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[OM] Re: Coverage angle of T-32, was: Vivitar 550FD M/P/O discussion

Subject: [OM] Re: Coverage angle of T-32, was: Vivitar 550FD M/P/O discussion
From: Moose <olymoose@xxxxxxxxxxxxxxx>
Date: Sat, 08 Jan 2005 14:13:40 -0800
OK folks,

You are busily comparing apples to donuts. Attributing the reported 
experience that the T32 covers the view of a 24mm lens to things like 24 
mm not being much wider than 28 mm and general bouncing around of light 
indoors, and whatever other excuses one can make for poor Oly is silly. 
Put your brains in thinking mode, assume the engineers at Oly were at 
least semi competent and the marketing guys were just like all marketing 
guys.

Do a little quick trig. The Angle of Views for lenses quoted in the eSIF 
are for the diagonal of the film frame, 43.3mm, not the long axis of 36mm.

For a 24mm lens, with spec. angle of view of 84 degrees, @ infinity:

              Film Dimensions
            --------------------
            Short   Long   Diag.
Frame        24      36    43.3
1/2 Fr.      12      18    21.6
Tangent     .50     .75    .90
1/2 Angle   26.6    36.9   42.0
AoV          53      74     84

In the upper portion of the eSIF, it states, " The coverage angle is 
almost equal to the picture angle of a 24mm super wide angle lens."

In the Specifications portion of the eSIF, it states. "Coverage angle: 
53° vertical, 74° horizontal (covers picture area of 24mm lens)."

In the Main Specifications portion of the T32 Instruction Manual, it 
states, "Coverage angle: 53° vertical, 74° horizontal"

Hmmm, like Horton, they said what they meant and meant what they said.

Now, the question of how much fall-off they allow in measuring coverage 
is still open, and we can continue to argrue, opinionate, prognosticate 
and maybe even test, that characteristic. Somebody got a blank white 
wall, T32, 24mm lens and some time on their hands? I think PS could 
stand in for the densitometer.

Moose



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