[LargeFormat] Bad Kodak Lens

[Richard Knoppow]

----- Original Message ----- 
From: "Richard Knoppow" <dickburk@ix.netcom.com>
To: "Large Format List" <largeformat@f32.net>
Sent: Saturday, March 13, 2004 5:50 PM
Subject: [LargeFormat] Bad Kodak Lens


>   After having touted Kodak lenses for some years I've
> finally encountered a bad one. This is a 101mm, f/4.5 lens
> for a Miniature Speed Graphic. The particular lens was
built
> in 1941. The problem is excessive spherical aberration.
This
> results in enough focus shift to prevent setting up the
lens
> with a rangefinder. In fact, it was repeated rangefinder
> errors that tipped me off to what was happening. Other
Kodak
> Ektars I have are all very sharp and have virtually no
> spherical. I've checked this lens for tightness, etc., and
> it seems fine.  I bought this lens some time ago to
> refurbish a Miniature Speed Graphic I was given by a
friend.
> The original lens, a Wollensak Optar, was pitted, probably
> from moisture in storage. The pitting is quite deep and
> results in scattering and haze. However, the image is
still
> good enough to get some idea of the original performance.
> Surprize! It must have been excellent. The lens shows no
> sigh of softness when wide open (except from the pitting)
> and has no detectible focus shift. This has caused me to
> re-evaluate my opinions of both Wollensak and Kodak. I
have
> other Wollensak lenses which are excellent performers but
> have encountered some real dogs. This Kodak lens is the
> first Kodak dog I've seen.
>   I've seen reference to some Kodak lenses having shims in
> them. I've never seen one but its possible. The excess
> spherical in this lens _could_ be caused by improper
element
> spacing. However, the lens was hazy when I got it and
there
> was no sign that it had ever been opened. Maybe not.
>   In any case, I will be on the look out for another lens
> for this camera and will consider Optars as well as Ektars
> this time. I will also play around this this lens to see
if
> I can improve its performance. My other Kodak Ektars,
> including a 127mm of the same age, are outstanding lenses,
> so this guy is a bit puzzling, especially as it is in a
> Kodak shutter marked Graphic so it must have been on a
mini
> Speed Graphic originally and gone through the Graflex
plant.
>    I had an interesting adventure restoring this camera,
> which was in awful condition. I will post some more later
on
> repairing Kalart rangefinders and some things I found out
> about this camera.
>
> ---
> Richard Knoppow
> Los Angeles, CA, USA
> dickburk@ix.netcom.com
>
>
   Later. I may have fallen into a trap I should have
thought of. I just could not believe this lens could be this
bad so I tried a couple of things. Mainly removing and
reinstalling the front element, making certain it was seated
correctly and that the retaining ring was really tight. I
also made sure both cells were seated and tight. That seems
to have fixed the problem. I will know better tomorrow when
I can test in daylight with a distant object. I thought at
one point that I actually saw the thing change focus while
setting up the rangefinder. If this problem is gone tomorrow
it will be a good object lesson on just how sensitive to
spacing lens elements are.

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