[LargeFormat] Re: fresnels

[mark blackman]

A cheap source of a fresnel lens is a disused overhead projector. Take a
look in a skip/dumpster outside any office building, especially if it's
being re-fitted.


----- Original Message -----
From: "Skip Roessel" <skiproessel@mindspring.com>
To: <largeformat@f32.net>
Sent: Wednesday, January 22, 2003 3:04 AM
Subject: [LargeFormat] Re: fresnels


> As each little ring is cut with a slightly different angle to approximate
the
> rear surface of a condenser lens, making the master mould of a fresnel is
not
> too feasible in the home shop.  You need to visit your good friends at
Edmund
> Optics (www.edmundoptics.com) and pick one out.  I got a 16x20 fresnel for
my
> 7x17 banquet camera and mounted it over the existing glass on my Korona
with
> velcro.  Works great, image is as bright as can be, if you're lined up
while
> viewing it.  'Course if you move to one side everything disappears.
>
> They're all plastic, can be cut with a table saw, and are mounted outside
the
> ground glass, farthest from taking lens, so the GG depth remains true to
the
> film plane in the film holders. They scratch easily, though.  Anyone know
where
> I can get that non-scratch coating they put on plastic eyeglasses now?  I
put
> car wax on mine... better than nothing.
>
> Big fresnels are also found in overhead projectors, now crowding eBay for
$30.
> Here's one:
>
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=2302924199&category=25322
>
> If you buy one at auction, see if the seller will pop out the lens and
send it
> to you alone, scrap the rest rather than shipping a 30-pound machine to
you.
> skip
>
> skiproessel@mindspring.com
>
> Vincent Dobson wrote:
>
> > It is strange this thread started just as I am now in the process of
> > building a facility for CXXXXX Vision they are renting space from xyz
co.
> > xyz co did the inventing and R&D to develop machinery that injects
optical
> > plastic in molds to manufacture eyeglass lens. CV manufacturers and
markets
> > the machines to the labs.
> > Interesting process, but, expensive to develop, however once developed,
the
> > per unit cost is drastically reduced as compared to the labor intensive
> > method of taking a hockey puck size disk of plastic (or glass) and
grinding
> > down to a particular prescription.
> >
> > small world.
> >
> > Vince Dobson
> > Visions In Nature
> > www.VisionsInNature.com
> >
> > -----Original Message-----
> > From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net]On
> > Behalf Of Les Newcomer
> > Sent: Tuesday, January 21, 2003 4:50 PM
> > To: largeformat@f32.net
> > Subject: Re: [LargeFormat] a gritty day
> >
> > And that would be just to make the mould to inject the optical plastic!
> >
> > I think this thread started with ground glass for Speed Graphics and if
> > you want to use one for a  Speed you have to be a little careful where
you
> > put it.
> >
> > Most Anniversaries and Some Pacemaker Speeds did use fresnel or
"Ektalite
> > Field lenses" as Graflex called them.  The ground glass on a Speed is
> > loaded from the back, and if you installed a fresnel where there wasn't
> > one, you'll shift the ground glass out of position the thickness of the
> > fresnel.
> >
> > On Tuesday, January 21, 2003, at 01:28 PM, Vincent Dobson wrote:
> >
> > > hmm, The material the man is made of is from various keys on~~~~~~~~~
> > > oops,
> > > I guess you mean the fresnels?  The ones I have are made from a very
hard
> > > plastic, but this would not be a do it yourself project.  It takes a
very
> > > precision and expensive machine - think optical grade lathe and cost
mid
> > > 5
> > > to 6 figures I think.
> > >
> > >
> > >
> > > Vince Dobson
> > > Visions In Nature
> > > www.VisionsInNature.com
> > >
> > >
> > >
> > > -----Original Message-----
> > > From: largeformat-admin@f32.net [mailto:largeformat-admin@f32.net]On
> > > Behalf Of philip.lambert
> > > Sent: Tuesday, January 21, 2003 4:18 PM
> > > To: largeformat@f32.net
> > > Subject: Re: [LargeFormat] a gritty day
> > >
> > >
> > >
> > > ---
> > > From: "Vincent Dobson" <manitec@bellsouth.net>
> > > To: <largeformat@f32.net>
> > > Sent: Tuesday, January 21, 2003 7:52 PM
> > > Subject: RE: [LargeFormat] a gritty day
> > >
> > >
> > >> Very precise circular strokes. :)~~/~~~~!<
> > >
> > >
> > > Pardon me  -Is that a diagram or an oriental language?  And from what
> > > material
> > > do you make them?  PL
> > >
> > >
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