[pure-silver] Re: Chromatic Aberration of Enlarging Lenses
- From: Georges Giralt <georges.giralt@xxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Thu, 27 Apr 2006 11:34:04 +0200
Hi !
I have used a "Saphir Boyer" f:3.5 of 75 mm focal lenght.
It was a 4 lens design French made just post WWII. Massive lens in brass with a
impressive F stop made of more than 20 blades (from memory).
I was unable to have a sharp print in color, all my 6x6 Ciba were blurry, but
the lens performed well in B&W, using MGIV paper.
I sold the lens and bought a Nikon. Never had a blurry color print (although I
do not print color anymore...)
I own the Peak focuser with the blue filter. I can't see any difference in focus
with or whitout the filter. But my eyes are poor, so it may just be me...
I've tested it with my Laborator 1000 condenser enlarger with my Nikon f:2.8 50
mm, f:2.8 63 mm, f:5.6 105 mm, Computar f4.5 80 mm, and Rodagon f:5.6 150 mm
bought either second hand or new. I do not expect to own so perfect and good
lenses to be optically defect free. So I wonder if the lens designs are at
fault here. I think current 6 lenses design, multi coated from a reputable
manufacturer are resonably perfect. (well as perfect as money can buy).
I think that when color printing has become widespread, lenses began to be
corrected from color aberrations, and so the problem Ctein saw is not one have
to bother with today.
Just my 2 cents here.
Selon Tim Rudman <tim@xxxxxxxxxxxxxxx>:
>
> My Peak focus finder has a blue filter for this reason. I was never
> convinced that it made any visible difference. I know others who dismiss the
> idea (in print) and some who swear by it.
> Tim
>
> -----Original Message-----
> From: pure-silver-bounce@xxxxxxxxxxxxx
> [mailto:pure-silver-bounce@xxxxxxxxxxxxx] On Behalf Of Steve Nicholls
> Sent: 27 April 2006 03:17
> To: pure-silver@xxxxxxxxxxxxx
> Subject: [pure-silver] Re: Chromatic Aberration of Enlarging Lenses
>
> Richard Knoppow wrote:
> > Quite some time ago Ctein wrote that he had discovered that visual
> > focusing of enlarging lenses resulted in blur due to chromatic
> > aberration. He blamed it on the UV part of the spectrum. I was one of
> > those who poo-poo-ed the idea. Maybe not. I found the following in a
> > Kodak booklet entitled _Use Maintenance, and Repair of Professional
> > Equipment_ which is included in the _Kodak Professional Handbook_
> > dated 1952. The particular section is on the maintenance of the Kodak
> > Auto-Focus Enlarger, Model E. This is a 5x7 enlarger which looks
> > something like the Elwood but uses a different method of auto focusing.
> > "These enlargers have been shipped with two types of lenses, the
> > Kodak Anastigmat No.33 f/4.5--7.5 inch, and the Eastman Projection
> > Anastigmat f/4.5--7.5 inch. In the case of elnargers fitted with the
> > No.33 lens, correct focus may be determined by photographic means, but
> > not visually, because there is a difference between the photogaphic
> > and visual focus."
--
=============================================================================================================
To unsubscribe from this list, go to www.freelists.org and logon to your
account (the same e-mail address and password you set-up when you subscribed,)
and unsubscribe from there.
Other related posts:
