T32 with
comprable or better performance at WA and a better zoom.
Here is an old post I made previously on this topic a long time ago:
>>>
at 100ASA: GN
T32 GN in ft 104 (24mm coverage) <==
4600 standard head 100 (35mm coverage)
4600 with WA adapter 70 (28mm coverage)(calculated
value 70)
4600 calculated for 24mm 56 (theoretical,no adapter available
for 24mm) <==
4600 with extra wide adapt 50 (21mmcoverage) (theoretical
value 47)
T32 with 21mm adapter 72 (21mm coverage) (theoretical
value 83)
The T32 has a smaller volume than the 4600 but has almost twice the effective
GN. Since the GN increases as approximately the square root of energy stored
(Joules or W-s) all things being equal , the T32 is really much more powerful
than the 4600 although superficially they have same GN
Interestingly Olympus's zoom head adapter for the T32 appears to be very
inefficient as the GN does not increase nearly as much as one would expect.
(numbers not shown) The manufacturer's GN's for the 4600 with adapters look
rather optimistic given the adapters probably loose some additional light.
The 21mm WA adapter for the T32 has significant loss over theoretical,
(possibly because it is a diffuser not a lens?) but even so it is still more
powerful than the 4600.
<<<
Regards,
Tim Hughes
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