Thanks everybody for answering the original question. It seems that the
Olympus flash system is quite basic.
Chuck's numerical analysis is very interesting. When I got some time, I will
measure the light output with some high speed light sensors.
EDB
-----Original Message-----
From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
Sent: July 13, 2012 12:08 PM
To: Olympus Camera Discussion
Subject: [OM] T32 power and recharge test, was: T32 in auto +OM4T in manual,
what's going to happen?
I'm well aware of the premature lighting of the ready light. It turns on at
perhaps 90% of available power. In all of my testing I've waited at least
twice the time required to get the ready light on. If the ready light turns
on in 10 seconds I've waited at least 20 seconds to fire the flash. I've
also used fresh AA alkalines in my testing since the power output from the
higher voltage (1.5 volt) batteries is 0.5 stop higher than that from NiMH
(1.2 volt) batteries. But one must be willing to change batteries
frequently if using alkaline for testing since after 20-30 full power dumps
from a T-32 the alkaline batteries have already dropped from 1.5 volts to
1.2 volts. I've also tested T32s with my high voltage battery pack. My
recollection is that it increases power over alkalines but I don't have any
notes on the result.
Here are some notes I made in testing four different T32s. Note that tests
were conducted in my living room (15x23 feet) which has very pale blue walls
(nearly white) and a white 8' ceiling. Lots of reflecting surfaces. As
you'll see below even 20 seconds doesn't get a T32 to full power. Power
output measured with my Sekonic L-358
---------------------------------------------------------------------
T-32 flash power and recharge test
@ 10 feet, ISO 100, no diffuser, max power
Center Edge of 28mm field of view
1 unit = f/ 8.0.2 f/ 5.6.8
2 units = f/11.0.1 f/ 8.0.6
4 units = f/ 16.0.1 f/ 11.0.7
@ 10 feet, ISO 100, small umbrella, max power
Center Edge
1 unit = f/ 4.0.0 f/ 2.8.6
2 units = f/ 4.0.9 f/ 4.0.5
4 units = f/ 8.0.1 f/ 5.6.7
@ 10 feet, ISO 100, no diffuser, at 1/4 power
Center Edge
4 units = f/ 4.0.2 f/ 2.8.7
Note: All 4 units test within 1/3 stop of each other. Output is very
sensitive to battery voltage. AA alkalines produce about 1/3 stop less
output after 20-30 flashes.
Output with alkaline AA's at 1.54 volts = f/ 8.0.4, at 1.33 volts = 5.6.9.
Actual measured guide number with fresh alkalines is only 84 vs.
spec of 104.
5.6.9 is the max observed power output using 1800mah NiMH batteries or
0.5 stops below max with alkaline.
A single T-32 is approx. 100 watt seconds compared to Lumedyne at 100 w/s
Recycle times with 1800mah NiMH batteries. Power measured at 10 ft.:
Time Power, f/stop
5 sec f/ 4.0.9
7.5 sec f/ 5.6.3
10 sec f/ 5.6.6
15 sec f/ 5.6.7
20 sec f/ 5.6.8
Note: Max of f/5.6.9 observed for NiMH batteries still not achieved in
20 seconds.
Chuck Norcutt
On 7/13/2012 9:52 AM, Ken Norton wrote:
>> It gives you *it's* full power. It just doesn't happen to be equal
>> to the spec. I've tested many flashes and... none of them do.
>
> It does EVENTUALLY get there, but long after the flash ready light comes
on.
>
> I recall that Olympus did game the flash power ratings a little bit.
> They weren't alone in this as most companies did to one extent or
> another. I became keenly aware of this when I bought the IS-1 and G40
> flash. The IS series uses the distance measurement from the auto-focus
> system to determine power output. As long as the subject was in focus,
> the subject would be properly lit.
>
> More or less...
>
> What Olympus did was under power the flash slightly to accomodate
> reflected light. So, the GN rating wasn't based on direct flash
> without reflections, but on direct with some reflection. Probably
> about 1/3 stop worth.
>
> However, I'm not entirely sure this is uniform across all platforms.
> The T45 is pretty much dead on. I've carefully measured it in
> non-reflective environments with a couple different flash meters and
> each manual setting is consistantly within 2/10 of a stop.
>
> AG
>
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