Hi Larry - only early versions of the Leitz 50/2 Summicron Collapsible
(M39) are "hot."
Eric Goldstein
On Sun, Mar 8, 2020 at 2:15 PM Laurence Segil <ljsegil@xxxxxxxxx> wrote:
---
Lanthanum is not a radioactive element except for a rare <.1% abundance
isotope. However, Thorium, an Actinide element rather than a Lanthanide was
also used to create glasses with high refractive indices and low dispersion
and was used in some photographic lenses manufactured following WWII. Some
of the lenses that used Thorium glass include the Voigtlander Apo-Lanthars
for large format cameras, the Kodak Aero-Ektar, the Leitz 50/2 Summicron
Collapsible, and some of the Asahi Super Takamur lenses and these do have
radioactivity levels that are detectable above baseline and frequently show
yellowing of some of the glass elements.
Larry Segil
On Sat, Mar 7, 2020 at 3:34 PM Eric Goldstein <egoldste@xxxxxxxxx> wrote:
I can't say if the Ektars used so-called "rare earth" glass. Many of
the fast lenses of that period that did used Lanthanum glass, which
was pretty much the only rare earth glass then available at a
reasonable price and quantity. They are "hot (radioactive)." The
famous Aero Ektar 178mm f/2.5, that is now considered a jewel among
photographers and very expensive on the resale market, is "hot" and
subject to yellowing. My first production run M39 Summicron f/2 is
also hot and somewhat yellowed. Some fast Super Takumars, early Zeiss
Pancolor "Zebras" and others from the 60s are also yellowed due to
this. These lenses can usually be cleared by exposure to UV light...
either strong sunlight, or some use cheap Ikea LED desk lamps that
apparently have a good deal of UV.
Since Ektars don't yellow, I'm thinking they don't have rare earth
elements, or at least not Lanthanum.
Goodness how far we have strayed.
Eric Goldstein
On Sat, Mar 7, 2020 at 3:40 PM `Richard Knoppow <dickburk@xxxxxxxxxxxxx>
wrote:
---
I think the Ektars also used rare earth glasses. All of the
Ektar series were designed for color photography because Kodak
was promoting color films. While most are conventional designs
they are very nearly apochromatic especially the Commercial Ektar
made for LF cameras. The original Tessar was an f/6.3 lens. While
much work was done on increasing the speed it seems still to be
about optimum. Kodak did, however, make a 12", f/4.5 Ektar,
intended mainly for use with slow Kodachrome. I have a set of
cells but no shutter or barrel for them.
Graflex used Zeiss Tessars on Speed Graphics for a couple of
decades until WW-2 made them unavailable (along with Compur
shutters). They then switched to Kodak Ektars. While the Tessar
was a very good lens the Ektar is noticeably sharper,
particularly in the rendition of fine textures. However, the
uncoated Ektar has a flare spot from bright objects near the
center of the field which the Tessar does not. The coated version
of the Ektar does not have the spot.
Of course every lens maker made some version of the Tessar
with widely varying quality. My experience with the Wollensak
Raptar, as used on some post war Speed Graphics, is that they are
awful lenses.
On 3/7/2020 10:36 AM, Eric Goldstein wrote:
Yes, you're right... the Ektar 101 is f/4.5 and the 127 is f/4.7
Part of the reason these Ektars may perform so well is that these
apertures are pretty much the design speed of a tessar-type at these
image circles. f/3.5 for a 69 tessar-type is aspirational, especially
for front cell focusers, and f/2.8 has got to be pretty compromised.
But larger negatives meant less enlargement, so less critical..
Eric Goldstein
--
On Sat, Mar 7, 2020 at 12:02 PM `Richard Knoppow
<dickburk@xxxxxxxxxxxxx> wrote:
The 101mm Ektar is one of the best of the series. I think it---
is f/4.5 not 4.7. The 127mm version, found on 4x5 Graphics, is
f/4.7 because of the limitation imposed by the clear aperture of
the shutter, it is the same design. Another lens used on the baby
Graphic is the 105mm, f/3.7 Ektar. It is a modified Heliar
design. It is similar, if not identical, to the lens used on the
Kodak Medalist camera. A similar design was also used for some
Kodak enlarging lenses. The design is by Fred Altman of Kodak.
The patent is interesting and worth reading.
USP 2,279,384 It is an astonishingly sharp lens and nearly
apochromatic.
On 3/7/2020 4:48 AM, Eric Goldstein wrote:
Agreed. They don't have the image quality of my Baby Speed with Ektar--
101/4.7 and 69 back. But they are much more compact, lighter, and the
lens is a stop faster.
The gold standard of the vintage 69 folders is the Bessa II w/Heliar I
think but they are ridiculously expensive. The Bessa IIs with Color
Skopar are not that much less expensive. The 105/3.7 Ektar on a Baby
Speed is as fine or better a performer than these two, but again the
size disadvantage is in play.
Eric Goldstein
--
On Sat, Mar 7, 2020 at 5:53 AM David Stumpp <photos@xxxxxxxxxxxxxxx>
wrote (snipped):
I do love these 6x9 cameras for their size and weight and their---
relatively good image quality, but, in terms of image quality, none
of them have an edge on my Fujica 690. If not for that camera’s
weight, I’d carry it a lot more.
Rollei List
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--
Richard Knoppow
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WB6KBL
---
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