Re: Home made Lenses ( soft focus )

----- Original Message -----
From: "Tom Ferguson" <tomf2468@pipeline.com>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, March 04, 2005 8:50 AM
Subject: Re: Home made Lenses ( soft focus )

>I own three "real" soft focus lenses. Two old Wollensaks
>and a more modern Fuji. The Wollensaks were bought before
>the current pricing madness (I think I paid about $125US
>each for my 10 inch and 16 inch, both in shutter!).
>
> The older soft focus lenses, like my/your Wollensak
> Veritars, are really just a couple diopters. Very simple
> two element lenses. A diopter is simply a single lens
> element. This, given the current pricing madness, is the
> joy of John's article. They are simple and cheap to build!
>
> The more modern Fuji soft focus lens is a different beast.
> Nice in its own way, but a far more complicated lens
> formula. I find myself using the old (simple) Wollensaks
> far more often.
>
> Actually, my favorite soft focus lens is a "mystery lens"
> bought at a swap meet (Quarksite in the Arizona desert).
> It was sold as a "Real Kodak Large Format lens", but has
> no markings and doesn't cover 4x5 at infinity. Two
> elements, no shutter. You can see images made by it here
> (kalli on cloth):
> http://www.ferguson-photo-design.com/toysportfolio.html
>
   I don't want to be picky but the meaning of diopter is
not a single lens element. A diopter is a unit of focal
length defined as 1/FL in meters, i.e., a lens of 1 diopter
has a focal length of 1 meter. Diopter measurement is useful
where a lens is used primarily in combination with another
lens as in spectacle lenses or close up lenses for cameras.
The reason is that the combined focal length of two leneses
is 1/(( 1/A + 1/B) - 1/D) where A and B are the focal
lengths of the two lenses and D is the distance between
them.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com