[pure-silver] Re: making smaller prints with 8x10 enlarger
- From: Leigh Solland <solland@xxxxxxxxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 13 Oct 2004 21:08:30 -0600
Ryuji Suzuki wrote:
> With telephoto lenses, back focus is shorter than the focal length.
> Non-telephoto lenses of long focal lengths do not have this property.
>
> Opposite of short lenses and inverse telephoto (or retrofocus, which
> is Angenieux name for inverse telephoto).
>
Peter De Smidt wrote:
> A longer lens is simply a lens with a longer focal length. A telephoto
> lens is a lens, of whatever focal length, which focuses with less
> extension than it's focal length would indicate. For example, a lens
> with a focal length of 12 inches needs roughly to be 12 inches from the
> nodal point of the lens to the film plane to be focused at infinity. A
> telephoto design of the same focal length might be able to focus on
> infinity with only 9 inches from the nodal point of the lens to the
> negative plane.
>
Thanks to both of you. I learned something today.
Leigh
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