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Re: [OM] Flash question on RFF

Subject: Re: [OM] Flash question on RFF
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Thu, 20 Nov 2008 10:38:32 -0500
I suspect that he may not be fully sorted yet.  I don't belong to the 
Rangefinder forum so perhaps you or Piers might post some of this.

First, a warning based on the poster's intent to use the T32 at 20 
meters.  Using the T32's calculator panel (on the auto/manual side of 
the panel) you can see that, even at ISO 400, an f/2.8 lens will be 
required to reach 20 meters.  Actually, the calculator panel indicates 
something between f/4 and f/2.8 which my manual calculations show to be 
f/3.1.  However, since most flash manufacturers generally fib by at 
least 1/3 stop on their guide numbers (and the T32 is no exception) the 
actual requirement at 20 meters and ISO 400 will likely be f/2.8.  If 
you don't have an f/2.8 lens that will reach the distance required then 
a film faster than ISO 400 will be required or else accept a stop or 
more of underexposure.

Of course, this all assumes that the T32 is the only light source.  If 
shooting a stage production, for example, which provides moderately 
bright ambient light a slower film and lens may be OK.  It also assumes 
that you don't have the T32 "zoom adapter" which narrows the angle of 
view and raises the ISO 100 guide number to as high as 42 at the 135mm 
setting.  In any case, be aware that the T32 may be approaching its 
limits here.

Now to some questions that were posed but not answered.  Yes, the OM-2sp 
has a "flash ready" signal in the viewfinder.  It's at the extreme upper 
left of the viewfinder and is a green (or red) square with the symbol of 
a lighting bolt in the center.  The flash ready signal glows when the 
flash is charged and blinks very rapidly for a couple of seconds after a 
*correct* exposure had been made.  If it simply goes out then there has 
been an under or overexposure which is indicated by "under" and "over" 
(text) indicators between the top of the shutter speed scale and the 
flash ready signal.  These may be extremely difficult to see under dark 
conditions since they are not illuminated like the ready signal is.  The 
"over" indicator sits directly above the shutter speed scale and the 
"under" indicator is above that.  It may be possible to see them better 
if you use the viewfinder illuminator button (right side of camera below 
the prism) but it only stays on for 10 seconds and it's difficult to 
coordinate that with your shot.

If your OM-2sp has a green ready light in the viewfinder then it's the 
original design which draws its power from the camera batteries.  If the 
ready light is red then it's a later design which draws its power from 
the flash batteries.  Olympus modified many or the original green type 
to the red type because of complaints about excess battery drain to 
power the ready light.  Just be aware that, when the flash is powered on 
  the camera may be using more power than usual if you have the green 
ready light.  In any case, be sure to use fresh batteries and make sure 
you are using silver oxide rather than alkaline batteries.  Alkaline 
batteries will not last very long in OM cameras such as the 2sp which do 
not have on/off switches.

The reason you may not have seen the ready light come on is that you may 
have been doing test shots without film in the camera.  The OM-2sp's 
exposure system is TTL OTF (Off The Film) which means the metering 
system reads the light reflected from the film during actual exposure. 
If there is no film in the camera the only thing the meter sees is 
reflection from the black pressure plate.  Not much to reflect from and 
certainly not enough to indicate a correct exposure.  If you have a test 
roll put that in the camera before doing exposure tests.

With the camera in Program or auto mode and the T32 in use in TTL mode 
(calculator panel turned to the blank side) or in "normal auto" mode 
(calculator panel outward) the "auto check" light on the back of the 
flash should blink like the ready light does to indicate a good 
exposure.  No blink, something was wrong.  If the camera is in manual 
mode and the flash is in "normal auto" mode the flash will respond to 
its own internal sensor and flash the "auto check" light by itself 
without camera assistance.  In that case no film is required in the 
camera to do an exposure test since the TTL flash circuitry is not 
involved.  A test flash can also be made with the test button on the 
back of the flash.  If in "normal auto" mode the "auto check" light will 
blink if a good exposure was indicated.  When the flash is in manual 
mode the "auto check" can't be used since the flash has no indication of 
the aperture in use.

Dr. Flash






Tom Fenwick wrote:
> Nice one Piers.  I like that gentleman's pictures and thought someone ought
> to sort him out!
> Tom
> 
> 2008/11/20 Piers Hemy <piers@xxxxxxxx>
> 
>> Done
>>
>> -----Original Message-----
>> From: Tom Fenwick [mailto:super.wide@xxxxxxxxx]
>> Sent: 20 November 2008 10:53
>> To: Olympus Camera Discussion
>> Subject: [OM] Flash question on RFF
>>
>> One for you lot here:
>> http://www.rangefinderforum.com/forums/showthread.php?threadid=66456
>>
>> Tom
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