How do you use an incident light meter?

Ariston · Oct 21, 2019

I recently picked up an incident light meter and went for a hike in the woods to give it a try. I thought it might provide a short-cut for when I was not in the mood for spot metering. I tested it at home with a digital camera several times before using it for film.

Well, when I developed my roll, the shots I had taken in the woods with the incident meter were mostly underexposed. According to Gossen, I am supposed to point the incident meter from the subject to the camera to record the light falling on the subject from the camera's position. I am wondering if I neglected to pay attention, and maybe some rays of sunlight were shooting through the canopy and hitting the dome of my meter.

Should I instead have simply shaded the dome and taken a reading? What do you guys do? I thought this would provide a simpler solution for times when I wanted things to be simpler...

c41 · Oct 21, 2019

You're metering from your subject with an incident meter. What was your subject? The shaded areas?
In which case, yes, just stick the meter in full shade and take a reading.
This article is maybe useful to get your head in the right space.
https://petapixel.com/2016/07/30/old-school-meter-expose-lighting-situation/

Life should definitely be simpler with an incident meter if you are able to put it in the same light as your subject. Stick with it and you'll be happy in no time.

Mainecoonmaniac · Oct 21, 2019

An incident light meter measures light falling on your subject. One thing you could do is to use a manual digital camera to learn how to use your meter. Take a measurement, enter the setting into your camera and see if you're getting the results you think you're going to get. Youtube has great videos on using a light meter.

grimp0teuthis · Oct 21, 2019

An incident meter doesn't give you camera settings for "the correct exposure", it gives you camera settings for placing the light you measured at middle gray. If you meter in bright sunlight, the settings it gives you will consider that sunlight to be middle gray (and your shadows and midtones will be darker/underexposed) and if you meter in a dark shadow, it will consider the shadow to be middle gray (and your shadows will be brighter).

On black and white or color negative film, you want to "meter for the shadows", so take your reading from a relatively shady (but not extremely dark) part of the scene. This is because negative film is good at keeping detail in the highlights when there is a lot of light, but not good at keeping detail in the shadows when there isn't enough light. Slide film and digital cameras are not as good at holding detail in highlights when there is a lot of light.

Try metering in a shady part of the scene. Think about whether you want that shady part to be middle gray, lighter, or darker, and how that will affect the other parts of the scene, then put in your camera settings.

Dan Daniel · Oct 21, 2019

Listen to c41. Keep practicing, read a few articles. It will make sense eventually. And once it sinks in, you will be happy.

Realize that it is a very very different way of metering than spot metering. Put simply, and yes somewhat simplistically, a reflected light meter (a spot meter is this) is telling you about the object being photographed. Incident metering is telling you about the light falling on the scene. Big difference in how you think about things. Going from reflected to incident isn't like going from farenheit to celsius. It's like going from skateboard to hang glider. You may be traveling the same territory but you have to think about it very differently.

There are reasons cinema lighting directors and camera people use incident meters. Setting scenes and running film can cost thousands of dollars. Little room for mistakes. Give it some time, have some faith. Tree shadow are actually one of the hardest thing to incident meter in many ways so you started at the deep end.

Paul Howell · Oct 21, 2019

When I use an incident meter with roll I meter for the shadows and use VC filters when printing to get the right highlights. If you meter for the highlight you should get printable highlights but your shadows will be underexposed. which is why AA used a spot meter. Phil David developed BTZS using a incident mete, he metered for the shadows to set exposure then metered for the high light to determine development times.

ic-racer · Oct 21, 2019

Ariston said:
Well, when I developed my roll, the shots I had taken in the woods with the incident meter were mostly underexposed. .

Increase the Exposure Index by one stop and try again. Incident metering a subject other than a face or copy work is a skill to master as is spot metering.

Mr Bill · Oct 21, 2019

I would say that an incident meter is exceptionally useful when the subject is (mostly) frontally lit. I would use them almost exclusively for studio portrait type work, in which I would make sure to shield the meter from either a hair light or "kicker" (from behind). This would be with a "dome" on the meter. If you were doing flat artwork you would prefer to use a flat diffuser which is sensitive to the same angular fall-off as the painting, etc., and which would not be able to "see" lights from behind the artwork.

When you are in places that are NOT frontally lit then your judgment comes into play.

For tricky outdoor scenes (ie not frontally lit) I would prefer a reflective meter. If I HAD to use an incident meter for this... I'd probably take readings in the most shaded area, making "estimates" (wild guesses) as to what it takes to get a little shadow detail. Then perhaps a reading in the lighter areas to see if I can find a happy medium, or whatever. It might be worthwhile to spend a couple hours with both meters - your incident AND spot - seeing if you can correlate your incident readings to the spot readings (which I would take to be more "correct").

People who live by their incident meters have worked out (according to literature) methods of metering just about anything, but I don't really trust 'em IF THE SUBJECT IS NOT FRONTALLY LIT.

Bill Burk · Oct 21, 2019

OK if you were in deep forest and a shaft of sunlight hit your white dome, then you gave the deep forest the exposure that would have been right for bright sun.

Otherwise, I think it may help to see pictures and a little story about where you held your meter.

'Generally' if you aim the meter at your camera from subject position, and the light hitting the meter is the same light that's hitting your subject, your subject should be properly exposed if you got the other stuff right (ASA setting, f/stop and shutter setting, you read the meter correctly etcetera...)

Chan Tran · Oct 21, 2019

Incident light meter requires that your subject is evenly illuminated. If your subject is not then you have to measure the light falling on different areas of your subject and make compromise.
And NO the incident light meter has nothing to do with middle gray or 18% gray.

runswithsizzers · Oct 21, 2019

The following is from page 23 of "Beyond Basic Photography, a Technical Manual" by Henry Horenstein. We used this book as the text book in a medium format photography class at university.

"Incident light is the light that falls on the subject. It is measured by a light meter with a white diffusing material covering its cell. ... The diffuser is made to absorb just enough light to produce a an exposure reading similar to a gray card reading (or to a general reading of a normal-contrast subject).

To make a reading, hold the incident meter at the subject position and point it back at the camera position. Use the indicated reading without correction. Like a gray card, an incident meter avoids specific subject tones and provides an average reading."

Mr Bill · Oct 22, 2019

Bill Burk said:
'Generally' if you aim the meter at your camera from subject position, and the light hitting the meter is the same light that's hitting your subject, your subject should be properly exposed if ...

I agree. But I prefer to call the situation "frontally lit;" this sort of removes some of the ambiguities.

Once the primary light gets way off to the side you run into issues as to how well the light hits the meter. You can see how it's possible that the light would half-illuminate a dome diffuser, but completely miss a flat diffuser. So the two diffusers, on an incident meter, could give drastically different exposure readings, even though the subject has not changed.

People who live by incident meters might say, "oh, just use the duplex method. Take two readings - one pointed at the camera, the other pointed backwards (or up, etc.), then average the readings. But I can think of a number of ways this can go wrong.

RalphLambrecht · Oct 22, 2019

Ariston said:
I recently picked up an incident light meter and went for a hike in the woods to give it a try. I thought it might provide a short-cut for when I was not in the mood for spot metering. I tested it at home with a digital camera several times before using it for film.

Well, when I developed my roll, the shots I had taken in the woods with the incident meter were mostly underexposed. According to Gossen, I am supposed to point the incident meter from the subject to the camera to record the light falling on the subject from the camera's position. I am wondering if I neglected to pay attention, and maybe some rays of sunlight were shooting through the canopy and hitting the dome of my meter.

Should I instead have simply shaded the dome and taken a reading? What do you guys do? I thought this would provide a simpler solution for times when I wanted things to be simpler...

I use it just like Gossen suggests

Bill Burk · Oct 22, 2019

Mr Bill, That's a good way to look at it.
At some point, the light is coming from a direction that doesn't work well with incident meters (like sunsets), sometimes a spotmeter is better.

wiltw · Oct 22, 2019

If you have a tonal target with white area, mid-tone (18% grey) area, and black areas, using an incident meter in the same light WILL RESULT in an exposure which captures the midtone areaat its inherent brightness while also rendering white as white and black as black. That is, the inherent tonality will be preserved, and you will not capture grayish snow or grayish black cats in the photo!

GLS · Oct 22, 2019

grimp0teuthis said:
digital cameras are not as good at holding detail in highlights

This part has not been true for many years. Modern digital sensors are capable of capturing 14+ stops of dynamic range.

To answer the OP's question: these days I generally only use incident metering if the scene is very evenly illuminated (say on a cloudy day), and even then I still tend to favour spot metering. I use a spot meter 95+% of the time, because you can be much more confident in your metering that way (especially important for slide film).

AgX · Oct 22, 2019

Chan Tran said:
Incident light meter requires that your subject is evenly illuminated. If your subject is not then you have to measure the light falling on different areas of your subject and make compromise.
And NO the incident light meter has nothing to do with middle gray or 18% gray.

I contradict:

-) if the subject is un-evenly lit, then incident metering (or any substitute metering) stilll can take place if one meters for those parts of the subject that are of ones interest. As long as the dome is hit by same light.

-) incident metering is a substitute metering based on the assumption of a 18% reflectance by the subject.
It is the counterpart to reflected light metering off a 18% grey card.
(One may argue that a incident metering with a dome is not an apt substitute for a flat grey-card as for flat objects a flat diffusor (as in reprography) must be used, but one then may argue too that in many cases the flat grey-card is a wrong substitute and a spherical grey patch mut be used...)

For how the meter itself is calibrated we have have to discuss sensitometric issues; I regard such off-topic here.

Chan Tran · Oct 22, 2019

AgX said:
I contradict:

-) if the subject is un-evenly lit, then incident metering (or any substitute metering) stilll can take place if one meters for those parts of the subject that are of ones interest. As long as the dome is hit by same light.

-) incident metering is a substitute metering based on the assumption of a 18% reflectance by the subject.
It is the counterpart to reflected light metering off a 18% grey card.
(One may argue that a incident metering with a dome is not an apt substitute for a flat grey-card as for flat objects a flat diffusor (as in reprography) must be used, but one then may argue too that in many cases the flat grey-card is a wrong substitute and a spherical grey patch mut be used...)

For how the meter itself is calibrated we have have to discuss sensitometric issues; I regard such off-topic here.

Of course you can measure the part of the subject where you're interested. And no there is no 18% gray with incident meter. The 18% gray is the reflected light meter.

baachitraka · Oct 22, 2019

grimp0teuthis said:
An incident meter doesn't give you camera settings for "the correct exposure", it gives you camera settings for placing the light you measured at middle gray. If you meter in bright sunlight, the settings it gives you will consider that sunlight to be middle gray (and your shadows and midtones will be darker/underexposed) and if you meter in a dark shadow, it will consider the shadow to be middle gray (and your shadows will be brighter).

On black and white or color negative film, you want to "meter for the shadows", so take your reading from a relatively shady (but not extremely dark) part of the scene. This is because negative film is good at keeping detail in the highlights when there is a lot of light, but not good at keeping detail in the shadows when there isn't enough light. Slide film and digital cameras are not as good at holding detail in highlights when there is a lot of light.

Try metering in a shady part of the scene. Think about whether you want that shady part to be middle gray, lighter, or darker, and how that will affect the other parts of the scene, then put in your camera settings.

This is one the best explanation.

Another good thing is the shadows can be simulated using palm

baachitraka · Oct 22, 2019

Chan Tran said:
Incident light meter requires that your subject is evenly illuminated. If your subject is not then you have to measure the light falling on different areas of your subject and make compromise.
And NO the incident light meter has nothing to do with middle gray or 18% gray.

Even illumination is not a strict requirement. 18% or 12.5%, the incident meter gives a value to work with it...

AgX · Oct 22, 2019

Chan Tran said:
And no there is no 18% gray with incident meter. The 18% gray is the reflected light meter.

At a meter where you can change the dome/flat diffusor for direct metering you will see that the diffusor itself has 18% transmission.

Thus when metering directly off an 18% grey-card and then doing with same meter an incident metering, you will get same result.

guangong · Oct 22, 2019

For practically all still photography I use a reflective meter, either handheld with wide receptive angle, semi spot in Leicaflexe, or spot meter. Sometimes with LF will use incident meter. When shooting movies, I use incident meter for consistency of results on film, otherwise lighting would appear to change from shot to shot and also not reflect real changes in amount of light.
However, it’s useful to play around with different measuring instruments and compare results. In these comparisons I would include one or more of the various exposure tables. A good way to learn about light. Keep in mind, there was a time when there were no meters.
One thing should be noted: not all meter manufacturers use same criteria for neutral gray.
The learning never stops.

Dan Daniel · Oct 22, 2019

Every meter is a tool, not a soothsayer. Well, I guess a meter is a like a soothsayer, delivering cryptic coded info that you will need to interpret and make work for your situation.

Every meter is dumb. Ask it a simple question, it gives a simple answer. You can add fancy dials and readouts and viewfinders and domes and slides and such, but these are all bells and whistles on top of a very simple dumb tool.

Like every dumb tool invented by humans, it can be useful if one makes use of what it does in a manner that respects its stupidity. A hammer will not tell you how to install a door frame and a meter will not tell you how to expose a scene. That's your job.

ParkerSmithPhoto · Oct 22, 2019

If you used a spot meter with the Zone System, then be sure to check out BEYOND THE ZONE SYSTEM. Takes a bit to get your head around, and it provides methods for both incident and spot metering. I believe that his incident method is actually superior to spot readings.

If you are using a full speed developer like Pyrocat, you might want to overexpose by 1/3 (I rate FP4 at 100 on my Sekonic incident meters). If you are using D76 or the like, you may need to bump that up to a full stop to get your shadows correct. I would suspect that your underexposure was a combo of errant film speed and also metering in a highlight area instead of shadows. Getting a proper exposure in sunlit woods can be tricky. Tons of dark foliage and bark, some in sun, some in shadows. Much easier if a little overcast.

BTW: I'm in Atlanta, too. If you need any darkroom gear, I usually have some extra stuff laying around.

jim10219 · Oct 22, 2019

Spot meters are better for landscapes. Landscapes can have tricky lighting because they often span large areas with harsh light that can provide a wide range of tonal values. Spot meters allow you to figure out a good course for achieving the final image you want, with some knowledge and math.

Incident meters are better for smaller, more contained objects with soft lighting. You can use them for landscapes, but I find them often to be more work than using a spot meter (though in flat lighting, like a very cloudy day, they can be easier to use). With an incident meter, you want to measure the light that's the same as what's falling on your scene. (Almost) Always point the dome towards the front of the camera. It's best if you can actually have meter from the exact point you want to be your focus. If you're shooting a scene where you're concerned about capturing the shadows, make sure to take your reading in the shadow. If you're concerned about the well lit areas, make sure you're measuring in a well lit area. If you're trying to average the two, then you have to take two measurements, one in the shadow, and one in the light, and average the two. If you're trying to shoot an object that is brighter than middle gray, like snow or bright rocks, then you have to compensate for that in your metering. Same with dark objects like tree trunks or dark rocks and dirt.

They can be useful, and I especially like them for portraiture and anything with a flash. Basically anything where the lighting and tonal range is fairly consistent and controlled or predictable. They make those types of shots much easier to meter. But once scenes start to get more complex, they make metering more difficult. They're different tools and each has distinct advantages and disadvantages. Knowing how to use each, their limitations, and how they work is important, especially when using one in a less than ideal situation.

If you want something easier than a spot meter and incident meter for landscape photography, I recommend a reflective meter. They still have some drawbacks, but if you learn how to use them, they can provide a fairly good reading very quickly. Again, you just have to be familiar with their limitations. There are several smart phone apps that are really good for this.

How do you use an incident light meter?

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