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Re: [OM] Auto Exposure on OM4T(Long)

Subject: Re: [OM] Auto Exposure on OM4T(Long)
From: frieder.faig@xxxxxxxxxxxxxxxxxxxxxxxxx
Date: Wed, 1 May 2002 22:17:54 +0200
On Thu, Apr 25, 2002 at 11:00:47AM -0700, Winsor Crosby wrote:
> >
> >
> >Film reflectance is a issue for testing guy`s but not for practical work.
> >The difference it nomimnal and real film-sensivity already outweight
> >  this problem.
> >
> >Frieder Faig
> 
> That is not really true. If you consult the archives as I just did 
> you will find discussion of this issue. Before Gary Reese did his OM 
> lens tests he also measured the reflectance of various films and 
> found at least a 1 stop difference, if I remember correctly, between 
> the highest and lowest.

My statement is based on meassurements published  in a photo 
magazine in 1979 when testing the OM2n.
The min-max differences were:
  slide films:  +0.4 ..-0.2 stops
  print films: +0.2 .. -0.2 stops
  b&w: +0.2 .. -0.3 stops
  high contrast copy film: +0.8 stops

With one exeception all film-types don`t differ more than 0.6 stops, 
wich is +/- 1° ISO difference.
The differences between slide-film-reflectance  in Gary`s test were
 within the 0.5 stops area. The print-film differ more, But they also
 have more lattitude.

When I`m concerned about exposure differences in the 0.3 stops
area, I`m using spot metering anyway, and not average metering.
And you need self tested film type dependant iso-setting for this
accurancy at all. I don`t worry about film-reflectance.

Frieder Faig 

 

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