Hello Richard:
Very interesting your explanation about glasses
refraction index and dispersion.
The way UV rays affect color films and B&W films is a bit different, UV
rays affect the B&W image contrast mainly and they affect color tints and
contrast on color films. Rollei had two different UV filters for the TLR:
The UV filter for B&W and the H1 UV filter for color photography, Rollei
explained its UV filter was for B&W only, otherwise it could affect the
colors.
The Rollei Practical accessories brochure says: "UV (filter): High
altitudes above 6000 feet. Seascapes. Eliminates ultra-violet rays which
reduce contrast."
"H1 (filter) UV.filter especially designed for long distance color
photography. Absorbs ultra-violet rays, subdues predominance of blue and
cuts aerial haze in distance shots". Both are UV filters but different
according you use B&W film or Color film. The best filters for long
distance B"%W photography are the Orange and the Light Red.-
Carlos:
El dom., 7 jun. 2020 a las 17:13, `Richard Knoppow (<dickburk@xxxxxxxxxxxxx>)
escribió:
The use of UV filters goes way back before high index glass.
They were recommended for color photography in the mountains
where there was lots of UV. UV also affects B&W films. Glass
varies a lot in its transmission of UV. A simple way to test is
to use a UV grow light and see how much it makes paper or laundry
washed with brighteners glow. Then put some ordinary window glass
between the lamp and the test surface. Most glass will cut down
the amount of UV considerably. Some lenses have cement that is a
pretty effective UV filter. I don't remember how if Canada
Balsam, used as an optical cement before about the 1950s passed
UV or not.
Note that glass has two fundamental properties that are
vital to lens design: index of refraction, and dispersion. It is
the range of dispersion available with different indices of
refraction that makes the difference in the "old" and "new" or
"Jenna" glass. Modern (well they are now seventy years old) rare
earth glasses have an even wider range of dispersion. The idea is
that glass with a high index of refraction but relatively little
dispersion can be used to simplify the achromatizing of lenses.
On 6/7/2020 10:06 AM, CarlosMFreaza wrote:
Hi Ferdi:
Yes: "From September 1968: Nr. 3.082.000: UV
depletion layer", your camera's Tessar was already made with
the special cement.
Rollei recommended to use the H1 filter with the TLR Tessar and
Xenar lenses for colour photography due to the UV rays issue ;
BTW, it is not a dramatic or fundamental thing, I obtained very
good colour photographs with my 'cord IV Xenar without filters;
sometimes, according the hour and natural lighting , large
water surfaces could get an unnatural and rare blue- violet
tint due to the UV rays, I have a couple of samples with the
Xenar. Anyway, almost any standard lens requires UV filter for
the high mountain due to the UV radiation excess.
The Kodak Ultramax 400 belongs to the Gold family, they are
consumer films with medium to high saturated colors, general
public like them, you can also increase colours saturation
using a slight underexposure. Thanks for your opinion.
Carlos
El dom., 7 de jun. de 2020 10:34, F.W. Stutterheim
<dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx>> escribió:
Hi Carlos,
Time to check my Rollei 35 cameras and Prochnow's book. The
'UV-Sperrschicht' was used from camera number 3082000. My
chrome one bares #3092xxx so it seems I am in the clear. My
black one has no number. The dented top cover was replaced
for a new one before I got it but its lens number is quite
a bit higher so I can assume this one is also post
September 1968.
I suppose the name Ultramax suggests high saturatation?
Nice beach scene Carlos.
Best regards,
Ferdi.
----
Ferdi Stutterheim,
Drachten, Netherlands.
Op 6 jun. 2020, om 11:44 heeft CarlosMFreaza
<cmfreaza@xxxxxxxxx <mailto:cmfreaza@xxxxxxxxx>> het
volgende geschreven:
The Tessar type lenses does not require high-index glasses
(Claus Prochnow "Rollei 35, eine Kamera-Geschichte", page
41), it caused the firsts Tessar 3,5/40 lenses made by
Carl Zeiss for the Rollei 35 made in Germany from November
1966 up to September 1968 transmitted so much UV radiation
that an UV filter was necessary under certain lighting
conditions; Carl Zeiss solved the problem using an UV-
absorbing special cement from September 1968; Rollei 35
cameras made in Singapore ( production started there at
the ending of 1971) with the Tessar made by Rollei under
CZ license never had the UV problem.
This photograph was taken some years ago with the Rollei
35 Tessar (made by Rollei) , Kodak Ultramax 400 color
negative film:
https://flic.kr/p/2j9a5M2
Carlos
--
Richard Knoppow
dickburk@xxxxxxxxxxxxx
WB6KBL
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