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Re: [OM] Exposure compensation [2]

Subject: Re: [OM] Exposure compensation [2]
From: David Irisarri Vila <valicors@xxxxxxxxxx>
Date: Sat, 23 May 1998 14:56:42 +0200
C.H.Ling escribió:

> ----------
> > From: David Irisarri Vila <valicors@xxxxxxxxxx>
> > To: Olympus Questions <olympus@xxxxxxxxxxxxxxx>
> > Subject: [OM] Exposure compensation
> > Date: Saturday, May 23, 1998 2:44 PM
> >
> > When the  background  is  darker than the subject, what
> > happens with shutter control?
> > 1. The flash intensity is reduced.
> > 2. The flash intensity is always the same but  the  shutter is opened
> > more time in order to capture the background, reducing the speed with
> > danger of handshaking.
>
> With camera in auto mode, shutter is always locked at 1/60s with OM
> flashes. Camera will be operated at TTL flash mode (average meter the film
> plan reflection).

Then if you see through the viewfinder and see (ie. 1/8s), you  don´t
have to be panic because the shutter is locked at 1/60s. Then, I can´t
understand the OTF system, because  when  you shoot  with  flash  you 
can  meter  the exact light comming to the surface of the film. Then, 
the  shutter  must  control the speed increasing or decreasing as
needed, don´t you?

What does mean sync 1/60 or slower? If I want to fire at 1/15 with
flash, I must put the camera in manual mode???

> > Would be a good idea to spot a value from the face of the subject
> > (ie. 1/8s) and to take another value from the deep background (ie. 1/2s)
> > and after clear the values from the memory and put -2 exp values in
> > the exposure compensation dial and fire with flash?
> >
>
> Put in your mind that the camera will measure the flash light reflected to
> the sensor. The following factors will affect the light reflection:
>
> 1. The color of your object (for example the color of the clothes).
> 2. The color of the background.
> 3. The flash-object to flash-background distance ratio.
> 4. The ize of your object occupied the whole frame.

So, I would be a good idea to shoot with 100mm, having a good working
distance in order to enhance the background light. I have problems with
this because I use a Zuiko 50mm/f1.2, don´t you?

> So object to background light ratio at ambient light condition may not be
> good enough for you to make the judgment on the compensation needed.
>
> To be more accurate, you need a flash meter or use GN-distance calculation.
> But when using GN-distance calculation please have a check on the actual
> power of your flash. I have four OM flashes, they are all more than one
> stop under the quoted values. (I measured with a Sekonic L-328, I have
> double checked the flash meter with a gray
> card+OM4T+100mm/f2+T32+Fujichrome 100D in TTL mode, it is within one stop
> error).
>

Could you please explain me what is GN-distance? 

Best regards 

Dave    
> It is not only happen on my OM flashes, a Nissin flash I owned in the pass
> was also the same. I just wonder how they measure the GN values.
>
> C.H.Ling
> Hong Kong
>
> > Please I would be very pleased if somebody could help me with this.
> >
> > Best regards
> >
> > Dave
> >
>
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