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  #21  
Old February 16th 11, 01:18 AM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning


wrote in message
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On 2/13/2011 3:22 PM, Richard Knoppow wrote:

However, the Geronar is a Cooke Triplet, a
three-element, air-apaced lens with no cemented surfaces.
Its of high quality and such lenses are capable of good
performance at moderate stops.


From my use, it's a very nice lens given a bad rap mainly
because it was sold at a low price as a "novice lens". Who
wants that when you can buy a pro lens? :P

It's multicoated, comes in a modern, reliable shutter and
is small/lightweight. It actually folds up in my super
graphic.

Given most LF lenses are used around f22, the wide open
edge performance isn't an issue for most people. I've
actually done some portraits with mine on 4X5 at f11 and
they look great. The only disadvantage I see with this
lens is the smaller image circle compared to the much
Larger/heavier/more expensive plasmat types. If I had to
choose this over some vintage lens that has questionable
coatings and flaky/ancient shutter, I would get this one
in a heartbeat.

Stephey

A carefully designed Triplet is capable of excellent
performance and Rodenstock is noted for making good lenses.
I am not sureprized it works well. Somewhere around f/22 is
the "optimum" stop for many LF lenses. The limit of a
Triplet is that they are hard to correct for either high
speed or wide angle, if it isn't required to be either it
can perform entirely satisfactorily.


--
--
Richard Knoppow
Los Angeles, CA, USA



  #22  
Old February 16th 11, 01:24 AM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning


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On 2/14/2011 8:52 PM, David Nebenzahl wrote:
On 2/14/2011 3:57 PM spake thus:

On 2/14/2011 2:32 PM, Thor Lancelot Simon wrote:

In ,
wrote:

From my use, it's a very nice lens given a bad rap
mainly because
it was sold at a low price as a "novice lens". Who
wants that
when you can buy a pro lens? :P

Well, at least in the 1990s when the question arose for
me, it was
more like "who wants that when you can buy a nice clean
used
Commercial Ektar"?

I actually replaced a "nice clean" commercial ektar of
the same length
with this lens and got much better results at my
shooting apertures of
f16-f22. Maybe my sample was a bad one but the geronar
has much higher
contrast and "snappyness" to the pictures, especially in
difficult
lighting. Add to that a much better shutter, I don't
think I'd want 50
year old lens with marginal coatings in one of those old
supermatic
shutters over this one.


What do you mean, "marginal coatings"? Do you think they
flake off or
something?

Sorry, but it sounds to me as if you've bought the
marketing hype hook,
line and sinker when it comes to "advanced, space-age"
coatings. The
only "marginal" here is that modren coatings are
marginally better than
the old ones. Hell, even *uncoated* lenses (horrors!) can
perform
extremely well (under certain conditions).




I guess you missed the "difficult lighting? And yes those
early coatings were good, just not as good as later ones.
And yes I do use uncoated lenses too so understand your
point here. In tough lighting the ektar created low
contrast chromes.

I didn't make this judgment based on marketing. I
wouldn't have bought a geronar at all if I wasn't having
issues with the commercial ektar of the same length. I
have a 135mm WF ektar and the images it makes are nice and
crisp compared to the ones I was getting with the comm
ektar, hence I looked for a replacement. I have never
considered replacing the 135mm WF ektar, it works just
fine so don't thing older coating are rubbish.

Sorry if posting that -in my experience- this "novice"
lens performs much better that my old commercial ektar
did- rocks the boat of people who are sold on those old
lenses are somehow some sort of religious experience. I
could see nothing wrong looking at the commercial ektar,
maybe it was a bad one? I can only base this on my
experience. It was a -sharp- lens but didn't have the
contrast/snappyness this geronar has. So to say "-Blank-
old lens is a better choice" didn't work out for me.

Stephey


Both the Geronar and Commercial Ektar have the same
number of glass-air surfaces, six. Neither is a high flare
lens even uncoated. Multiple coating does reduce flare and
has much better anti-flare properties for color than a
single coating. The effect is more for color purity and
saturation than for overall contrast.
While its possible the coatings account for the
difference I think something else must be happening. What I
suspect is that the cement in the rear element of the Ektar
may have become hazy. This is a peculiar effect that I've
seen in other Ektar lenses. When examined under
magnification, and using grazing incidence light, you can
see that the cement layer has developed a sort of
orange-peel texture. You can see it using transmitted light
as a light haze but its effect on contrast is enormous.
Check your Ektar for this.
FWIW, the Commercial Ektars were designed especially for
color work and are almost apochromatic. Kodak was using them
to promote the sale of color film.



--
Richard Knoppow
Los Angeles
WB6KBL



  #23  
Old February 16th 11, 05:09 PM posted to rec.photo.equipment.large-format
[email protected]
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Default Lens Cell Cleaning

On 2/15/2011 8:24 PM, Richard Knoppow wrote:

While its possible the coatings account for the
difference I think something else must be happening. What I
suspect is that the cement in the rear element of the Ektar
may have become hazy. This is a peculiar effect that I've
seen in other Ektar lenses. When examined under
magnification, and using grazing incidence light, you can
see that the cement layer has developed a sort of
orange-peel texture. You can see it using transmitted light
as a light haze but its effect on contrast is enormous.


I used the wrong term saying "marginal coatings", this was more what I
was referring to and since I sold this lens long ago, I have no way to
know what the actual problem was. The other issue I had was right after
purchase I had to have the old shutter repaired. Like I stated in
another post, I love my 135 WF ektar so it's not like I hate old lenses..

I guess what I was trying to get across is: in my experience this
"novice" lens produced MUCH better results, especially on color slide
film, than my commercial ektar did so some statement that one of these
old "classics" is always a better choice didn't pan out for me. Nor have
I seen anything in the results from this lens that would have me go look
for a replacement. Whatever was wrong with that ektar lens wasn't
obvious but I don't doubt there was likely something like you stated
wrong with it. Given their age, I also wouldn't doubt others have this
same issue, that doesn't sound easy or cheap to resolve. I would suspect
that finding a good working sample of a geronar would be more likely
that finding a good sample of a lens that is many years older, YMMV.

Stephey
  #24  
Old February 17th 11, 07:32 AM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning


wrote in message
...
On 2/15/2011 8:24 PM, Richard Knoppow wrote:

While its possible the coatings account for the
difference I think something else must be happening. What
I
suspect is that the cement in the rear element of the
Ektar
may have become hazy. This is a peculiar effect that I've
seen in other Ektar lenses. When examined under
magnification, and using grazing incidence light, you can
see that the cement layer has developed a sort of
orange-peel texture. You can see it using transmitted
light
as a light haze but its effect on contrast is enormous.


I used the wrong term saying "marginal coatings", this was
more what I was referring to and since I sold this lens
long ago, I have no way to know what the actual problem
was. The other issue I had was right after purchase I had
to have the old shutter repaired. Like I stated in another
post, I love my 135 WF ektar so it's not like I hate old
lenses..

I guess what I was trying to get across is: in my
experience this "novice" lens produced MUCH better
results, especially on color slide film, than my
commercial ektar did so some statement that one of these
old "classics" is always a better choice didn't pan out
for me. Nor have I seen anything in the results from this
lens that would have me go look for a replacement.
Whatever was wrong with that ektar lens wasn't obvious but
I don't doubt there was likely something like you stated
wrong with it. Given their age, I also wouldn't doubt
others have this same issue, that doesn't sound easy or
cheap to resolve. I would suspect that finding a good
working sample of a geronar would be more likely that
finding a good sample of a lens that is many years older,
YMMV.

Stephey


Well, results is what counts! It would be interesting
to know if the Ektar had something wrong with it. Coating in
general should not affect sharpness so but does affect
contrast and color purity and saturation, all of which are
interepreted by the eye as sharpness. OTOH, its possible
that this Geronal is just a better lens than the Commercial
Ektar you had.
If your Wide-Field Ektar has satisfactory contrast and
color rendering its a good indication that the problem with
the C-E was not the coating. The WF Ektar has the same
coating plus it has _four_ glass-air surfaces.


--
--
Richard Knoppow
Los Angeles, CA, USA



  #25  
Old February 17th 11, 05:23 PM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/17/2011 2:32 AM, Richard Knoppow wrote:
If your Wide-Field Ektar has satisfactory contrast and
color rendering its a good indication that the problem with
the C-E was not the coating. The WF Ektar has the same
coating plus it has _four_ glass-air surfaces.



That's true and I do use a LOT of cameras from that time period with
single coated and even uncoated lenses so I'm not sure what the issue was.

Another experience, I ran into the same sort of problem with a 135mm
xenar LF lens. It was a -horrible- lens where the 75mm xenar on my
rolleicord is a wonderful one. So just because a lens has more elements
in my experience doesn't mean it's always a better performer.

Stephe

  #27  
Old February 17th 11, 10:04 PM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning


wrote in message
...
On 2/17/2011 2:32 AM, Richard Knoppow wrote:
If your Wide-Field Ektar has satisfactory contrast
and
color rendering its a good indication that the problem
with
the C-E was not the coating. The WF Ektar has the same
coating plus it has _four_ glass-air surfaces.



That's true and I do use a LOT of cameras from that time
period with single coated and even uncoated lenses so I'm
not sure what the issue was.

Another experience, I ran into the same sort of problem
with a 135mm xenar LF lens. It was a -horrible- lens where
the 75mm xenar on my rolleicord is a wonderful one. So
just because a lens has more elements in my experience
doesn't mean it's always a better performer.

Stephe

I had a chance to test a 135mm, f4.5 Xenar as supplied
on some Speed Graphics, it had a problem similar to the
Wollensak Raptar/Optar in that while the center was quite
sharp the corners never got completely sharp even when
stopped down all the way. This problem seems to be uniform
throughout the Rapar/Optar line, including the enlarging
lenses, but not for the f/5.6 lens made for the Graflex
Super-D or the Wollensak telephoto lenses, both of which are
very good. I also have Rollei cameras with f/3.5 Xenars and
they are extremely sharp with good corner performance. All I
can think is that the same prescription was not used for
other focal lengths or for other speeds. Its very odd. So, I
don't know if you got a dog or if all of the Xenars are that
bad.
More elements give the designer more resources to make
corrections. The Cooke Triplet has six surfaces, two
spacings, and three powers, just enough to correct all seven
of the primary aberrations and maintain focal length. More
complex lenses allow for correction of secondary aberrations
so they are valuable where one needs a faster or wider angle
lens. Also, by using a symmetrical design the lateral
aberrations, lateral color, coma, geometrical distortion,
are, at least to some degree automatically corrected by the
symmetry.
While the Triplet is a simple lens it is _not_ cheap to
make because the element spacing is very critical so that
the mount has to be precision made.
The Tessar was not inspired by the Triplet but the
Heliar was. Hans Harting, of Voigtlander, tried to correct
some of the secondary aberrations of the Triplet by
compounding the two end elements. His original design was
not successful but later designers did much better. The
Voigtlander Heliar (which became a different design than
Harting's original), the Dalmeyer Pentac (of Booth), and the
Kodak Ektar used on the Medalist camera, and the Kodak
Enlarging Ektar lenses of 50mm and 75mm are examples of
excellent lenses based on this general design. However,
other lens types offer more possibilities to the designer so
the Heliar type has not been popular.


--
--
Richard Knoppow
Los Angeles, CA, USA



  #28  
Old February 18th 11, 03:11 AM posted to rec.photo.equipment.large-format
Thor Lancelot Simon
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Posts: 163
Default Lens Cell Cleaning

In article ,
wrote:

Another experience, I ran into the same sort of problem with a 135mm
xenar LF lens. It was a -horrible- lens where the 75mm xenar on my
rolleicord is a wonderful one. So just because a lens has more elements
in my experience doesn't mean it's always a better performer.


Most LF Xenars were "press" lenses, which really means budget: small
circle of coverage, never the best coatings (newspaper printing amps
up the contrast plenty), in some cases questionable quality control.
Schneider had a much higher-end series of lenses for similar applications,
the Xenotar. Perhaps this is has something to do with why the Xenars
are so uncharacteristically bad for Tessar formula lenses in those
lengths.

On the other hand, maybe it's not "uncharacteristic". Wollensak made
some awful Tessar lenses and so did a few others. Maybe Richard knows:
is there something about the Tessar design that makes is particularly
prone to manufacturing or Q/C error?

There are some truly awful Schneider large format lenses as well as some
very good ones. The 90 and 120mm Angulons in particular seem to have
been either misdesigned or systematically mismanufactured, while by
the time they started multicoating (for example, the earliest Symmar-S-MC
lenses) they seem to have gotten their act together.

The Schneider web site says they made the large-format Xenars until
the mid 1990s (this is a surprise to me). I wonder if the later ones
were any better.

--
Thor Lancelot Simon


"We cannot usually in social life pursue a single value or a single moral
aim, untroubled by the need to compromise with others." - H.L.A. Hart
  #29  
Old February 18th 11, 10:15 PM posted to rec.photo.equipment.large-format
Donn Cave
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Quoth (Thor Lancelot Simon):
....
| On the other hand, maybe it's not "uncharacteristic". Wollensak made
| some awful Tessar lenses and so did a few others. Maybe Richard knows:
| is there something about the Tessar design that makes is particularly
| prone to manufacturing or Q/C error?

I believe one way to make a Tessar awful is to use it for LF
applications that require a larger circle than it really delivers.

While comparing the reputations of various Tessars, it might be
interesting to correlate with the absolute coverage circle -
that's not the right word, I mean the farthest extent of any
kind of coverage, irrespective of optical quality. My hunch
is that identical glass could have a better or worse reputation
depending on artificial cutoff from its mounting etc.

I was always more interested in tonal rendering, something I used
to read about with various lens types though couldn't positively
pick out of my own results. It seemed to me for example that
my 20" Calumet-Ilex (Tessar type I believe) turned out better
on color negative film than a 10" WF Ektar or a MC 240mm Caltar-S.
Not a conspicuous difference at all, and I didn't get real
scientific about it, but enough that I would use the Calumet-Ilex
when I could.

Donn
  #30  
Old February 18th 11, 11:53 PM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
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On 2/18/2011 2:15 PM Donn Cave spake thus:

Quoth (Thor Lancelot Simon):
...
| On the other hand, maybe it's not "uncharacteristic". Wollensak made
| some awful Tessar lenses and so did a few others. Maybe Richard knows:
| is there something about the Tessar design that makes is particularly
| prone to manufacturing or Q/C error?

I believe one way to make a Tessar awful is to use it for LF
applications that require a larger circle than it really delivers.

While comparing the reputations of various Tessars, it might be
interesting to correlate with the absolute coverage circle -
that's not the right word, I mean the farthest extent of any
kind of coverage, irrespective of optical quality. My hunch
is that identical glass could have a better or worse reputation
depending on artificial cutoff from its mounting etc.


Interesting you should mention coverage as it relates to Tessars.

Some time ago I did an experiment (a successful one as it turned out)
with a Tessar that was "too short" for the format. Not sure it qualifies
as LF, but I was shooting 9x12 (cm) film with the "next smaller size"
lens, a 105mm (made for 6x9) instead of the usual 135mm or so. (The lens
was a Carl Zeiss Jena f/4.5 Tessar).

It covered beautifully, sharp and tasty looking from corner to corner.
Not an extreme example, I'll grant you: the 9x12 image circle is 150 mm
(nominal), while the 6x9 is 110 mm. And I believe that these older,
uncoated lenses are exceptionally well-made, high-quality examples of
the species.


--
The phrase "jump the shark" itself jumped the shark about a decade ago.

- Usenet
 




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