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.
Chriscrawfordphoto
Real Men Shoot Film.
The Color Sensitivity Test
To test the meters' responses to different colors in the visible spectrum, I took readings from an Xrite Colorchecker Classic. Because the light outdoors in Indiana can be inconsistent in brightness over time (and I had to do nearly 200 meter readings for this, which takes a long time), I used daylight balanced studio lights. I lit the Colorchecker with two Cool-Lux 5600K LED studio lights. These are professional level lights with a CRI rating of 95; I have used them for a lot of commercial photography work, and the color rendering is accurate.
Each meter reading was done twice to be sure of accuracy. Before doing the test, I used an incident meter (the Sekonic L-758DR in incident mode with the dome in the 'down' position so that it acts like a flat diffuser) to check the evenness of illumination at several points on the Colorchecker. It was flawlessly even; not even a [SUP]1[/SUP]⁄[SUB]10[/SUB] stop variance.
The chart above shows the readings (EV at ISO 100) on each color square from the four meters. The "Value" number is from the information sheet that came with the Colorchecker. Xrite assigns a value to each color that indicates the grayscale brightness of each. Zero is pure black, and ten is pure white. None of the squares, not even the white one or the black one, reach the extremes of the scale.
The Xrite Value number is important because a meter whose color sensitivity matches that of the human eye should give identical readings from any two colors that have the same grayscale value. None of the meters were perfect in that regard. Of course, the question is: does it matter? B&W film definitely does NOT have the same color sensitivity as the human eye, so for B&W film photography a meter that matched human visual response would actually be less accurate! What about color film, or digital photography? Since a film or sensor that deviated far from the color response of human vision would likely produce poor color rendering, I would expect that a meter that is closer to human visual response would be better for color film and digital work.
The Results of the Color Sensitivity Test
If you look at the numbers on the chart, you'll see that there really isn't a whole lot of difference between the meters when reading different colors under daylight-balanced lights. On many of the colors, all of the meters read the same, or very nearly so. On most of the colors, the four meters are all within [SUP]1[/SUP]⁄[SUB]3[/SUB] of a stop. There are some things that stand out when evaluating the numbers:
• The Zone VI Modified Pentax meter consistently reads higher on blue squares and lower on the red squares than the other meters. This would make it more accurate for most B&W films.
• The Gossen Ultra Spot 2 consistently reads lower on blue squares and higher on red squares than the other meters. This makes it the least suitable meter for either B&W or color photography!
• The Sekonic L-758DR and the standard, unmodified Pentax Digital Spotmeter agree with each other pretty closely and comparing their readings of groups of colors with the same grayscale values, they're fairly close to having color sensitivity that matches the human eye. These are probably the better choice for color photography. These meters might also be better for modern B&W films like Tmax 400, which have a more even color sensitivity than older films like Tri-X.
To test the meters' responses to different colors in the visible spectrum, I took readings from an Xrite Colorchecker Classic. Because the light outdoors in Indiana can be inconsistent in brightness over time (and I had to do nearly 200 meter readings for this, which takes a long time), I used daylight balanced studio lights. I lit the Colorchecker with two Cool-Lux 5600K LED studio lights. These are professional level lights with a CRI rating of 95; I have used them for a lot of commercial photography work, and the color rendering is accurate.
Each meter reading was done twice to be sure of accuracy. Before doing the test, I used an incident meter (the Sekonic L-758DR in incident mode with the dome in the 'down' position so that it acts like a flat diffuser) to check the evenness of illumination at several points on the Colorchecker. It was flawlessly even; not even a [SUP]1[/SUP]⁄[SUB]10[/SUB] stop variance.
The chart above shows the readings (EV at ISO 100) on each color square from the four meters. The "Value" number is from the information sheet that came with the Colorchecker. Xrite assigns a value to each color that indicates the grayscale brightness of each. Zero is pure black, and ten is pure white. None of the squares, not even the white one or the black one, reach the extremes of the scale.
The Xrite Value number is important because a meter whose color sensitivity matches that of the human eye should give identical readings from any two colors that have the same grayscale value. None of the meters were perfect in that regard. Of course, the question is: does it matter? B&W film definitely does NOT have the same color sensitivity as the human eye, so for B&W film photography a meter that matched human visual response would actually be less accurate! What about color film, or digital photography? Since a film or sensor that deviated far from the color response of human vision would likely produce poor color rendering, I would expect that a meter that is closer to human visual response would be better for color film and digital work.
The Results of the Color Sensitivity Test
If you look at the numbers on the chart, you'll see that there really isn't a whole lot of difference between the meters when reading different colors under daylight-balanced lights. On many of the colors, all of the meters read the same, or very nearly so. On most of the colors, the four meters are all within [SUP]1[/SUP]⁄[SUB]3[/SUB] of a stop. There are some things that stand out when evaluating the numbers:
• The Zone VI Modified Pentax meter consistently reads higher on blue squares and lower on the red squares than the other meters. This would make it more accurate for most B&W films.
• The Gossen Ultra Spot 2 consistently reads lower on blue squares and higher on red squares than the other meters. This makes it the least suitable meter for either B&W or color photography!
• The Sekonic L-758DR and the standard, unmodified Pentax Digital Spotmeter agree with each other pretty closely and comparing their readings of groups of colors with the same grayscale values, they're fairly close to having color sensitivity that matches the human eye. These are probably the better choice for color photography. These meters might also be better for modern B&W films like Tmax 400, which have a more even color sensitivity than older films like Tri-X.
Chriscrawfordphoto
Real Men Shoot Film.
Infrared Sensitivity
As I noted in the introduction, Silicon Photodiodes are highly sensitive to Infrared. This is important because normal B&W and color films are not sensitive to IR radiation, and the human eye cannot see it. Digital camera sensors are, but camera manufacturers cover them with a filter that completely blocks IR.
Because film and digital sensors are not sensitive to IR, a meter that is sensitive to it will think there is more light than there really is when metering in situations where there is a lot of infrared. This would produce an underexposed photograph. Meter manufacturers use Silicon Blue Cells, Silicon Photodiodes with a blue filter over them that blocks some of the IR radiation and reduces the meter's red sensitivity in the visible light range. Despite this, most meters do still have some IR sensitivity.
When Does IR Sensitivity Matter?
Some types of light produce a lot of infrared radiation. Incandescent light bulbs and halogen bulbs are both very high in infrared. This is because they produce light by passing electricity through a thin metal wire, which causes it to become hot enough to produce both heat and visible light. They're not very efficient; most of the electrical energy is transformed into heat and IR radiation, not visible light. This is why these types of light bulbs are being replaced now with LED bulbs; LEDs produce more light and less heat from the electricity that powers them.
If you photograph under incandescent or halogen lights, your photographs will be underexposed if you use a light meter that is too sensitive to infrared.
When photographing under daylight, some types of subject matter reflect large amounts of infrared radiation; sometimes more than the amount of visible light. This is a concern for landscape photographers, as green foliage is probably the most extreme example of this phenomenon. Photographed in black and white, the leaves of plants and trees will usually render a middle gray or dark gray. If you photographed them with Infrared Film, those same leaves would be a bright white due to the high IR reflectance of foliage! Spotmeters that are sensitive to Infrared can cause underexposure if you base exposure off of readings of grass or tree leaves.
One of the main benefits claimed for the Zone VI Modified spotmeters was the elimination of the meter's infrared sensitivity, which would make them more accurate for landscape photography.
Testing for IR Sensitivity
To test the meters for infrared sensitivity, I obtained a B+W 486 filter. This filter completely blocks both infrared and ultraviolet radiation, so that the meter will only see light in the visible spectrum. I then took readings of a white card lit by incandescent light bulbs, with and without the filter mounted on the lens of each meter. Incandescent bulbs produce extremely high amounts of IR radiation, making them ideal for this test.
Infrared Test Results
The table above shows the results of the IR Sensitivity Test. The numbers are EV readings at ISO 100.
• Only the Zone VI Modified Pentax Digital Spotmeter showed no difference between the readings done with and without the IR-blocking filter.
• Interestingly, all of the other meters read essentially the same as each other with the filter, though without the filter they gave quite different readings.
• The Zone VI Modified meter read 1/3 stop lower than the others did when they were filtered. I think this is because the visible light from incandescent bulbs is quite red, and the Zone VI meter is less red-sensitive than the other meters.
• The unmodified Pentax Meter read exactly one stop higher than the Zone VI Modified meter without the IR-blocking filter, although they agreed with each other exactly when reading the white square on the Colorchecker under daylight-balanced lights.
• The Gossen Ultra Spot 2 performed even worse, with the highest IR sensitivity of any of the meters I tested.
Flare
Spotmeters use a fairly complex optical system that includes a lens and a semi-transparent mirror that allows some light to pass through to the meter cell and reflects the rest to the viewfinder system. Flare in the meter's optics can cause inaccurate readings. The most obvious source of flare would be a light source visible in the viewfinder; but even when metering objects that have no lights nearby, you can have flare. If you meter a dark object that is next to a light toned object or surrounded by a light toned background, flare can throw off your readings.
The effect of flare is to cause the meter to read too high; meaning that it will think the dark toned object is lighter than it really is. This causes underexposure.
I am working on a test procedure to give more exacting data on the amount of flare from the meters I've tested. Until then, I will say that my experience has been that dedicated spotmeters like the Pentax spotmeters and the Gossen Ultra Spot 2 have less flare than incident/spot combo meters like the Sekonics and the Minolta Flash Meter VI. It is unfortunate that no one today still manufactures a true dedicated one degree spotmeter.
Conclusion
The Sekonic L-758DR, the Pentax Digital Spotmeter, and the Zone VI Modified Pentax Meter are all fine meters, and any of them would be a good choice. That said, here are my recommendations:
• For B&W photography with most films, the Zone VI Modified meter's color sensitivity and lack of infrared sensitivity make it a slightly better choice if you can find one at a good price.
• The B+W 486 filter blocks infrared without affecting meter readings in situations where IR is not present in high amounts. This gives you the most important part of the modifications that Zone VI Studios did to the Pentax spotmeters that they modified and sold. The filter costs about $50 and works on any spotmeter. I now have one on my unmodified Pentax Digital Spotmeter and my Sekonic L-758DR.
• For color photography, or for modern B&W films that have more even color sensitivity (like Kodak Tmax 400), the regular factory-standard unmodified Pentax Digital Spotmeter and the Sekonic L-758DR are probably more accurate than the Zone VI Modified meter.
• I do not recommend the Gossen Ultra Spot 2 because its color sensitivity is not well matched to film, its IR sensitivity is very high, and they cannot be repaired or recalibrated anymore. In the months before I wrote this article, I handled a number of these meters and every one was out of calibration. I was fortunate to have a good one in my collection to use for this experiment. I have noticed that the color and IR sensitivity issues I noted with this meter seem common on Gossen meters generally. I have owned several of Gossen's normal non-spot-meters like the Ultra Pro and the Luna Pro Digital and all had the same very high sensitivity to red and to infrared.
• It is a shame that no one makes a dedicated spotmeter anymore. Sekonic, Gossen, and Kenko make incident/spot combos that have a one degree spotmeter; but their higher flare makes them inferior to meters that only do spotmetering. They are convenient though. I love my Sekonic, but I do have to remember its propensity to flare when reading dark tones surrounded by lighter tones. I mostly use it for my digital work, which is mostly done with the incident meter.
As I noted in the introduction, Silicon Photodiodes are highly sensitive to Infrared. This is important because normal B&W and color films are not sensitive to IR radiation, and the human eye cannot see it. Digital camera sensors are, but camera manufacturers cover them with a filter that completely blocks IR.
Because film and digital sensors are not sensitive to IR, a meter that is sensitive to it will think there is more light than there really is when metering in situations where there is a lot of infrared. This would produce an underexposed photograph. Meter manufacturers use Silicon Blue Cells, Silicon Photodiodes with a blue filter over them that blocks some of the IR radiation and reduces the meter's red sensitivity in the visible light range. Despite this, most meters do still have some IR sensitivity.
When Does IR Sensitivity Matter?
Some types of light produce a lot of infrared radiation. Incandescent light bulbs and halogen bulbs are both very high in infrared. This is because they produce light by passing electricity through a thin metal wire, which causes it to become hot enough to produce both heat and visible light. They're not very efficient; most of the electrical energy is transformed into heat and IR radiation, not visible light. This is why these types of light bulbs are being replaced now with LED bulbs; LEDs produce more light and less heat from the electricity that powers them.
If you photograph under incandescent or halogen lights, your photographs will be underexposed if you use a light meter that is too sensitive to infrared.
When photographing under daylight, some types of subject matter reflect large amounts of infrared radiation; sometimes more than the amount of visible light. This is a concern for landscape photographers, as green foliage is probably the most extreme example of this phenomenon. Photographed in black and white, the leaves of plants and trees will usually render a middle gray or dark gray. If you photographed them with Infrared Film, those same leaves would be a bright white due to the high IR reflectance of foliage! Spotmeters that are sensitive to Infrared can cause underexposure if you base exposure off of readings of grass or tree leaves.
One of the main benefits claimed for the Zone VI Modified spotmeters was the elimination of the meter's infrared sensitivity, which would make them more accurate for landscape photography.
Testing for IR Sensitivity
To test the meters for infrared sensitivity, I obtained a B+W 486 filter. This filter completely blocks both infrared and ultraviolet radiation, so that the meter will only see light in the visible spectrum. I then took readings of a white card lit by incandescent light bulbs, with and without the filter mounted on the lens of each meter. Incandescent bulbs produce extremely high amounts of IR radiation, making them ideal for this test.
Infrared Test Results
| Without Filter | With IR-Blocking Filter | Difference | |
| Sekonic L-758DR | 6.1 | 5.7 | 0.4 |
| Pentax Digital Spotmeter | 6.3 | 5.7 | 0.6 |
| Zone VI Modified Pentax | 5.3 | 5.3 | 0 |
| Gossen Ultra Spot 2 | 6.9 | 5.8 | 1.1 |
The table above shows the results of the IR Sensitivity Test. The numbers are EV readings at ISO 100.
• Only the Zone VI Modified Pentax Digital Spotmeter showed no difference between the readings done with and without the IR-blocking filter.
• Interestingly, all of the other meters read essentially the same as each other with the filter, though without the filter they gave quite different readings.
• The Zone VI Modified meter read 1/3 stop lower than the others did when they were filtered. I think this is because the visible light from incandescent bulbs is quite red, and the Zone VI meter is less red-sensitive than the other meters.
• The unmodified Pentax Meter read exactly one stop higher than the Zone VI Modified meter without the IR-blocking filter, although they agreed with each other exactly when reading the white square on the Colorchecker under daylight-balanced lights.
• The Gossen Ultra Spot 2 performed even worse, with the highest IR sensitivity of any of the meters I tested.
Flare
Spotmeters use a fairly complex optical system that includes a lens and a semi-transparent mirror that allows some light to pass through to the meter cell and reflects the rest to the viewfinder system. Flare in the meter's optics can cause inaccurate readings. The most obvious source of flare would be a light source visible in the viewfinder; but even when metering objects that have no lights nearby, you can have flare. If you meter a dark object that is next to a light toned object or surrounded by a light toned background, flare can throw off your readings.
The effect of flare is to cause the meter to read too high; meaning that it will think the dark toned object is lighter than it really is. This causes underexposure.
I am working on a test procedure to give more exacting data on the amount of flare from the meters I've tested. Until then, I will say that my experience has been that dedicated spotmeters like the Pentax spotmeters and the Gossen Ultra Spot 2 have less flare than incident/spot combo meters like the Sekonics and the Minolta Flash Meter VI. It is unfortunate that no one today still manufactures a true dedicated one degree spotmeter.
Conclusion
The Sekonic L-758DR, the Pentax Digital Spotmeter, and the Zone VI Modified Pentax Meter are all fine meters, and any of them would be a good choice. That said, here are my recommendations:
• For B&W photography with most films, the Zone VI Modified meter's color sensitivity and lack of infrared sensitivity make it a slightly better choice if you can find one at a good price.
• The B+W 486 filter blocks infrared without affecting meter readings in situations where IR is not present in high amounts. This gives you the most important part of the modifications that Zone VI Studios did to the Pentax spotmeters that they modified and sold. The filter costs about $50 and works on any spotmeter. I now have one on my unmodified Pentax Digital Spotmeter and my Sekonic L-758DR.
• For color photography, or for modern B&W films that have more even color sensitivity (like Kodak Tmax 400), the regular factory-standard unmodified Pentax Digital Spotmeter and the Sekonic L-758DR are probably more accurate than the Zone VI Modified meter.
• I do not recommend the Gossen Ultra Spot 2 because its color sensitivity is not well matched to film, its IR sensitivity is very high, and they cannot be repaired or recalibrated anymore. In the months before I wrote this article, I handled a number of these meters and every one was out of calibration. I was fortunate to have a good one in my collection to use for this experiment. I have noticed that the color and IR sensitivity issues I noted with this meter seem common on Gossen meters generally. I have owned several of Gossen's normal non-spot-meters like the Ultra Pro and the Luna Pro Digital and all had the same very high sensitivity to red and to infrared.
• It is a shame that no one makes a dedicated spotmeter anymore. Sekonic, Gossen, and Kenko make incident/spot combos that have a one degree spotmeter; but their higher flare makes them inferior to meters that only do spotmetering. They are convenient though. I love my Sekonic, but I do have to remember its propensity to flare when reading dark tones surrounded by lighter tones. I mostly use it for my digital work, which is mostly done with the incident meter.
CMur12
Well-known
That was a lot of work, Chris. Thanks!
I was surprised to see that combination spot/incident meters have more flare. I have a Minolta Spotmeter F and a couple of Minolta incident light meters, so it sounds like I'm well served sticking with separate meters.
Since I mainly shoot color, these meters should be fine, but it's good to know about the availability of an IR filter for B&W metering.
- Murray
I was surprised to see that combination spot/incident meters have more flare. I have a Minolta Spotmeter F and a couple of Minolta incident light meters, so it sounds like I'm well served sticking with separate meters.
Since I mainly shoot color, these meters should be fine, but it's good to know about the availability of an IR filter for B&W metering.
- Murray
Chriscrawfordphoto
Real Men Shoot Film.
I think the infrared sensitivity is an issue for color work too. I did a quick experiment. These three photos were shot with a digital SLR using the same incandescent lights I used for the IR sensitivity tests of the meters. I metered off the Kodak 18% gray card, using the exposure setting from that.
Sekonic L-758DR, no filter
Sekonic L-758DR with the B+W 486 IR-Block filter
Zone VI Modified Pentax Digital Spotmeter
In my opinion, the unfiltered Sekonic meter gave an underexposed image. The Sekonic with the IR-Block filter gave a good rendering, maybe just slightly too dark. The Zone VI Modified Meter overexposed slightly, I think.
Thankyou for this- very interesting.
These findings also apply to meters built into cameras: I found that the Meter Cell of the M9 has a 5% leakage in the IR, but the CCD does not. The type of cover glass on most meter cells is like the cover of the M8. The sensor stack of most cameras lets in much less IR than that of the meter.
These findings also apply to meters built into cameras: I found that the Meter Cell of the M9 has a 5% leakage in the IR, but the CCD does not. The type of cover glass on most meter cells is like the cover of the M8. The sensor stack of most cameras lets in much less IR than that of the meter.
Hari
Well-known
My spotmeter is the Minolta Spotmeter F. It spotmeters for flash as well.
Chriscrawfordphoto
Real Men Shoot Film.
I remember the debacle with the M8 sensor's weak IR filtering. Leica was giving M8 buyers free IR-cut filters. The filters were 'interference filters' just like the B+W 486 I used for my meter tests. Interference filters don't absorb IR; they reflect it away from the filter. Apparently that allows a more complete blocking of IR with a more precise cutoff for the wavelengths of light the filter blocks.
Chriscrawfordphoto
Real Men Shoot Film.
Lots of spotmeters can meter flash. The Gossen Ultra Spot 2 and Sekonic L-758DR both do flash. Other flash-capable spotmeters include the Gossen Starlite, Sekonic L-778, Minolta Flash Meter VI, and Kenko KFM-2200. In addition, all of Sekonic's other incident/spot combo meters can meter flash with both the incident and spot meters.
Cascadilla
Well-known
Thanks for this testing and information--I've always thought that the combination spot/incident meters were needlessly complex and a recipe for mistakes when doing commercial work under pressure. My main flash meter has been a Sekonic L 718 since the late 1990's and I've had a Soligor 1 degree spot meter for almost 40 years. At one point I dropped it and sent it off to Zone VI to be recalibrated and modified. I didn't notice a huge change for zone system work when I got it back but it was a bit more consistent than before. All I've done since then is to replace 9 volt batteries once in a while. My only gripe is size and weight, since it is comparable to the Pentax Spotmeter V, but it has worked well for me as a meter.