sandro Posted February 4, 2012 Share #1 Posted February 4, 2012 Advertisement (gone after registration) I am looking for information on the history of lightmeters in general, not Leica meters. Like when selenium meters were introduced, since when CdS meters came into existence etc. Is there a website or booktitle that someone can mention? Thanks a lot, Lex Quote Link to post Share on other sites More sharing options...
Advertisement Posted February 4, 2012 Posted February 4, 2012 Hi sandro, Take a look here Light meter history. I'm sure you'll find what you were looking for!
pico Posted February 4, 2012 Share #2 Posted February 4, 2012 (edited) Look to the history of extinction meters. I have a few but they have all degraded so that they are useless. If you want to go way back, the most novel light meter (however not the best) I've seen is one which is a horizontal strip with drawings of the eye's iris at various constrictions across it with a number below each and a horizontal mirror to look at one's own eyes, and the scene beyond, and below a suggested F-Stop at a given shutter speed based upon the constriction of the viewers pupils. Strange. Really odd. Edited February 4, 2012 by pico Quote Link to post Share on other sites More sharing options...
jc_braconi Posted February 4, 2012 Share #3 Posted February 4, 2012 history light meters Light meter - Wikipedia, the free encyclopedia Light meter - Camerapedia Lex You can start with these and who knows where you'll arrive ....the web is a huge space Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted February 4, 2012 Share #4 Posted February 4, 2012 Selenium meters were introduced about 1934, the Weston brand being popular in the U.S. Gossen became active in Europe in the late 1930's with their Sixtus brand. Because of the large cell needed to produce current enough for a microammeter, they could be used only for hand meters and in not TTL measuring types built into cameras. Cameras with built-in meters had a cell window in front and a meter needle in a window in the top plate; microammeters of the 1930's to 1950's were too large to be built into finders. The photocell voltage was used directly as input to the ammeter, so no battery was needed. CdS (cadmium suphide) cells came in around 1960 and the cells were so small that you could build one into the meter prism of an SLR camera. The CdS cell is a photoresistor, and does not generate any current. This comes from a battery which must have a precise and steady output as this is used as a reference for the whole system. The CdS cell lets through more or less current to the ammeter, depending on how much light falls on it. Wrong battery, wrong readout. Leica M cameras had the problem that there was no matte screen to meter against. The M5 solved this by mounting the cell on the end of a swing-up 'paddle' in front of the shutter; this swung down before the exposure. Another problem was where to put the bulky ammeter. Early prototypes from the middle of the 1960's has a readout window on top of the camera. But a semi-spot meter combined with a readout that required you to remove the camera from your eye, so that you could not see what the camera was actually metering, was a recipe for exposure disaster. The project was shelved in favour of an updated camera – the M4 – with a better (CdS) Leicameter. It was revived when microammeters became 'micro' enough to be read out through the finder. The Leica CL shared the same metering system. SLR cameras had space to spare and no finder display problems. A problem with nearly all selenium and CdS meters is that their meter values are not really linear. They may be OK for part of the metering range but not for the whole of it. Some advanced types, including the 'outboard' semi-coupled Leicameter types, have two or three micropotentiometers for adjustment, but most hand meters have just one zeroing adjustment – often mechanical, at that. Silicon cells produce a direct current, just like a solar cell, and the very tiny current is amplified by circuitry powered by a battery. This is just a power source, not a reference, so you can design it to use even a common AA battery. This amplification can secure the linearity that ensures correct metering across a very large range. High sensitivity and quick response are other advantages. Silicon cells are over-responsive to red and IR light, so the cell needs a blue filter, hence the "silicon blue cell" we heard of in the late 1960's. I think the Wikipedia entry discusses the difference between reflected and incident metering quite well. This is an important distinction to the practical user. My first meter was a Gossen Sixtar (c. 1959), a selenium meter but with provision for incident metering, and I have preferred that method since then. My present hand meter is a Sixtomat Digital. But the fact is that with an ExpoDisc my M9 can also meter incident light – though a bit less conveniently than with my hand meter. The old man from the Selenium Age 5 Quote Link to post Share on other sites More sharing options...
SJP Posted February 4, 2012 Share #5 Posted February 4, 2012 Look to the history of extinction meters. I have a few but they have all degraded so that they are useless. If you want to go way back, the most novel light meter (however not the best) I've seen is one which is a horizontal strip with drawings of the eye's iris at various constrictions across it with a number below each and a horizontal mirror to look at one's own eyes, and the scene beyond, and below a suggested F-Stop at a given shutter speed based upon the constriction of the viewers pupils. Strange. Really odd. That may be strange & odd, but also remarkably clever. Does it give an EV scale? I guess you can even determine your personal correction factor, presumably all eyes are slightly different. Is the dynamic range of the retina the main problem I wonder? Quote Link to post Share on other sites More sharing options...
pico Posted February 4, 2012 Share #6 Posted February 4, 2012 I like this one. Scroll down to see its size. Quote Link to post Share on other sites More sharing options...
SJP Posted February 4, 2012 Share #7 Posted February 4, 2012 Advertisement (gone after registration) But will it give an accurate incident light reading Nice design, admittedly. Quote Link to post Share on other sites More sharing options...
giordano Posted February 4, 2012 Share #8 Posted February 4, 2012 If you want to go way back, the most novel light meter (however not the best) I've seen is one which is a horizontal strip with drawings of the eye's iris at various constrictions across it with a number below each and a horizontal mirror to look at one's own eyes, and the scene beyond, and below a suggested F-Stop at a given shutter speed based upon the constriction of the viewers pupils. Strange. Really odd. And in low light, you just held your cat up to the mirror. Quote Link to post Share on other sites More sharing options...
giordano Posted February 4, 2012 Share #9 Posted February 4, 2012 Supplementing Lars's excellent potted history: 1) About the same time as selenium-cell exposure meters came into use for reflected and then incident measurement, the first spot-meters were built. To obviate the insensitivity of small selenium cells and galvanometers, they worked by comparing the illumination of the area being measured with that of a standard light source inside the meter. You looked through a little telescope at the scene, and turned the measuring scale until the brightness of the area being measured matched the brightness of the built-in light source. These "spot photometers" were rare and expensive, remained in use even after CdS spotmeters arrived in the 1960s, and are now mostly collectors' pieces. Best known was the SEI. 2) Through-the-lens metering is an obviously good idea (except perhaps for people who prefer incident metering or the Zone system:)) and the first patents seem to have been taken out by Ihagee (Exakta) by 1939 though the technology was lacking. In the event the now almost-forgotten Topcon RE Super was first on the market in 1963, with a CdS cell glued on the back of the mirror, receiving light through narrow gaps in the metallic reflective coating on the front. Alpa (9d) and Pentax (Spotmatic) joined in the following year with CdS cells mounted on the pentaprism. The Alpa used three cells, two aimed at the focusing screen and the third at the eyepiece to compensate for light entering there; a contemporary review said this didn't seem to make any difference. Quote Link to post Share on other sites More sharing options...
gvaliquette Posted February 4, 2012 Share #10 Posted February 4, 2012 Selenium meters were introduced about 1934, the Weston brand being popular in the U.S. Gossen became active in Europe in the late 1930's with their Sixtus brand. Because of the large cell needed to produce current enough for a microammeter, they could be used only for hand meters and in not TTL measuring types built into cameras. Cameras with built-in meters had a cell window in front and a meter needle in a window in the top plate; microammeters of the 1930's to 1950's were too large to be built into finders. The photocell voltage was used directly as input to the ammeter, so no battery was needed. ... The old man from the Selenium Age Thanks, Lars, excellent summary. The part on the selenium meters reminds me of my first SLR: the Contarex "Bull's Eye". Guy Quote Link to post Share on other sites More sharing options...
samiba Posted February 4, 2012 Share #11 Posted February 4, 2012 (edited) One of the best overviews I know on the history of all know light meters you will find here: Belichtungsmesser by Photo but More It is all in german but pictures tell the history very well. Cheers, Michael Edited February 4, 2012 by samiba Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted February 5, 2012 Share #12 Posted February 5, 2012 Thanks, Lars, excellent summary. The part on the selenium meters reminds me of my first SLR: the Contarex "Bull's Eye". Guy The first Nikon Photomic finder (for Nikon F) had a whopping big selenium cell on its front, the second model had CdS metering, and this one metered through the lens. It is a mystery why the Leicaflex had an external CdS cell on the front of its prism as late as in 1964. The old man from the Selenium Age Quote Link to post Share on other sites More sharing options...
giordano Posted February 5, 2012 Share #13 Posted February 5, 2012 The first Nikon Photomic finder (for Nikon F) had a whopping big selenium cell on its front, the second model had CdS metering, and this one metered through the lens. It is a mystery why the Leicaflex had an external CdS cell on the front of its prism as late as in 1964. AFAIK there was never a selenium-cell Photomic head. The selenium meters for Nikon F clipped onto the front of the standard pentaprism finder. IMHO the external CdS cell can be accounted for by slow development and excessive caution in this first SLR : we know the Leicameter MR4 works really well, so let's get Metrawatt to make us something just like to put in the Leicaflex. (FWIW there's a rather unconvincing picture here of a "Leicaflex prototype" with selenium cell.) For me, the mystery is why, in 1964-5 when they would have been producing the initial stocks of R lenses and there were already TTL cameras on the market, they didn't prepare for TTL by installing the second coupling cam from the start. [Note for younger readers: if a SLR has a built-in meter with an external cell, the meter needs to know the f/stop to which the lens is set, and this information is provided by the one cam on the original Leicaflex lenses. With TTL metering, the meter needs to know how many stops the aperture will close by between metering and exposure, and this information is provided by the second cam introduced for the Leicaflex SL. As for the third cam for the R cameras - that was to reduce the cost of developing the R3-R7 bodies from their Minolta originals.] Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted February 5, 2012 Share #14 Posted February 5, 2012 AFAIK there was never a selenium-cell Photomic head. The selenium meters for Nikon F clipped onto the front of the standard pentaprism finder. You may be right there. I never held one – a Nikon F was way out of my economic reach at that time. My first SLR camera was an Edixa Reflex (ouch). The old man from the Selenium Age Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted February 5, 2012 Share #15 Posted February 5, 2012 One of the best overviews I know on the history of all know light meters you will find here:Belichtungsmesser by Photo but More It is all in german but pictures tell the history very well. Cheers, Michael Very good, though he is a bit weak on the technical side. Not lack of knowledge, certainly, but of pedagogical instinct. Still, I saw again, with tears in my eyes, my old Sixtomat 3x ... and my Sixtino, this time without tears. It did really take two hands to operate. The author did miss my Luna-Pro F too. The old man from the Selenium Age 1 Quote Link to post Share on other sites More sharing options...
pico Posted February 5, 2012 Share #16 Posted February 5, 2012 I have a couple Bertram Chrostars and Chronos, because they were so charming, and carried like a pocket watch. None of them work now. Quote Link to post Share on other sites More sharing options...
lars_bergquist Posted February 5, 2012 Share #17 Posted February 5, 2012 Oh, about the Leicameters. The Leicameter MR was not intended for the M4. It was offered from 1963, while the M4 was launched in 1967. The MR had a metering key that protruded from the blunt 'gable end' of the meter housing. This snagged the rewind crank of the M4. Hence the MR-4 model with the sliding button on top. The old man from the Selenium Age Quote Link to post Share on other sites More sharing options...
Michael Geschlecht Posted February 5, 2012 Share #18 Posted February 5, 2012 (edited) Hello Everybody, Nikon had 3 different clip on accessory selenium meters for the F which were called: #1, #2 & #3. These were later replaced by the 1st Photomic head in 1962 - A meter equipped removable pentaprism which, like the original Leicaflex, had it's CdS cell on the outside of the prism. The second Photomic finder in 1965 was the first interchangable finder for a Nikon F which had a BTL CdS meter. I am surprised nobody has mentioned Metrawatt's Metrastar or it's functional twin: Weston's Ranger 9. Ferraris in their day. Like a 1960's Ferrari: Still not bad today. Best Regards, Michael Edited February 5, 2012 by Michael Geschlecht Quote Link to post Share on other sites More sharing options...
sandro Posted February 5, 2012 Author Share #19 Posted February 5, 2012 Just been catching up with my reading here, so thanks a lot to all ofyou providing such interesting information. As a kid I used a selenium meter, Bewi Picolo I think it was called, and I remember the dealer telling me about the differences and much greater accuracy of CdS meters that became available in the nineteensixtees. Interesting are the comparisons that some of you make between various camera branches and producers of handheld meters. Lars I really appreciate your contributions. Thanks (so far), this is very interesting. Lex 1 Quote Link to post Share on other sites More sharing options...
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