----- Original Message -----
From: "Giles" <cnocbui@xxxxxxxxxxxxx>
To: <olympus@xxxxxxxxxxxxxxx>
Sent: Friday, September 15, 2000 2:01 AM
Subject: Re: [OM] A-200 teleconverter
>
> I think it has to do with whether your teleconverter goes in front of the
> lens or behind it. ;-)
>
> Giles
Correct Giles. This is the info I have:
A conventional behind-the-lens converter altering the focal length of the
prime lens affects the light *after* the limitation of the lens aperture.
With front-mounted converters, the focal length of the prime lens is also
altered by the afocal supplementary, but this is all done *before* the lens
aperture, so does not affect the amount of light reaching the film. The same
should be true of focal auxiliaries such as close-up lenses (but what about
the close focus being affected then?)
A front mounted afocal telephoto can also be referred to as a Galilean
telescope (positive lens near the subject, negative near the lens); the wide
attachment is a reverse Galilean telescope (negative front, positive rear).
Dearly hoping this was of some help ;-)
Per Nordenberg
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