Re: Home made Lenses ( soft focus )

I have the Veritar instruction manual on PDF file if anyone would like a
copy...... It has unusual focusing properties unlike other Soft focus or
normal lenses and would be hard to figure out if you did not have the
insructions.......... I have never sent a PDF file so be patient...jc

----- Original Message -----
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: <alt-photo-process-l@skyway.usask.ca>
Sent: Monday, March 07, 2005 12:06 AM
Subject: Re: Home made Lenses ( soft focus )

>
> ----- Original Message -----
> From: "Michael Briggs" <MichaelBriggs@earthlink.net>
> To: <alt-photo-process-l@sask.usask.ca>
> Sent: Sunday, March 06, 2005 8:14 PM
> Subject: Re: Home made Lenses ( soft focus )
>
>
> >
> > On 04-Mar-2005 Tom Ferguson wrote:
> >>
> >> I've never seen a three element color corrected and
> >> coated Veritar! My
> >> 10 inch is two single uncoated elements with nothing but
> >> space and an
> >> alphax shutter between them.
> >
> >
> >> On Friday, March 4, 2005, at 11:33 AM, John Cremati
> >> wrote:
> >
> >>> Tom,
> >>> I believe the commercial Soft Focus Lenses go
> >>> far beyond the
> >>> mounting two or 3 diopter lenses in a barrel.... As a
> >>> example the lens
> >>> which
> >>> I had purchased is a color corrected Wollensak
> >>> Veritar. It is a 3
> >>> element design engineered to reduce chromatic
> >>> aberration , so it is
> >>> suitable for color. It achieves its softness by
> >>> controlled Spherical
> >>> aberration...
> >
> > The resolution is that the Veritar consists of 3 elements
> > in 2 groups. This
> > is what is shown in the cross-section view in an original
> > Wollensak brochure
> > that I have. The number of elements is confirmed by
> > shinning a flashlight at
> > the two groups: the front shows two reflections, while the
> > rear shows three.
> > There is more to the design of the Veritar than placing
> > two single-element
> > lenses on each side of the aperture. AFAIK, Wollensak
> > only used this design
> > for the Veritar. You can check yours with a flashlight --
> > unscrew the groups
> > from the shutter and count the reflections.
> >
> > --Michael
>
>
> This is interesting. Kingslake states that the Veritar and
> Verito were "simple uncorrected lenses similar to the
> Steinheil Periskop." Obviously, he was wrong about this.
> Its hard to know why the compounding was done. Perhaps for
> chromatic correction but it also may have been for other
> reasons. A cemented surface can be used to either correct or
> generate spherical aberration. A cemented doublet can also
> mimic the properties of some unavailable glass type.
> The more complex structure of these lenses helps to solve
> the puzzle of why they have such a unique reputation.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
>
>
>
>
> _____________________________________________________
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Received on Sun Mar 6 23:32:49 2005