Re: Home made Lenses ( soft focus )

I agree that soft focus lenses are unique. Each model seems to do
something different :-)

I had never heard the term "Mechanical" versus "Chemical" focus. I
wonder if the "Chemical" isn't focus shift as you stop down. I've
always focused soft focus lenses ate the F/Stop I was going to shoot at
(I'm not sure where I was taught that).

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. My other Wollensak soft is a longer
Verito. Similar construction, but HUGE. About 4 inches by 7 inches in
size.

On Friday, March 4, 2005, at 11:33 AM, John Cremati wrote:

> 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!
>
>
>
> 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... Yet it is free from distortion....The lenses is also
> coated
> for added brilliance...... This lens is a mechanical focus type where
> what
> you see on the ground glass is what you get......A chemical focus lens
> is a
> lens that has to be back focused to compensate for what the film or
> process
> sees.......Sort of like shooting UV film... The film will see something
> different other than what is focused on...... Many of the SF lenses
> are of
> this design........
> The chromatic aberration control is achieved both by lens
> design as
> well as the actual raw material the lens is made of so they vary the
> diffractive index of the different glass lenses to bring the colors
> together.........
> A great book " Professional Portrait Lightings " by Charles Abel
> lists
> about 100 different portraits using various SF lenses..... The
> differences
> between the images are dramatic at times .... Of course the printing
> process is a big factor, lighting as well, but the lens differences are
> notable.....
> I agree, most of the SF lenses are very simple lenses with 2 or 3
> elements , but the effects of each manufactured lens are unique in the
> way
> they were engineered......
> John Cremati
>
>
--------------
Tom Ferguson
http://www.ferguson-photo-design.com
Received on Fri Mar 4 15:35:34 2005