Reflective vs. incidence meter reading??

stradibarrius said:

I don't think I have ever seen a camera with an "incidence" meter built in????

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It's not common, especially now, but my Kodak Retina Reflex cameras are fitted with Gossen meters. They came with plastic diffusers to clip on the front to take incident readings.


Steve.

stradibarrius said:

Of all my cameras my RB67 is my favorite and I need to learn to use my hand held effectively with this camera. I shot a roll of film yesterday and exposed each still life scene based on the reflective reading and then the next frame on the incident reading. I am thinking this will teach me something?????

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I'm sure it will.

I know you have asked about personal EI in other threads and your metering technique is an integral part of deciding on a personal EI so I'll make this comment here.

Given you using lights, my expectation would be that the incident meter would provide consistent results and the reflective meter would ask for changes to the exposure based on the composition, i.e. darker compositions will ask for more exposure and vice-versa.

You may like some of the incident metered shots better, that's okay but take the next step.

With the incident meter's consistency you may find the incident metered negatives are generally a-bit-too-thick or a-bit-too-thin to print the way you like.

If this is true you adjust your personal EI (the ISO setting on the meter) to match your incident metering for that film to your preferences.

Steve Smith said:

It's not common, especially now, but my Kodak Retina Reflex cameras are fitted with Gossen meters. They came with plastic diffusers to clip on the front to take incident readings.


Steve.

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Point for clarity here.

When any meter is pointed at the subject from the camera position, even an incident meter, it is being used to measure reflected light.

To measure incidental light any meter must be in the same light as the subject and be pointed at the camera position.

On occasion, when using my Nikons, I will walk up to my subject then turn back toward my camera position and meter the scene with the camera or the sky in that direction. In this case I'm using my cameras "reflective meter" as an "incident meter."

This is far from perfect because of the various patterns a camera's meter uses but if you have practiced and know what to expect it is very workable.

CPorter said:

But using the incident meter in sun/shade mix situations will overexpose the high values if read in the shade and under expose the shadow values if read in the sunlight.

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These are not real good negative scans but the point is conveyed---some examples of this point about incident metering.

There is obviously more light than dark in this subject. But when composing the third shot, I made sure the center-weighted meter of the camera was influenced more by the dark shaded area. The meter's outer, less sensitive regions were also a factor in determining the exposure, just not as much, but ultimately gave a more satisfying result.

Taking an incident reading in the sun and then the shade could have been done and then expose for the average reading. That would probably be the better use of an incident meter IMO, since it does take into account acutal reflective values at both the dark and the light end of the range. It actually attempts an average exposure rather than letting the reflective meter alone try and average the scene, which can lead to some pretty poor exposures if the scene is nowhere near average.

Steve Smith said:

It's not common, especially now, but my Kodak Retina Reflex cameras are fitted with Gossen meters. They came with plastic diffusers to clip on the front to take incident readings.

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The very first Nikon F metering prism, the Photomic, also came with an incident attachment.

In my opinion, there is no better discussion of reflected light metering vs. incident metering than will be found in the Phil Davis book, "Beyond the Zone System". Those who desire a comprehensive, but accessible, discussion of the nuances of both methods might avail themselves to the relevant materials. I would like to add that complicating the issues involved in metering is the fact that, as the late Mr. Davis so elegantly wrote, the "meter cell assumes that the world is bathed in a 5-stop range of uniform, shadowless light, but the calculating dial....assumes that the cell's readings relate to the real world where shade and shadows are ever-present and where 7 stops is the norm". He goes on to point out that there is a discrepancy in "what the cells measures and what the dial does with those measurements"...what follows is a simply way to determine the SBR of a scene, and how to use such information to achieve the "correct" development of one's film ( based upon previous tests of one's own materials ). Mr. Davis does take pains to point out that BOTH metering methods have application and relevance, but both must be used with understanding and insight.

The quick solution to the conundrum raised by Mr. Porter ( as described by Mr. Davis ) is to decrease the exposure by one stop if one has only a shadow reading, and increase the exposure by one stop if one has only a single highlight reading.

markbarendt said:

On occasion, when using my Nikons, I will walk up to my subject then turn back toward my camera position and meter the scene with the camera or the sky in that direction. In this case I'm using my cameras "reflective meter" as an "incident meter."

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No, to claim that this is an incident reading is to completely misrepresent what in incident reading is. This method is using the camera in reflective reading mode to read the correct exposure for the scene you're pointing at. An incident reading detects the amount of light falling on the subject, not the amount of light reflected from the camera position as seen from the subject, which is what you're describing. To achieve an actual incident reading with the camera in this way, you need something like an Expo-Disc over the end of your lens to get a proper incident reading. It needs to emulate a gray card through reduced light transmission and proper color balance.

You also need to watch yourself and test with the matrix metering Nikons (and similar) and an Expo-Disc because they bias exposure based on light levels and contrast, so they may not do that well at low or high light levels using an Expo-Disc. Using spot or center weighted averaging mode with an Expo-Disc should be more accurate than matrix-metering.

Lee

Agree wholeheartedly with Mahler-one's take on Phil Davis' incident metering methods. Well worth reading just to understand the proper usage of incident meters, even if you don't use Davis' incident zone system.

Lee

CPorter said:

Taking an incident reading in the sun and then the shade could have been done and then expose for the average reading. That would probably be the better use of an incident meter IMO, since it does take into account acutal reflective values at both the dark and the light end of the range.

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Another point for clarity.

CPorter illustrates a great point here in that it takes judgment to use any meter properly.

BUT, incident metering NEVER, NEVER, NEVER, takes into consideration the reflectivity of the surface.

Plain and simple, the meter can't even see the reflective surface because it is BEHIND the meter.

I'm not saying CPorter's method is not workable, just different.

CPorter's point is essentially about defining your exposure placement based on what is important to you.

What is important to you depends on what's next. An example from my world.

In the situation CPorter presents I would use my incident meter unshaded a foot or two from the wall, pointing the meter's dome at the camera and set the camera with that reading because the setting the meter would suggest there would place that middle gray sat dish exactly in the middle of the exposure.

So what's next?

This negative, for say Delta 400, would give me easily about 4-stops of detail on either side of middle gray with the normal manufacturer's recommended development times, temps, and agitation.

Well I'm not normal except with temperature and I've tested my stuff and tailored my own process to get results I like better.

To insure I get good shadow detail in shots like this my development time is what others might consider proper for N+1 or a one stop push.

To protect the highlights and avoid over-development I reduce my agitation considerably. With Xtol that means 1 inversion every 2 minutes instead of 5-7 every 30 seconds.

What's after that?

The enlarger and I just didn't get this next point until I got an enlarger. It is why film is soooo flexible.

I get to make a tailor and control a whole new exposure specifically to get the very best from that negative onto paper.

Lee L said:

No, to claim that this is an incident reading is to completely misrepresent what in incident reading is. This method is using the camera in reflective reading mode to read the correct exposure for the scene you're pointing at. An incident reading detects the amount of light falling on the subject, not the amount of light reflected from the camera position as seen from the subject, which is what you're describing. To achieve an actual incident reading with the camera in this way, you need something like an Expo-Disc over the end of your lens to get a proper incident reading. It needs to emulate a gray card through reduced light transmission and proper color balance.

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My point for that post was that if you want an incident measurement you have to measure the light falling on the subject not the light at the camera position.

Your Expo disk suggestion is great BTW, as a quick and dirty emulation of that I defocus as far as possible.

Lee L said:

You also need to watch yourself and test with the matrix metering Nikons (and similar) and an Expo-Disc because they bias exposure based on light levels and contrast, so they may not do that well at low or high light levels using an Expo-Disc. Using spot or center weighted averaging mode with an Expo-Disc should be more accurate than matrix-metering.

Lee

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You are absolutely right with your caveats here, this technique takes real thought and a grain-of-salt.

markbarendt said:

In the situation CPorter presents I would use my incident meter unshaded a foot or two from the wall, pointing the meter's dome at the camera

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What? That's exactly what I did!

I placed the dome in the shade of the dish while pointing the dome toward the camera. And I placed the dome in the sunlight in front of the wall while pointing the dome toward the camera.

You somehow think that I pointed the meter's dome toward the wall in that example?

When I said "incident reading taken here", it means just that, an incident reading.

CPorter said:

These are not real good negative scans but the point is conveyed---some examples of this point about incident metering.

There is obviously more light than dark in this subject. But when composing the third shot, I made sure the center-weighted meter of the camera was influenced more by the dark shaded area. The meter's outer, less sensitive regions were also a factor in determining the exposure, just not as much, but ultimately gave a more satisfying result.

Taking an incident reading in the sun and then the shade could have been done and then expose for the average reading. That would probably be the better use of an incident meter IMO, since it does take into account acutal reflective values at both the dark and the light end of the range. It actually attempts an average exposure rather than letting the reflective meter alone try and average the scene, which can lead to some pretty poor exposures if the scene is nowhere near average.

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On the third shot, if you had taken an incidence reading agint the siding and then in the shadow behind the dish would the average have been the same as the third, center weighted shot?

CPorter said:

What? That's exactly what I did!

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I was not trying to suggest anything otherwise, just trying to keep my thoughts clear.

stradibarrius said:

On the third shot, if you had taken an incidence reading agint the siding and then in the shadow behind the dish would the average have been the same as the third, center weighted shot?

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Did you say you had a Gossen Luna Pro? Set it to 1/250 at f8 and you'll see there are three stops between the shadowed reading and the sunlight reading.

The shadow reading was 1/250 at f8 and the sunlight reading was 1/250 at f22. Taking the exact average would be 1/250 at and halfway between f11 and f16 on the dial. So, I guess on my Canon Rebel X, I would have set the average at 1/250 at f13, pretty close. This would have given just a bit more exposure to both the shadow and sunlit area.

It should be kept in mind though, that this is a very simple scene with basically two main reflective surfaces. Using the incident meter to average the high and the low light levels, while I think is a good way to use it, still does not give you an idea of the many reflective surfaces that makes up most scenes. In that respect, the spot meter is the best tool IMO, to zonies like myself, it affords the greatest amount of control. To others into the BTZS system, the incident meter is the tool of choice I believe.

markbarendt said:

Point for clarity here.

When any meter is pointed at the subject from the camera position, even an incident meter, it is being used to measure reflected light.

To measure incidental light any meter must be in the same light as the subject and be pointed at the camera position.

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Yes. With the adaptor on the Kodak, you move the camera to the subject and point it at the camera position (the position of the camera before you moved it to take the reading!).


Steve.

CPorter said:

That would probably be the better use of an incident meter IMO, since it does take into account acutal reflective values at both the dark and the light end of the range.

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Markbarendt has made a good point in an IM to me. I did not mean to imply that an incident meter takes into account reflective values, although that's what I said precisely (a plain case of poor choice of words). I wanted to say that it does start to hone in on the actual SBR of the scene, only not in actual reflective values, but only in the extremes of light intensity in the scene.

It was a good catch Mark.

Chuck

"To measure incidental light any meter must be...pointed at the camera position."

I keep hearing this repeated everywhere I go. What is the logic behind it? Why would you point an incident meter at the camera if your aim is to measure the light falling on the subject?

The best argument I have got so far is that the instruction booklet for the meter says to do it.

Do we learn the ideal methods to photograph from our equipment instruction manuals? They are some of the most abridged, non-technical, rule-of-thumb-filled (and often poorly translated) pieces of photography literature out there.

Do you want to measure the light that is coming from your camera's position, or do you want to measure the light that is illuminating your subject? In some cases they may be the same light, however, this does not make the "at the camera" method a correct rule of thumb. It simply means that it works in situations in which the same light that is illuminating the back of the camera as is illuminating the subject.

The contrastier the light, the more important it becomes to meter the main light source itself to determine the proper exposure. On a flat day, "at the camera" will work...but don't think of it as "at the camera". Think of it as "at the source of light", which on a flat day is the same thing at "at the camera".

Take a studio situation with a 2:1 lighting ratio, assuming the subject is a person looking straight at the camera. You have three options:

1. Meter from the main-lit side of the face toward the main light.
2. Meter from the fill-lit/unlit side of the face toward the fill light (or no light).
3. Meter from the middle by pointing the meter straight ahead from the subject's nose (at the camera in this particular composition).

Work through this and figure out which method is "best" for giving you the exposure that will render the lighting as you crafted it to be in the studio. (Remember that you have used your skills to light the person in a 2:1 ratio.)

1. The exposure is made so that the main-lit side of the face is exposed normally. The fill/unlit side of the face falls into place perfectly in relation to the main-lit side, because it was lit to do so by you.

2. The exposure is made so that the fill-lit/unlit side of the face is metered, therefore this side is exposed normally. Because you intended this side of the face to be dark, the shot is overexposed.

3. Because your meter is taking half of its reading from the brighter side, and the other half from the darker side, it thinks that there is less light than there actually is coming from the main light, and therefore will tell you to overexpose your shot.

Change the lighting ratio to 1:1, think through it, and you will see that the problem goes away.

Change the lighting ratio to 4:1, think through it, and you will see that the problem is exacerbated, and you get a pretty poorly exposed shot (one stop over if metered at the camera) that is probably only usable if using negative film and doing some compensation in printing. At 8:1, it is even worse, and you get a very poorly exposed shot (1.5 stops over if metered at the camera), again, salvageable only if using negative film and then doing some print manipulation beyond the norm.

This is why I say that the contrastier the light on the subject, the more important it becomes to meter the main light source instead of the "down the middle" average, which is what you get by pointing the thing at the camera all the time.

CPorter, can you explain this? "Did you say you had a Gossen Luna Pro? Set it to 1/250 at f8 and you'll see there are three stops between the shadowed reading and the sunlight reading." Explain Shadow reading and Sunlight reading please.

2F/2F said:

"To measure incidental light any meter must be...pointed at the camera position."

I keep hearing this repeated everywhere I go. What is the logic behind it? Why would you point an incident meter at the camera if your aim is to measure the light falling on the subject?

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I'm an amateur, but...

The subject is three-dimensional. So some choice has to be made about not just "the light falling on the subject", but the light falling on certain parts of the subject. Sometimes the subject will be lit evenly but that's rare unless you specifically set out to do so (and do it well). If there's a streetlamp reflecting off a newspaper box and illuminating my subject's rear while I'm taking a picture of their face from the bust up, my "incident" reading will be a lot more useful if it takes into account the light falling on the subject that will actually be in the frame.

Is that wrong? I realize that semantically this makes it maybe more a consideration of "reflection", in a sense, but... at a fundamental level reflected light is the only thing that matters, since it's the only thing we see. Or not?

stradibarrius said:

CPorter, can you explain this? "Did you say you had a Gossen Luna Pro? Set it to 1/250 at f8 and you'll see there are three stops between the shadowed reading and the sunlight reading." Explain Shadow reading and Sunlight reading please.

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In your post #25 you said you had a Luna Pro. In my post #29 with my example photos, I gave the exposures for each photo. The shadowed incident reading was at f8 and the sunlit incident reading was at f22, three stops difference.

I was only suggesting that you look at those on your Luna Pro meter.

stradibarrius said:

Because I am doing the photography thing in reverse to many of the folks with lots of experience, starting with digital and moving forward (IMHO) to film I have much more experience with the in camera meter. I am trying to learn to use my hand held more effectively. My old Luna Pro, analogue model, seems to have so much information that I have not taken advantage of yet. Learning to use the incident capability is some of that information. Of all my cameras my RB67 is my favorite and I need to learn to use my hand held effectively with this camera. I shot a roll of film yesterday and exposed each still life scene based on the reflective reading and then the next frame on the incident reading. I am thinking this will teach me something?????

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stradibarrius:

The advantage you have in this situation is that you know the subject you work with quite well. You know how the highlights should appear, and how the shadows appear when the photograph looks best.

This does allow you to work backwards.

The incident meter measures the light itself. Assuming you can get into position to actually read the light that falls on the subject, as long as you point it in the right direction, it will give you useful objective information about the light.

With the exception of some very special circumstances (very dark, or very light subjects mainly), an incident reading will give you the correct exposure.

A meter measuring reflected light will give you a reading influenced by both the light, and the reflectance of the subject. A reflected light reading will need to be interpreted, and most likely adjusted, to be correct.

If you would like to benefit from your earlier experience, you probably need to compare a reading taken with your in-camera digital camera (in manual mode) with the incident and reflected light readings given by your hand meter.

That comparison will give you information about how the meters accept and respond to light (e.g. the angle of acceptance).

Matt

zumbido said:

The subject is three-dimensional. So some choice has to be made about not just "the light falling on the subject", but the light falling on certain parts of the subject. Sometimes the subject will be lit evenly but that's rare unless you specifically set out to do so (and do it well).

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This is definitely part of what I attempted to encompass with my point.

Where the camera lens is has absolutely nothing to do with taking an incident light reading. It is where the light is that matters.

2F/2F said:

This is definitely part of what I attempted to encompass with my point.

Where the camera lens is has absolutely nothing to do with taking an incident light reading. It is where the light is that matters.

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Not quite true.

We usually want to have the bit the camera sees, the bit that will be captured on film, to be exposed the way we want it. Who cares about the parts of the subject we don't see?

So where the camera lens is relative to the subject does indeed matter. It determines what parts of the subject will be on film, which will not.

They don't say those things for nothing, you know.

2F/2F said:

This is definitely part of what I attempted to encompass with my point.

Where the camera lens is has absolutely nothing to do with taking an incident light reading. It is where the light is that matters.

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But wouldn't a corollary be that the light falling on the subject from the direction the camera is viewing is very likely to be the light we want to meter for? Since, after all, that's the light that we'll be viewing the subject in for the photograph.

2F/2F said:

This is definitely part of what I attempted to encompass with my point.

Where the camera lens is has absolutely nothing to do with taking an incident light reading. It is where the light is that matters.

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But wouldn't a corollary be that the light falling on the subject from the direction the camera is viewing is very likely to be the light we want to meter for? Since, after all, that's the light that we'll be viewing the subject in for the photograph.