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[OM] Re: Question

Subject: [OM] Re: Question
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxx>
Date: Thu, 28 Apr 2005 08:05:37 -0400
Ali wrote:
> As I mentioned in a previous post...I took some photos in an auditorium. 
> Used 200 speed film in my OM-2S w/ 35-70 f3.6 lens and T-32 mounted on a 
> PBG2. Photos came out a bit dark...part of the problem is that I think I 
> had the flash pointed upward a bit too much. Should I use the T-32 flash 
> adapter next time - I noticed the adapter starts @ 50. Does this mean 
> that even while using a standard 50mm lens I should consider using the 
> flash adapter?
---------------------------------
The T-32 is supposed to cover the angle of view of a 24mm lens.  If 
you're using a 50mm lens the area of coverage is only 1/4 that of a 24mm 
lens.  Using the zoom adapter will narrow the beam angle from the flash 
and yield a higher guide number.

Now comes the tricky part.  The guide number and angle of coverage are 
only meaningful for direct flash.  If you're trying to bounce off a 10 
meter high ceiling at a subject 10 meters away the actual distance to 
the subject (for the light beam) is over 22 meters.  To further 
complicate matters, the surface you're bouncing from is likely absorbing 
a very large percentage of the light.

If you're shooting with manual flash you have no hope of getting this 
right without a meter.  If you're shooting TTL flash the camera *may* be 
able to measure it properly but there may not be enough light left for a 
proper expousre.  If that's the case then using the zoom adapter may put 
you back in business by not scattering so much light.  Also, if you're 
bouncing the light, the beam has more distance to be able to spread out 
and the area being covered is wider than if shot straight on.  In the 
case outlined above, where the bounce distance is more than double the 
subject distance it might be best to choose a 75 or even 100mm setting 
on the zoom adapter even though you are actaully shooting with the 50mm 
lens.  This will conserve as much light as possible while still covering 
the full angle that the camera sees.

Without some means of lighting the background, however, the subject may 
be properly exposed but the background will go dark.  If you were 
shooting TTL flash with the 3Ti and had the camera mounted on a tripod 
you could "drag the shutter" by using a slower than 1/60th shutter 
speed.  This would capture the background in what is essentially a 
second exposure.  Leaving it a stop or two down from the correct 
exposure will still be an improvement over a black tunnel.  But only the 
3Ti can this.  All the other TTL flash capable cameras must be run in 
auto mode for TTL flash and the shutter will be restricted to 1/60th.

Chuck Norcutt


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