Chriscrawfordphoto
Real Men Shoot Film.
I have always been fascinated by light meters and how they work. One thing that has interested me is the color sensitivity of the meters we use for determining exposure in photography. This issue is especially important for reflected light meters, like handheld spotmeters and the built-in meters found in most modern cameras. I decided to test several spotmeters to see what differences, if any, there were in their sensitivity to different colors. The meter that will probably be of most interest is the Zone VI Modified Pentax Digital Spotmeter. This is the only meter I know of whose manufacturer claimed that it had the same color response as film.
Many people assume that the meter simply reads the amount of light, and that the color of the light and the subject does not matter. In fact, the sensors used in exposure meters are not colorblind, nor do they have the same color sensitivity of film, digital camera sensors, or the human eye. When taking a meter reading of a neutral colored object, like a white wall, this isn't an important concern; but we often photograph colored objects, like a red car or green landscape. In that case, color sensitivity matters.
Virtually all meters made since 1980 use a Silicon Photodiode as the light sensor. Silicon Photodiodes have poor sensitivity to blue light, high sensitivity to red light, and very high sensitivity to infrared light. Black and white films have no infrared sensitivity (I'm ignoring specialized IR films, since most photography is done with standard films), and most B&W films have higher sensitivity to blue light than to red. This means the film's color sensitivity is basically the opposite of that of the sensor used in meters! Because of this, meter manufacturers never use a plain Silicon Photodiode. They use what is commonly called a Silicon Blue Cell (SBC). This is a Silicon Photocell with a blue filter over it that reduces the amount of red visible light and infrared light that reaches the cell, and many have additional filtration to further fine-tune the meter's sensitivity to be closer to that of film. Even with that, many are still too sensitive to red and orange and not sensitive enough to blue, and most still have some infrared sensitivity.
The contestants: Pentax Digital Spotmeter, Zone VI Modified Pentax Digital, Gossen Ultra Spot 2, and the Sekonic L-758DR. The Pentax and Gossen meters are dedicated one degree spotmeters, while the Sekonic is an "All in one" meter that does both incident and one degree spotmetering.
The Meters I tested
I did a series of tests with the four handheld spotmeters that I currently own. I tested their sensitivity to different colors of visible light, and to infrared. Before I go to the tests, I'll give a brief description of each of the meters I tested.
Pentax Digital Spotmeter
The Pentax Digital Spotmeter is the earliest and the simplest of the meters I tested. Introduced in 1977, this meter was popularized by Ansel Adams. He used one of these during the last years of his life, and wrote about them in his popular books on photographic technique. Because of Adams, the Pentax Digital has remained extremely popular; especially with photographers who use the Zone System, the exposure metering system that he invented for black and white photography. This has kept the used prices of these meters, which are no longer manufactured, very high.
Despite the name, the meter is not a fully digital meter like more modern meters. The viewfinder gives a digital reading of an exposure value number, with [SUP]1[/SUP]⁄[SUB]3[/SUB] stop accuracy, that you transfer to a mechanical dial on the lens. When set to the correct film speed and the EV number the meter gives you, you can read out all of the aperture/shutter speed combinations that will give correct exposure.
Many users like the simplicity of the design. It has only one button; the one that activates the meter. More modern meters are more complex, with buttons to set film speed, exposure memory, averaging functions, mode selections, etc. Alongside the Digital Spotmeter, Pentax also made the Spotmeter V. Aside from being a lot larger and heavier than the digital meter, the main difference between them is that the Spotmeter V uses a moving needle to point to the EV numbers in the viewfinder instead of a digital readout. I used to have a Spotmeter V and it was a fine meter aside from the size and weight. Do not buy the earlier Pentax Spotmeters (the 1/21 Spotmeter, the Spotmeter II, and Spotmeter III); they require mercury batteries that are no longer made.
Zone VI Modified Pentax Digital Spotmeter
Zone VI Studios was a manufacturer and retailer of large format cameras, darkroom equipment, and photo accessories. In the early 1980s, the company's founder, Fred Picker, began to think about the issues of spotmeter color sensitivity. He hired Paul Horowitz, a Harvard professor, physicist, and electrical engineer to design a set of filters to modify the color sensitivity of a meter to match that of film. Horowitz and Richard Ritter, a photographer and technician who worked for Zone VI, devised a way to modify the Pentax Digital Spotmeter, the Pentax Spotmeter V, and the Soligor spotmeters.
According to the Zone VI Studios catalogue, this involved replacing the SBC metering cell that Pentax used with a different one, then adding filters to block infrared and ultraviolet light, and filters to modify the meter's visible light color sensitivity to match that of film. It was also claimed that the modified meters had additional light baffles and a new light-absorbing coating inside to reduce flare in the meter's optical system.
Zone VI sold modified meters, and also modified meters that customers sent in. Richard Ritter was the man who actually did the modifications, and after Zone VI closed he continued offering repair and calibration services for the Pentax meters, both modified and unmodified. He is the only one I know of still repairing these old meters. I had him calibrate mine before I did these tests.
The Zone VI modifications have been controversial. They added a couple hundred dollars to the price of the meter when bought new, and today they continue to command a hefty premium over standard, unmodified Pentax spotmeters. For years, people on internet photo forums have debated whether the modifications actually made a difference in the meters' accuracy. Some users believed that the modifications made a huge difference in accuracy, and others thought there were no real differences. Several years ago, Paul Butzi, a photographer and former writer for the now-defunct Photo Techniques Magazine, did a series of tests comparing the standard factory version of the Pentax Digital Spotmeter with the Zone VI modified version. His results differed from mine somewhat, but unfortunately his website has been down for a few years, so I can't link to his results.
Many people believe that the Zone VI modifications were designed to make the meter match the color sensitivity of Kodak Tri-X, which was Fred Picker's favorite film. Richard Ritter has stated that the modifications were not specifically for Tri-X, but were for an average of several films made back when the modifications were devised.
The Zone VI versions of the Pentax meters operate exactly the same as the factory original versions. The differences are all internal.
Gossen Ultra Spot 2
The Gossen Ultra Spot 2 was my first spotmeter. I bought it when I was a 20 year old art student and used it for many years. I noticed early on that it was too sensitive to red, more so than other meters. This was especially apparent when using warm light sources like incandescent light and halogen lights; it read about one stop too high under those lights (meaning the readings produced one stop of underexposure)!
These meters were very expensive when new, and are uncommon on the used market. Most I have seen are no longer accurate, and no one seems willing to work on them to recalibrate them. I have two of them, the accurate one I used for this test and one that is no longer linear (it gives accurate readings in bright light and reads [SUP]1[/SUP]⁄[SUB]2[/SUB] stop too high in dim light). I have called nearly every camera repair tech in the USA and NO ONE will touch it. I would not buy one of these now. It is unfortunate, because the Ultra Spot 2 has the best viewfinder of any of the meters I have used (more on that later).
Sekonic L-758DR
For many years now, Sekonic has made a series of "All in one" combo meters that have both a built-in spotmeter and an incident light meter. In my opinion, the L-758DR is the best of them, though it was replaced by the L-858 a few years ago. The newer meter uses a touchscreen, which I strongly dislike. The L-758DR is great if you need an incident meter and a spotmeter and don't want to buy two meters. I use it for all of my digital work, since I normally use an incident meter for that (and the spotmeter comes in handy for times an incident meter won't work, like photographing lighted signs). I only tested the spotmeter for this article.
Sekonic isn't the only company to make combo meters like this, though they were the pioneers of the concept. I had the original one, the L-508, for many years. Was a good, accurate meter; but the spotmeter did not read out in the viewfinder like the L-758DR does, and did not work as well in low light. If you get a Sekonic combo meter, I recommend the L758DR or its predecessor, the L-558. Minolta (Flash Meter VI), Gossen (Starlite and Starlite 2), and Kenko (KFM-2100 and KFM-2200) have also made combo meters. I think the Sekonics are the best of them.
Many people assume that the meter simply reads the amount of light, and that the color of the light and the subject does not matter. In fact, the sensors used in exposure meters are not colorblind, nor do they have the same color sensitivity of film, digital camera sensors, or the human eye. When taking a meter reading of a neutral colored object, like a white wall, this isn't an important concern; but we often photograph colored objects, like a red car or green landscape. In that case, color sensitivity matters.
Virtually all meters made since 1980 use a Silicon Photodiode as the light sensor. Silicon Photodiodes have poor sensitivity to blue light, high sensitivity to red light, and very high sensitivity to infrared light. Black and white films have no infrared sensitivity (I'm ignoring specialized IR films, since most photography is done with standard films), and most B&W films have higher sensitivity to blue light than to red. This means the film's color sensitivity is basically the opposite of that of the sensor used in meters! Because of this, meter manufacturers never use a plain Silicon Photodiode. They use what is commonly called a Silicon Blue Cell (SBC). This is a Silicon Photocell with a blue filter over it that reduces the amount of red visible light and infrared light that reaches the cell, and many have additional filtration to further fine-tune the meter's sensitivity to be closer to that of film. Even with that, many are still too sensitive to red and orange and not sensitive enough to blue, and most still have some infrared sensitivity.
The contestants: Pentax Digital Spotmeter, Zone VI Modified Pentax Digital, Gossen Ultra Spot 2, and the Sekonic L-758DR. The Pentax and Gossen meters are dedicated one degree spotmeters, while the Sekonic is an "All in one" meter that does both incident and one degree spotmetering.
The Meters I tested
I did a series of tests with the four handheld spotmeters that I currently own. I tested their sensitivity to different colors of visible light, and to infrared. Before I go to the tests, I'll give a brief description of each of the meters I tested.
Pentax Digital Spotmeter
The Pentax Digital Spotmeter is the earliest and the simplest of the meters I tested. Introduced in 1977, this meter was popularized by Ansel Adams. He used one of these during the last years of his life, and wrote about them in his popular books on photographic technique. Because of Adams, the Pentax Digital has remained extremely popular; especially with photographers who use the Zone System, the exposure metering system that he invented for black and white photography. This has kept the used prices of these meters, which are no longer manufactured, very high.
Despite the name, the meter is not a fully digital meter like more modern meters. The viewfinder gives a digital reading of an exposure value number, with [SUP]1[/SUP]⁄[SUB]3[/SUB] stop accuracy, that you transfer to a mechanical dial on the lens. When set to the correct film speed and the EV number the meter gives you, you can read out all of the aperture/shutter speed combinations that will give correct exposure.
Many users like the simplicity of the design. It has only one button; the one that activates the meter. More modern meters are more complex, with buttons to set film speed, exposure memory, averaging functions, mode selections, etc. Alongside the Digital Spotmeter, Pentax also made the Spotmeter V. Aside from being a lot larger and heavier than the digital meter, the main difference between them is that the Spotmeter V uses a moving needle to point to the EV numbers in the viewfinder instead of a digital readout. I used to have a Spotmeter V and it was a fine meter aside from the size and weight. Do not buy the earlier Pentax Spotmeters (the 1/21 Spotmeter, the Spotmeter II, and Spotmeter III); they require mercury batteries that are no longer made.
Zone VI Modified Pentax Digital Spotmeter
Zone VI Studios was a manufacturer and retailer of large format cameras, darkroom equipment, and photo accessories. In the early 1980s, the company's founder, Fred Picker, began to think about the issues of spotmeter color sensitivity. He hired Paul Horowitz, a Harvard professor, physicist, and electrical engineer to design a set of filters to modify the color sensitivity of a meter to match that of film. Horowitz and Richard Ritter, a photographer and technician who worked for Zone VI, devised a way to modify the Pentax Digital Spotmeter, the Pentax Spotmeter V, and the Soligor spotmeters.
According to the Zone VI Studios catalogue, this involved replacing the SBC metering cell that Pentax used with a different one, then adding filters to block infrared and ultraviolet light, and filters to modify the meter's visible light color sensitivity to match that of film. It was also claimed that the modified meters had additional light baffles and a new light-absorbing coating inside to reduce flare in the meter's optical system.
Zone VI sold modified meters, and also modified meters that customers sent in. Richard Ritter was the man who actually did the modifications, and after Zone VI closed he continued offering repair and calibration services for the Pentax meters, both modified and unmodified. He is the only one I know of still repairing these old meters. I had him calibrate mine before I did these tests.
The Zone VI modifications have been controversial. They added a couple hundred dollars to the price of the meter when bought new, and today they continue to command a hefty premium over standard, unmodified Pentax spotmeters. For years, people on internet photo forums have debated whether the modifications actually made a difference in the meters' accuracy. Some users believed that the modifications made a huge difference in accuracy, and others thought there were no real differences. Several years ago, Paul Butzi, a photographer and former writer for the now-defunct Photo Techniques Magazine, did a series of tests comparing the standard factory version of the Pentax Digital Spotmeter with the Zone VI modified version. His results differed from mine somewhat, but unfortunately his website has been down for a few years, so I can't link to his results.
Many people believe that the Zone VI modifications were designed to make the meter match the color sensitivity of Kodak Tri-X, which was Fred Picker's favorite film. Richard Ritter has stated that the modifications were not specifically for Tri-X, but were for an average of several films made back when the modifications were devised.
The Zone VI versions of the Pentax meters operate exactly the same as the factory original versions. The differences are all internal.
Gossen Ultra Spot 2
The Gossen Ultra Spot 2 was my first spotmeter. I bought it when I was a 20 year old art student and used it for many years. I noticed early on that it was too sensitive to red, more so than other meters. This was especially apparent when using warm light sources like incandescent light and halogen lights; it read about one stop too high under those lights (meaning the readings produced one stop of underexposure)!
These meters were very expensive when new, and are uncommon on the used market. Most I have seen are no longer accurate, and no one seems willing to work on them to recalibrate them. I have two of them, the accurate one I used for this test and one that is no longer linear (it gives accurate readings in bright light and reads [SUP]1[/SUP]⁄[SUB]2[/SUB] stop too high in dim light). I have called nearly every camera repair tech in the USA and NO ONE will touch it. I would not buy one of these now. It is unfortunate, because the Ultra Spot 2 has the best viewfinder of any of the meters I have used (more on that later).
Sekonic L-758DR
For many years now, Sekonic has made a series of "All in one" combo meters that have both a built-in spotmeter and an incident light meter. In my opinion, the L-758DR is the best of them, though it was replaced by the L-858 a few years ago. The newer meter uses a touchscreen, which I strongly dislike. The L-758DR is great if you need an incident meter and a spotmeter and don't want to buy two meters. I use it for all of my digital work, since I normally use an incident meter for that (and the spotmeter comes in handy for times an incident meter won't work, like photographing lighted signs). I only tested the spotmeter for this article.
Sekonic isn't the only company to make combo meters like this, though they were the pioneers of the concept. I had the original one, the L-508, for many years. Was a good, accurate meter; but the spotmeter did not read out in the viewfinder like the L-758DR does, and did not work as well in low light. If you get a Sekonic combo meter, I recommend the L758DR or its predecessor, the L-558. Minolta (Flash Meter VI), Gossen (Starlite and Starlite 2), and Kenko (KFM-2100 and KFM-2200) have also made combo meters. I think the Sekonics are the best of them.
