Incident light meters question

[Chuck_P]

Not sure that i understand, but...
The incident meter doesn't need to 'compensate' for shadow values, because it 'automatically' allows shadows within the subject to be and remain shadows.

All reflective surfaces only should be as evenly lit as possible if you want them to appear shadow- and featureless in the image you will be creating.
I rarely want such a thing, am very happy instead with the way light 'sculpts' things.

I feel you know what I meant, but let me explain more fully, especially for new analog shooters.

In a sun shade situation, the incident meter will give empty shadows if read in the sun and it will blow the highlights if read in the shadow. Sun/shade situations are usually handled by taking a reflective reading in the shadow and then reducing the exposure one, two, or even three stops------this compensates for the meter wanting make everything middle gray and provides an end result with a shadow value that is more appropriate to the scene and probably one's visualization.

Once the middle value is accounted for by taking the incident reading (or a reflective reading from the gray card), then the gray scale is "set", then all the other reflective surfaces will fall on the gray scale relative to their luminance value. Then development and printing controls can be used to tweak the final contrast.

When I use my spot meter to place a shadow at -2 stops (zone III), then at that point I have fixed the gray scale, then all other reflective surfaces will fall on the gray scale relative to their own luminace value. Then development can be used to increase neg contrast if needed.

So, again, in a sun/shade mix, when the reading is taken in the sun, the incident measurement can't compensate for ensuring that the shadows are provided adequate exposure (but the photographer can by understanding it limitations). Incident meters and gray cards have their limitations when it comes to providing adequate exposure in all areas of the negative, and both are best used when the illumination is relatively even for the bulk of the reflective surfaces in the scene/subject.

 

[Q.G.]

I feel you know what I meant, but let me explain more fully, especially for new analog shooters.

In a sun shade situation, the incident meter will give empty shadows if read in the sun and it will blow the highlights if read in the shadow. Sun/shade situations are usually handled by taking a reflective reading in the shadow and then reducing the exposure one, two, or even three stops------this compensates for the meter wanting make everything middle gray and provides an end result with a shadow value that is more appropriate to the scene and probably one's visualization.

I see what you mean, but i dont think it is correct as such.

When you take two incident readings, one in the shade one in the sun, you will know how the tone values will fall in both shade and sun, and the difference in illumination between shade and sun (the absolute range).

If you point a reflective light meter at both the shaded and sunny part, you would know exactly the same, if only you knew what it was (the tonal value) of what you pointed your meter at.

If you know how to correct the reflected light reading to get the desired result, you will also know how to do the same to the incident light readings.

The same, except (and this is an important difference) you haven't yet taken the tonal value of the thing you pointed the reflecte dmeter at into account. You don't know, and have to figure out, how the thing the meter was pointed at skews the results.

So the only difference between incident and reflected light metering is that (as ever) an extra step is needed when using reflected light metering.

 

[Chazzy]

I don't think what you say is correct. If the subject is, for example, back lit you certainly don't want to meter the backlit portion. You meter on the front of the subject towards the lens.

That's what I have always read—point the dome toward the camera position.

 

[Lee L]

That's what I have always read—point the dome toward the camera position.

2F/2F is working his way around the backlighting objection by saying (rather obliquely) that the light source isn't the backlight anymore in that situation, but the light source is whatever is causing fill on the side away from the backlight. This is a rather awkward and confusing way to state the case, especially when read by a beginning photographer. 2F/2F is also recommending a method for the studio which is more often used to determine lighting ratios, and is rather more suited to a flat incident plate rather than a hemispherical dome receptor on the meter.

I have seen one book that recommends splitting the difference between two readings in a sidelit situation, one reading aimed at the camera and one at the light source. All others I've seen, including meter instructions from Gossen, Minolta, Sekonic, and from Ansel Adams, Phil Davis (his Incident Reading Zone System), and many others indicate that the hemisphere should be in the same light as the subject, pointed in the direction from the subject to the camera.

In the end, a hemispherical receptor incident meter is specifically designed to be used in the same light as the subject, pointed in the same direction as from the subject to the camera. The reason for the hemispherical dome is to get a decent reading of the the light falling on a 3D subject that will be reflected toward the camera. As you gain experience, you might decide to finesse that reading a bit, but it's the place to start, and to stay until you become smarter than your meter.

I never saw anyone in the dozens of studios I worked in use a hemispherical incident dome pointed directly at the light source as a final exposure reading unless the light source was in line with the camera or they were trying to underexpose the shadow side of an object. The meter was pointed with the dome toward the camera.

Lee

 

[Q.G.]

Depends on what you want to achieve.

If the aim is to produce a silhouette, you want the side of the subject facing the camera underexposed, you you do not point the meter/dome towards the camera, but towards the back light.

If you want to have the side of the subject facing teh camera exposed properly, you of course meter the light falling on that side of the subject, and point teh dome towards the camera.

Very often, the light is not falling on the subject from either straight behind or straight opposite the camera.
You then will still see part of the subject lit by the main light from where the camera is. Often (by no means always) the best 'pictorial outcome' is achieved when that bit lit by the main light is exposed properly, allowing the rest to be underexposed.
You achieve that by pointing the meter/dome towards the light source.

In general, you point the meter/dome towards the light illuminating the part of the subject you want to have exposed properly.
(In a silhouette, that bit would be the part you don't see. So then you do point the meter away from the camera, so that the bits that catch the back-light you might still see from the camera, the glowing edges, are exposed properly.)

 

[Steve Smith]

I used to meter the palm of my hand with a Weston before I found a dome for it.

The Weston meter has indicator mark for just this purpose. I think it's the one marked 'C'.


Steve.

 

[2F/2F]

2F/2F is working his way around the backlighting objection by saying (rather obliquely) that the light source isn't the backlight anymore in that situation, but the light source is whatever is causing fill on the side away from the backlight. This is a rather awkward and confusing way to state the case, especially when read by a beginning photographer. 2F/2F is also recommending a method for the studio which is more often used to determine lighting ratios, and is rather more suited to a flat incident plate rather than a hemispherical dome receptor on the meter.

I am not "working my way around the backlighting objection", Lee. I mentioned it specifically in my original post, so I have discussed it from the start.

What I said is that the source that is lighting the front of the subject is the main light, not the brighter back light. A back light is exactly that: a light in back of the subject. Intensity has nothing to do with it in this extreme of a case (approximately 180 degrees from each other). The main light is the main light that is illuminating the photographed part of the subject, whether it be reflected or direct, and the back light is the light lighting the back of the subject, regardless of quality of light or intensity of light. As long as it is not the solitary light (silhouette), the back light is not the main light, even if it is the brightest light, and even if the source of the backlight (e.g. Sun) is also the indirect source of the reflected light that is lighting the photographed part of the subject (e.g. reflected Sun).

If you want to expose for the front of the subject, point the dome at whatever is illuminating the front of the subject. If you want to expose for the back of the subject, point the dome at whatever is illuminating the back of the subject. Why would you meter the back light if you want an exposure for the front of the subject? I NEVER suggested that in any way. The issue is that the other fellow is calling the back light the main light in this situation, when it is not. In an outdoor situation in which Sun is lighting the back of the subject, and reflected Sun is lighting the front of the subject, Sun is NOT the main light, even though it is the brightest light, and even though it is the indirect source of the light that is lighting the front of the subject.

The way that what I suggested would work in the studio is that, with the fill in place to allow metering of its bleed/flare, I would meter with the dome pointed at the main light, not at the camera. I want to expose for the main light source, not for the average of the main and whatever fill there might be. In the studio, taking two readings from two different sides of the face, and then averaging them is the same as taking a centrally located reading. I don't want to expose in the way that this centrally-located reading would tell me to expose. I want to expose for the main light, so that I get the exposure I want there. I don't want to expose for the fill light at all (except in the way that it bleeds/flares onto the main-lit part of the subject). I only want to adjust the fill to achieve the desired difference in incident light from the main light, not actually factor it into the exposure.

Yes, there are better grids (flat) to use to precisely measure lighting ratios (or a spot meter), if that is what you want to do, but the dome certainly gives you a quick idea, and is accurate enough. Knowing an absolute lighting ratio is not as important as being able to quickly adjust the fill to the roughly-desired level (e.g. one or two EVs, or "stops" dimmer than the main). To do this, I get the lights how I think they should look by eye, then meter the main, with the fill in place. Then I move the meter to the fill side, and see how far down the needle moves. If it moves down too far for what I want, I move the fill closer. If if does not move down far enough for what I want, I move the fill farther away.

The more extreme the lighting ratio desired, the more important it becomes to point the dome at the main light. A centrally-located ("at the camera") reading in an imbalanced (i.e. non-1:1) lighting ratio will overexpose the film, plain and simple. When using a centrally-located reading, the more extreme the ratio, the more extreme the overexposure. The only time I would use a centrally-located reading would be when I was aiming for a 1:1 ratio (or when ambient conditions - such as flat light - dictated a 1:1 ratio).

This is the way I have always been taught to use an incident meter, in every photo class, beginning or advanced, and the point was hammered home repeatedly (and vehemently) in various lighting classes. It works, and not only that, but it makes total sense when you think about what an incident meter does. I realize the common rule to thumb/instruction is a bit different, AND that this is the way that most photographers use the meters. However, that method makes little sense to me except as a brief "rule of thumb" explanation to beginners, and we all know that what most people do is usually the "wrong" thing. Have I ever actually seen another photographer metering the way I suggest in "the field"? Absolutely not...but then again, I have never seen a photographer of the level of professionalism and technical expertise of some of my past instructors at work on a professional job. People I trust and respect on a technical level (even if not an on artistic level) taught me to meter this way, not rules of thumb. Rules of thumb are not be alls and end alls. They are a starting point to get people passable results quickly, and hopefully for independent study and evaluation on one's own.

Q.G. explained it perfectly when he said: "In general, you point the meter/dome towards the light illuminating the part of the subject you want to have exposed properly." It is as simple as that.

 

[Poisson Du Jour]

Whatever you are metering with — incident, reflected or spot, it is calibrated at Zone V, the so-called "middle grey" value. That reading is taken as a baseline reference from where you deviate + or – to suit the conditions. You must use judgement as to what to accept from the meter's recommendation and which way to deviate from that recommendation.

It is correct that an incident reading should have the meter facing the direction of the camera, especially in point-light illumination. If the scene has diffuse (e.g. flat or overcast) illumination, an incident reading can be made anywhere, not necessarily facing back to the camera.

Where clearly delineated shadow and highlight areas exist, spot metering, not incident is a better method to assess the areas where detail is required in shadows and highlights. This method accounts for principal luminances in the scene you have, rather than assume the entire scene is an 'average' one. Once all hi/lo areas have been assessed, average them; the meter's Average/Ev= or baseline Mid-tone from a grey card will do this, or dissect scene readings mentally.

 

[johnnywalker]

Q.G. explained it perfectly when he said: "In general, you point the meter/dome towards the light illuminating the part of the subject you want to have exposed properly." It is as simple as that.

The manuals I have for my Gossen incident meters both say to point the meter from the subject to the camera. Do either Q.G. or 2F/2F have a published reference for your alternative method?

 

[jmal]

Whatever you are metering with — incident, reflected or spot, it is calibrated at Zone V, the so-called "middle grey" value. That reading is taken as a baseline reference from where you deviate + or – to suit the conditions. You must use judgement as to what to accept from the meter's recommendation and which way to deviate from that recommendation.

It is correct that an incident reading should have the meter facing the direction of the camera, especially in point-light illumination. If the scene has diffuse (e.g. flat or overcast) illumination, an incident reading can be made anywhere, not necessarily facing back to the camera.

Where clearly delineated shadow and highlight areas exist, spot metering, not incident is a better method to assess the areas where detail is required in shadows and highlights. This method accounts for principal luminances in the scene you have, rather than assume the entire scene is an 'average' one. Once all hi/lo areas have been assessed, average them; the meter's Average/Ev= or baseline Mid-tone from a grey card will do this, or dissect scene readings mentally.

I really think this is what I as after initially. And, if the incident meter gives a general middle gray for the entire subject, how does one determine how to place the desired area of the subject in the desired zone? It seems a spot meter (or a normal reflective meter with a narrow enough field) is the best way to achieve this. Granted, in most situations an incident meter probably works great. I'm not an absolute zone system guy and have often photographed antithetically to it, but I do like the idea of being able to pick a shadow area, place it where I want it, and adjust development based on the highlights. I guess I have a hard time understanding how one would do this with an incident meter. How would one control a specific zone, particularly if one cannot get near the subject?

 

[Poisson Du Jour]

The manuals I have for my Gossen incident meters both say to point the meter from the subject to the camera. Do either Q.G. or 2F/2F have a published reference for your alternative method?

I agree with you. There are some strange statements being put in this thread.

Yes, a simple explanation and reference, rather than a haemorrhaging welter of words that no doubt is completely be lost on a beginner. What's appropriate to studio use is certainly not appropriate to outdoor use. Anybody with a degree in visual arts will tap you on the shoulder to point this out.

 

[Chuck_P]

If you know how to correct the reflected light reading to get the desired result, you will also know how to do the same to the incident light readings.

We can agree on that, no question. But what I have said is absolutely correct----it is metering 101, basic understanding of the middle gray standard and the intelligent use of an incident meter, IMO.

A brief example would be an incident reading on an overcast day where the separation of shadow and highlight is narrow (which is where I want it to be when I'm using an incident meter i.e., uniform illumination primarily). The goal is to get the information on the negative in the right proportions for the intended result. This is going to require a boost in negative contrast. I would take the incident reading on my Gossen, null the reading to "0", then back the dial up to -1, -2, or -3 (depending of course) to reduce the exposure to those shadows to make them less dense on the negative, and bump the development by roughly 25% to increase the density in the highlights. The middle values will print readily and be receptive to other contrast controls in printing. This example does not blindly accept the meter reading, which would have been accurate and rendered values that yielded an informative print, but aesthetically, the measurement needed some outside input.

Now, I am not familiar with BTZS metering that is done with incident readings, so remember that I am not suggesting there's only one way to use an incident meter, only a wise way to use one.

I'm overdrawn, but good discussion, I think.

 

[Q.G.]

There are certainly more ways to skin a cat.
One thing though that you repeatedly put forward is that incident metering would be for flat, "uniform" lighting situations.
It isn't. Why would it be? It works equally well in all situations.

It is true that to get to know the contrast range, pointing a reflected meter at the darkest and brightest point would be the quickest and easiest way. There are good reasons why most meters offer both metering methods.

But that wasn't what we were talking about. It was about how incident metering wouldn't "compensate for shadow values", which would be a reason, it was suggested, why scenes need to be lit as flat as possible.
That's not so. Incident light meters and reflective light meters are good for all sorts of light.

Anyhow, i think that though this thread has not yet resulted in a clear conclusion, everythings that needs to be has been put forward.

Except perhaps the question about texts about how to use a meter, an incident meter in particular.
I must say that i don't know any advanced text on metering at all. Adams probably wrote a bit on the subject.
But don't let that make you think that what was said by 2F/2F is not true. It is.
I believe i entered this thread pointing out that the way to use a meter depends on what you want to achieve. To use a meter effectively, you must understand how it works, so you know how to make use of or get round the particular way these thingies work. And that is more complicated (though not difficult) than the meter manual's " reflected: point at the subject", "incident: point at the camera".
Using a meter is like using any instrument. There are many different ways to use it effectively, and the one leads to what you hope to achieve is the best. Which or whatever way that might happen to be.
You can strike a key on a piano's keyboard in many ways. A manual saying you should hit it hard to make a loud sound, lightly to make a soft sound, though explaining how the thing works absolutely correctly, is still not even beginning to cover the basics.
So my answer would be: don't look for books as if only they hold the Truth. Consider what was said, and see what there is in there that you could use to suit your needs.

 

[Brandon D.]

I really think this is what I as after initially. And, if the incident meter gives a general middle gray for the entire subject, how does one determine how to place the desired area of the subject in the desired zone? [...]

An incident meter does not see a subject. So, it cannot even consider the tonality of a subject. It only sees the light falling on its dome.

So, in theory, under even lighting an incident meter will recommend an exposure setting that will make a black cat appear black (e.g., let's say it gives us ISO 200, 1/60th, F/4). In that same lighting, it will recommend the same exposure setting and it will make a white cat appear white (e.g., ISO 200, 1/60th, F/4). And, again, under the same lighting it will recommend a setting that will make a gray cat appear gray (e.g., ISO 200, 1/60th, F/4). Under the same lighting, it will give you the same reading regardless of what's in the scene.

Again, an incident meter does not consider the subject, only the light level falling upon its dome. In my experience, I primarily use it to get an exposure reading that will produce an image similar to what I see in the scene (e.g., black cats should be black, white cats should be white, gray cats should be gray, and etc.). I never think about middle gray when I'm using an incident meter. If I'm worried about middle gray, then I use a spot meter.

 

[jmal]

Semantic quibbles aside (all meters have to arrive at a reading that will result in some kind of average reading, be it reflected light or incident light), how does one control an incident meter if there are distinct shadows and highlights? What if the sun is very bright, but there are also many shadow areas that I want to capture? Surely in these kinds of conditions, an incident meter will give a reading that needs to be adjusted, not simply one that represents the way the eye sees. How does one adjust if there is no reference point such as a portion of the subject set to zone xyz (in a reflected light metering)? Also, perhaps many of the responses are leaning toward a more general audience than myself, but I hardly consider myself a beginner. I simply have never used an incident meter.

 

[Barry06GT]

.
This is all part of being a photographer; using a meter and understanding what to do with the information. Photography is all about solving a problem.

Digital cameras made any fool a "photographer". Point it in the general direction of something, trust the (automatic) meter and autofocus, push the button a few times, and select the one from the twenty that does not suck as much as the others.

My point is that there is no one answer. Use your meter, look at the results, then make corrections and get better results. Most of the people on this list do this stuff without thinking too much about it: it becomes instinct, second nature.
.

 

[johnnywalker]

Post 39 by D. Brandon is my understanding of incident metering and I think explains it very well.

 

[Eric Rose]

Well I've been using an incident meter for over 40 years and I do it pretty much the way 2F/2F does. Why walk over to the subject if it's in the same light as the camera. I'm just lazy I guess. The only time I don't use my reading from the camera position is if the subject is not in the same light.

If it's important I use spot to determine my SBR but not to place zones unless I decide to get anal about some shadow stuff in a very high SBR situation.

In the studio I use the same methods as 2F/2F. In this case I use a flat disk rather than the dome.

If I'm shooting 35mm or MF I quite often don't even use a meter. Heck after all this time if I can't hit it pretty close I might as well pack it up.

 

[Larry Bullis]

All this stuff about pointing the incident meter at the light source reminds me of a guy I used to teach with. He was teaching the "reading the palm" method. He insisted that you should move your hand and the meter around until it registered the greatest amount of light and base your exposure on that. Of course, the students all underexposed their film when they did it. And he was a commercial photographer who was (somehow) fairly successful. But then, he hung it up and got himself tenured in a commercial photography school.

I told them to hold their palms parallel to the film plane between them and the subject and suddenly they got it right. I told them not to tell him I did that. It was our secret. I let him take the credit.

I'm just really happy that I don't have to carry all that stuff around in my head, or maybe I should -- Just take the computer with me and work out incredibly complex algorithms. There's a really simple tool that I think is a LOT better than that, and you don't point it at the light either, because it won't work - for about the same reason. It is the reflected light meter, and for it to work right, it needs to see the subject as the camera does. Point it directly away from the camera toward the subject even if you are reading close up, because you are reading the light as the camera sees.

Frankly, I'd much rather shoot pix than rack my brains and do higher math. I'm a count it on my fingers kind of guy. Common sense usually works best.

However, we all have our ways of working and I'm sure as hell not about to tell anyone how to work if they disagree with me. If it works for you, then use it, and I wish you the best. Maybe I'm wrong, but my exposures are usually pretty close to right on. What's wrong with that?

 

[Larry Bullis]

An incident meter does not see a subject. So, it cannot even consider the tonality of a subject. It only sees the light falling on its dome. ...

You have it right. I didn't quote your whole response, for brevity, but the operative term you use is "even light". An incident light meter is limited for that reason. If you want to read shadows, complex multiple light scenes, etc. with an incident meter, I guess you can, but WHY? Why not use the reflected light meter, which is simpler, requires a lot less mental gymnastics...

I suppose that for people who enjoy that stuff, its fine. I don't have time for it, and if I'm going to expend mental energy on that level, I'd rather be working on the problem for which the answer is "42". After 46 years of intensive work in photography I'll keep doing it if it's fun. If not, I'll draw on animal skins with a burnt stick.

 

[Brandon D.]

I simply have never used an incident meter.

Understandable. I didn't know what an incident meter was for until after I bought one. And, I quickly learn that an incident meter has a totally different application than a reflective meter.

Someone using an incident meter should only do so with concern about the way light is falling upon the objects of the scene. It's very useful when there are mixed light qualities or sources falling into the scene if you have patience and time on your side. On the other hand, someone using a reflective meter should only do so with concern about the reflectivity of the objects in the scene.

Semantic quibbles aside (all meters have to arrive at a reading that will result in some kind of average reading, be it reflected light or incident light)

This is not a semantic quibble. It's a clarification of function and application. In general, both bicycles and speed boats get you from one place to another. However, you would not use a bicycle to travel across a lake and jet ski. And you wouldn't use a speed boat to go around delivering newspapers on a neighborhood paper route. You don't seem to understand why a photographer would use an incident meter vs. a reflective meter, which is the most important thing to understand if you have never used an incident meter.

While reflected meters and incident meters serve the same general function in that they both recommend exposure readings, they actually serve different applications. Reflected light and incident light are not the same kind of light, which is why they have their respective meters.

 

[Brandon D.]

how does one control an incident meter if there are distinct shadows and highlights?

You wouldn't control the incident meter. Instead, you would control, or manipulate, the light falling into the scene. Maybe you add reflector to bounce more light into the scene, maybe you add a black reflector to block light from falling into the scene, or maybe you add fill flash to add light somewhere in the scene. Or, maybe you deal with the issues in post-production.

But, again, you don't deal with the meter. You deal with the light coming into the scene when you're using an incident meter. The incident meter just does its job, i.e., measures light falling into the scene. It doesn't fix problems, it only gives you data about the light levels/ratios falling into the scene. The photographer is what solves the problems, , using his/her understanding of the way light falls into a scene, instinct, intuition, modifiers, post-production, and etc.

That said, a photographer using an incident meter is usually going to be more concerned with achieving contrast equivalent to the scene they actually see or that they are artificially modifying/creating using flash photography, reflectors, or etc.

What if the sun is very bright, but there are also many shadow areas that I want to capture? Surely in these kinds of conditions, an incident meter will give a reading that needs to be adjusted, not simply one that represents the way the eye sees.

The answer to that line of questioning depends on where you take the meter reading from. Remember, in my previous post where I used the example of the black cat, the white cat, and the gray cat, all cats were under the SAME level/quality of light (i.e., ISO 200, 1/60th, F/4 to refresh your memory). They were NOT in a scene with MIXED light levels (e.g., shade in one part of the scene and sunlight in another part of the same scene, as you suggest in your questioning).

Again, when you do have mixed light levels in the same scene, the incident exposure reading will depend on where you take the meter reading from and the level of light in that area. But, believe it or not, the incident meter will give you a reading that will render the area in the scene that you're metering similar to what your eyes see. For instance, let's put our black cat and white cat near a tree together. Let's say that the white cat is lit by sun light while the black cat is lit by shade. Taking a meter reading in front of the white cat lit by sunlight will give you a reading that will render the white cat bright white, similar to how it would appear to the eye. Taking a meter reading in front of the black cat lit by shade light will give you an incident reading that will render the black cat dark, similar to how it would appear to the eye.

Because each subject in the scene is being lit by DIFFERENT light sources, you WILL get different readings, as opposed to the example in my previous post where the cats were all lit by the SAME light source. If there are any "problems," then the photographer using the incident meter would manipulate the light until he/she gets desired light ratios.

Regardless, with an incident meter, a black cat will always be black when you're metering the light falling upon the black cat. And, a white cat will always be white when you're metering the light falling upon the black cat.

Thus, if you meter a black cat in shade light, it will appear to be a black cat in shade in your photo. If you meter a black cat in sun light, it will appear to be a black cat in sun light in your photo. If you meter a white cat in shade, it will appear to be a white cat in your photo. If you meter a white cat in sun light, will appear to be a white cat in sun light in your photo.

But, again, you don't adjust the incident meter because all it is supposed to do is give you feedback on how light is falling into the scene. The adjustments are made to the scene itself or to the image in post-production.

The meter I use allows the user to save several meter readings into memory so that they can be "averaged" into one reading. In my experience, it has proven very useful in some cases but not in all cases. In every real world situation, there's no guarantee that resulting average exposure is going to render the scene exactly the way you want it to look. So, it's not something you can blindly rely upon. You, sort of, have to develop your own intuition and metering techniques that suit your needs.

How does one adjust if there is no reference point such as a portion of the subject set to zone xyz (in a reflected light metering)?

The question is unanswerable (with respect to the type of answer you seem to be looking for).

AFAIK, there is no full proof metering trick that you can use to "adjust" the incident exposure in any given contrasty lighting scenario to an exposure value that you will always approve of. So, you have to experiment with an incident meter, learn how it responds in real world situations, and then develop an intuition for complex lighting scenarios.

But, most importantly, you have to have a really good reason to use an incident meter in the first place (rather than a reflective meter), otherwise you will waste time and get confused. Someone using an incident meter is more likely going to be more concerned with achieving "contrast relative to the scene" rather than "a perfect exposure." And if you're planning on learning how to use an incident meter, begin learning with simple, evenly lit scenarios -- don't jump right into a complex scenario without getting a feel for what an incident meter does in a simple scenario first.

When using an incident meter, the reference point cannot be established from the subject or any other object in the scene. The reference point is the light falling into the scene (e.g,. shaded light, sun light, cloudy light, tungsten light, fluorescent light, candle light, bounced light, and etc. <--- those are your references).

If you're taking a photo of a yellow taxi cab on the street, the incident meter should recommend a meter reading that renders the yellow (of the taxi cab) as it appears under the illumination of the light falling upon it (depending on where you take the meter reading).

If, for instance, the front end of the taxi cab is lit by sun light and if you take a meter reading in that area, the meter will suggest a reading that will give you a picture similar to the way you see that front end of the taxi cab with your own eyes. In your photo, you'll see bright yellow and the presence of sun light. The incident meter won't "care" about the other parts of the scene (e.g., the shadows) because the meter can only evaluate one place at a time.

However, if the back end of the taxi cab is lit by shade light and if you take a meter reading in that area, the meter will suggest a reading that will give you a picture similar to the way you see the back end of the taxi cab with your own eyes. In your photo, you'll see darker yellow and the presence of shady light. And, again, the incident meter won't "care" about the other parts of the scene (e.g., the highlights) because the meter can only evaluate one place at a time. So, the front end of the taxi cab may show blown highlights if it falls outside of the dynamic range of your capabilities.

What a photographer with an incident meter does in such a scenario is measure the shadows (i.e., the light falling upon the back end of the cab) and records the reading. Then, the photographer measures the highlights (i.e., the light falling upon the front end of the cab) and records the reading. With that data, the photographer can manipulate the lighting in the scene or make adjustments during post-production. But, it is the ratio of light that the photographer is concerned about, not the reflectivity of the objects in the scene.

Because of the limitations of incident meters, it makes more sense to use a reflected meter when using the Zone System in many cases. The type of meter I use depends on what I'm shooting and how I shoot it; so I use both meters.

 

[Brandon D.]

You have it right. I didn't quote your whole response, for brevity, but the operative term you use is "even light". An incident light meter is limited for that reason. If you want to read shadows, complex multiple light scenes, etc. with an incident meter, I guess you can, but WHY? Why not use the reflected light meter, which is simpler, requires a lot less mental gymnastics...

I suppose that for people who enjoy that stuff, its fine. I don't have time for it, and if I'm going to expend mental energy on that level, I'd rather be working on the problem for which the answer is "42". After 46 years of intensive work in photography I'll keep doing it if it's fun. If not, I'll draw on animal skins with a burnt stick.

Yeah, haha, I know I have to be very careful and specific with my jargon or someone will hit the roof, . Hence, the use of "even light."

When there's even lighting and if I'm not using the Zone System, then I usually use the incident meter. I actually use an incident meter nearly every time I like the way the light is already falling upon my subject. Probably, the greatest benefit that using an incident meter has given me is that I've learned to look for lighting that I like. Plus, I'm more aware of the way different light sources act when they fall upon scenes, and so I learn to embrace light sources for what they do. I think most photographers would be surprised about the amount of great looking light that is already out there.

Also, since I do some flash photography, my incident meter also doubles as a great flash meter. Even if you're using flash for fill lighting, the incident meter comes in handy.

And, one of the other limitations of an incident meter is that you have to be in reach of the part of the scene you're metering. With a reflective meter, you can usually stand a long distance away from the scene and do a lot of useful metering. But, most importantly, both meters can be very useful and accurate.

 

[Brandon D.]

The late photographer/teacher Dean Collins explains "subject tonality" vs. "incident lighting (a.k.a., diffuse exposure) " in very simple terms:
http://www.youtube.com/watch?v=JyzkWxtKWm8

Using incident meters, he demonstrates how a single-toned subject is presented/shaped simply based upon the light falling upon it. Pay close attention to what he says about "relative 3-dimensional contrast" and what he says about "specular highlights vs. shadows."

Using an incident meter has a lot more to do with how the source(s) of light themselves make the subject appear according to the lighting scenario at the time.

 

[Q.G.]

Semantic quibbles aside (all meters have to arrive at a reading that will result in some kind of average reading, be it reflected light or incident light), how does one control an incident meter if there are distinct shadows and highlights? What if the sun is very bright, but there are also many shadow areas that I want to capture? Surely in these kinds of conditions, an incident meter will give a reading that needs to be adjusted, not simply one that represents the way the eye sees. How does one adjust if there is no reference point such as a portion of the subject set to zone xyz (in a reflected light metering)? Also, perhaps many of the responses are leaning toward a more general audience than myself, but I hardly consider myself a beginner. I simply have never used an incident meter.

You simply meter the sun and the shade (remember that you carry your own with you all the time).

A reference point is needed only if the metering method can be fooled into thinking that a black thing is not black, etc.
Incident light metering assumes nothing of the sort. It will 'allow' things that are black to remain black in the image, things that are white to remain white, things that are somewhere in between to remain wherever they are in between.

But if you really want to have a specific part of the scene appear in a particular zone no matter what its own tonal value might be, switch to reflected light metering, meter just that bit, and adjust the result.

As mentioned before, there is a reason why most meters offer both metering modes.