Selenium Light Meter

I have an old Weston Master V with Invercone and was wondering if it should
work with the Nikon D80. Is ASA the same as the newer ISO? I used to use the
meter with my Nikon F2A and it was great.

Bruce

"Bruce" wrote:

I have an old Weston Master V with Invercone and was wondering if it should
work with the Nikon D80. Is ASA the same as the newer ISO? I used to use the
meter with my Nikon F2A and it was great.


Yes, Bruce, ASA and ISO are the same and your Weston Master V will be
just as good for digital as film.

Incident light readings made using the Invercone are particularly
useful. If you have lost yours, they regularly come up on eBay or at
camera fairs.

Bruce wrote:

I have an old Weston Master V with Invercone and was wondering if it should
work with the Nikon D80. Is ASA the same as the newer ISO?

There's DIN, there is ASA and there is ISO:
DIN ASA ISO
... ... ...
21° 100 100/21°
24° 200 200/24°
27° 400 400/27°
30° 800 800/30°
... ... ...

DIN (1934) is based on the Schreiner-Grad of 1894, Schreiner-Grad
- 10 is the DIN number, e.g. 31° Sch == 21° DIN == 100 ASA ==
100/21° ISO.

ASA (1940ies) was changed in the 1960ies, ASA values before that
date are not really comparable with ASA values after that date.

ISO (ISO-5800:1987) simply combines the ASA and DIN values,
though oftentimes only the ASA part is quoted, so yes, the ASA
and ISO values are identical.

There's also GOST, Russian for "State Standard", which does have
the date of the norm (changed on 1987-01-01); the pre-1987 values
are ca. 90% of the ASA values (i.e. 100 ASA == 90 GOST, 1600 ASA ==
GOST 1400); the new values are identical with ASA.

There are also Weston (1930ies, i.e. pre-ASA), yes, from the
very same company that made your light meter, approx. ASA -
1/3rd stop (125 ASA == 100 Weston) , and GE (General Electric,
1940ies-1950ies) approx. ASA + 1/3rd stop (100 ASA == 125 Weston)

I used to use the meter with my Nikon F2A and it was great.

So the selenuim cell has probably not degraded too badly (they
don't age well).

Another thing to watch for is the difference between the ISO
ratings named on the camera and the real ISO ratings. I understand
from reading dpreview.com that Nikon DSLRs are quite close to it,
but that Canon DSLRs, at least the 20D and 30D, are actually
understating their speed by 1/3rd stop (i.e. ISO 3200 on the
camera == ISO 4000 real), though the 40D's speeds are close to
the real values.

-Wolfgang

On Sep 9, 6:42 pm, "Bruce" wrote:
I have an old Weston Master V with Invercone and was wondering if it should
work with the Nikon D80. Is ASA the same as the newer ISO? I used to use the
meter with my Nikon F2A and it was great.

Bruce


Though the Weston was the standard of the day, late 1950s and 1960s it
is an old light meter. Selenium cells are finicky don't know if I
would trust it over my camera meter. Frankly I have never seen a
Weston that works right, that goes back to the late 60's when I
started photography. All the used ones I have seen have had bad
cells.
Take the meter and the camera out and do test readings, digital is so
easy for this. ISO and ASA numbers should agree. See how the meter
agrees with the camera. Incident readings are very useful but have to
be done with the meter at the subject pointing to the camera, not
always the most convenient thing. If there is a discrepancy adjust the
meter's ISO, don't curse the camera. My Gossen Luna Pro had a half
stop discrepancy with my Canon F1 so I would set it on ISO 80 instead
of 64.

Tom

On Tue, 11 Sep 2007 05:51:26 -0700, tomm42 wrote:

Though the Weston was the standard of the day, late 1950s and 1960s it
is an old light meter. Selenium cells are finicky don't know if I
would trust it over my camera meter. Frankly I have never seen a
Weston that works right, that goes back to the late 60's when I
started photography. All the used ones I have seen have had bad
cells.

IIRC, even new, perfect selenium cells had to be used with care.
I recall instructions warning to keep them from being exposed to too
much light, as that could desensitize them and cause inaccurate
readings.

"ASAAR" wrote in message ...
On Tue, 11 Sep 2007 05:51:26 -0700, tomm42 wrote:

Though the Weston was the standard of the day, late 1950s and 1960s it
is an old light meter. Selenium cells are finicky don't know if I
would trust it over my camera meter. Frankly I have never seen a
Weston that works right, that goes back to the late 60's when I
started photography. All the used ones I have seen have had bad
cells.

IIRC, even new, perfect selenium cells had to be used with care.
I recall instructions warning to keep them from being exposed to too
much light, as that could desensitize them and cause inaccurate
readings.

As I recall, this was not a problem with selenium cells, but with CdS cells,
which did have a memory effect that made them troublesome. Also, unlike
selenium cells, the generally more sensitive CdS cells had color response
irregularities that made them sometimes inferior to selenium cells. CdS
became more popular due to compactness and the ease with which they
could be incorporated into camera bodies (plus their increased sensitivity).
In my experience, selenium-celled meters were quite durable, and I have
several models of Weston meters dating back to the late 1930s that still
work perfectly (and these even work well to moderately low light levels).
--
David Ruether

http://www.donferrario.com/ruether

On Tue, 11 Sep 2007 14:23:24 -0400, David Ruether wrote:

IIRC, even new, perfect selenium cells had to be used with care.
I recall instructions warning to keep them from being exposed to too
much light, as that could desensitize them and cause inaccurate
readings.

As I recall, this was not a problem with selenium cells, but with CdS cells,
which did have a memory effect that made them troublesome. Also, unlike
selenium cells, the generally more sensitive CdS cells had color response
irregularities that made them sometimes inferior to selenium cells. CdS
became more popular due to compactness and the ease with which they
could be incorporated into camera bodies (plus their increased sensitivity).
In my experience, selenium-celled meters were quite durable, and I have
several models of Weston meters dating back to the late 1930s that still
work perfectly (and these even work well to moderately low light levels).

Rats! I didn't RC, so thanks for the correction. Were there
several types of CdS cells? I vaguely recall ads or articles
mentioning "blue" CdS cells. I had two meters, a nice, small
Sekonic meter, followed by a (to my mind) bloated Gossen Luna Six.
At the risk of recalling incorrectly again, I assume that the meter
in my old Photomic T used CdS. Yes? No?

ASAAR wrote:

On Tue, 11 Sep 2007 14:23:24 -0400, David Ruether wrote:

IIRC, even new, perfect selenium cells had to be used with care.
I recall instructions warning to keep them from being exposed to too
much light, as that could desensitize them and cause inaccurate
readings.

As I recall, this was not a problem with selenium cells, but with CdS cells,
which did have a memory effect that made them troublesome. Also, unlike
selenium cells, the generally more sensitive CdS cells had color response
irregularities that made them sometimes inferior to selenium cells. CdS
became more popular due to compactness and the ease with which they
could be incorporated into camera bodies (plus their increased sensitivity).
In my experience, selenium-celled meters were quite durable, and I have
several models of Weston meters dating back to the late 1930s that still
work perfectly (and these even work well to moderately low light levels).

Rats! I didn't RC, so thanks for the correction. Were there
several types of CdS cells? I vaguely recall ads or articles
mentioning "blue" CdS cells. I had two meters, a nice, small
Sekonic meter, followed by a (to my mind) bloated Gossen Luna Six.
At the risk of recalling incorrectly again, I assume that the meter
in my old Photomic T used CdS. Yes? No?


For the avoidance of doubt, anyone interested in buying a Weston meter
should know that the above mentioned problems do not affect Weston
meters in any way. Obviously, an old Weston meter will have suffered
some deterioration in performance but all the major components can be
replaced.

Here in the UK, the Weston design of light meter was still
manufactured until a couple of years ago by Megatron Limited, branded
as the Euro MASTER II. I have one that was made in 2001, plus an
older one. They are extremely accurate and consistent meters, and
their large Invercone makes them especially suitable for reliable
incident light measurement. For those reasons they were the UK
wedding photographers' favourite light meter for several decades, and
many of us still use them (I also use a Gossen).

The Euro MASTER II is currently out of production but it and previous
UK-made Sangamo Weston designs can still be repaired by Megatron
Limited. To replace the selenium cell, the movement (the indicator
needle assembly) and re-calibrate and service the meter will cost only
GBP 66.00 including taxes and UK shipping. That's about US $140.00
and for that you get almost a whole new meter. Replacing just the
cell, plus re-calibration costs GBP 42.00.

http://www.megatron.co.uk/euromaster2/

According to ASAAR :

[ ... ]

Rats! I didn't RC, so thanks for the correction. Were there
several types of CdS cells? I vaguely recall ads or articles
mentioning "blue" CdS cells.

Those were "Silicon Blue" -- photovoltaic cells with no memory,
but which needed amplification. I still have a Gossen SBC LunaPro
meter, which I keep for the times when the built-in meter in my D70
can't be used (such as with AI lenses without chip modifications).

The CdS cells (Cadmium Sulfide) were photoresistors, which
required a battery and a meter, but no amplification. Those did have
the memory effect.

I had two meters, a nice, small
Sekonic meter, followed by a (to my mind) bloated Gossen Luna Six.
At the risk of recalling incorrectly again, I assume that the meter
in my old Photomic T used CdS. Yes? No?

Yes -- it used two of them on either side of the eyepiece to
maintain a balanced view of the image while metering it. I had to dig
into my old _Nikon-F/Nikkormat handbook of Photography_ to verify these
details, but the presence of mercury cells (PX-13) suggested that it was
CdS. Certainly there would not have been sufficient size to make a
sensitive Selenium cell in there (which would not have needed the
batteries), and I thought that it was too early to use the "Silicon Blue
Cells", and the electronics game was a bit short of long-lasting
amplifiers powered by the PX-13s. Even the Gossen LunaPro SBC needed
(and still needs) a 9V battery.

BTW -- I've had experience with Sekonic meters being less rugged
than the Gossen ones -- a bump and a magnetically held strip moves off
the magnetic pole pieces in the meter movement, changing the response of
the meter movement, and thus rendering its readings inaccurate. Of
course it happened when I was in another country for several weeks, so I
had to try to reposition it by eye (judging by the imprints left in the
lacquer) after disassembling it. I was not in a position to buy a new
meter -- and learn to use it from a manual written exclusively in
Spanish. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 12 Sep 2007 02:44:10 GMT, DoN. Nichols wrote:

I had two meters, a nice, small
Sekonic meter, followed by a (to my mind) bloated Gossen Luna Six.
At the risk of recalling incorrectly again, I assume that the meter
in my old Photomic T used CdS. Yes? No?

Yes -- it used two of them on either side of the eyepiece to
maintain a balanced view of the image while metering it. I had to dig
into my old _Nikon-F/Nikkormat handbook of Photography_ to verify these
details, but the presence of mercury cells (PX-13) suggested that it was
CdS. Certainly there would not have been sufficient size to make a
sensitive Selenium cell in there (which would not have needed the
batteries), and I thought that it was too early to use the "Silicon Blue
Cells", and the electronics game was a bit short of long-lasting
amplifiers powered by the PX-13s. Even the Gossen LunaPro SBC needed
(and still needs) a 9V battery.

Thanks for the followup. Try as I might to see that old gear as
unsophisticated and outdated, most of the memories are of how
enjoyable they were to use.