Confusion between incident meters and in-built spot metering

Not sure if this should be in 'Lighting' but here goes...

I've just read two books about the Zone System, and they have really helped me understand what has been a mystery to me for some time now, but I'm confused about one small area that I hope someone can help me with - metering.

I now understand that one should previsualise the darkest area of the scene for which he wishes some small aspect of detail or texture to be viewable in the finished print and expose for that. By expose, I mean meter that area until a Zone V (18% grey) reading is indicated, and then stop down (-) two stops to Zone III. Press shutter.

The bit I am confused about is the difference between metering that particular part of the scene using the cameras in-built spot meter, or a Sekonic incident light meter.

As I understand things, the cameras in-built meter bases the reading on the reflectance of that dark area (using spot). So, if it's a black suit, for example, the camera reads it and provides a meter reading to give an exposure based on what it thinks is 18% grey and the photographer then stops down a couple to make sure it's black.

But with an incident light meter, it reads the light falling on that particular area of the scene and ignores the fact that the dark area of the scene is a black suit or a white dress. The pure reading of the light is given. I understand that.

My question ultimately then is this : to ensure that dark area of the scene is placed in Zone III, with the incident light meter, is that reading also an 18% grey average reading, and if so, I assume that I still stop down to Zone III on my camera (having dialled in what the incident light meter tells me) to get my darkest shadow?

As an example, man with a black suit and woman in a white dress sat on a bench. It overcast and no direct light, so average contrast. Darkest shadow is the mans black suit, and everything darker can go into total black. Camera in-built spot meter says suit is F5.6 @ 1/60th, so stop down to 1/125th to ensure it's black.

So would the Incident light meter also say F5.6 @ 1/60th for the same area? I assume not, as it's not basing the reading on reflectance, but then again, it is giving a reading based on giving what it thinks is a "correct" exposure (which I assume is also 18% grey for incident meters), not a Zone III shadow. So would I stop down the camera, or not? I'm confused!?

Any clarification appreciated

Ta

Ted

ted_smith said:

My question ultimately then is this : to ensure that dark area of the scene is placed in Zone III, with the incident light meter, is that reading also an 18% grey average reading, and if so, I assume that I still stop down to Zone III on my camera (having dialled in what the incident light meter tells me) to get my darkest shadow?

As an example, man with a black suit and woman in a white dress sat on a bench. It overcast and no direct light, so average contrast. Darkest shadow is the mans black suit, and everything darker can go into total black. Camera in-built spot meter says suit is F5.6 @ 1/60th, so stop down to 1/15th to ensure it's black.

So would the Incident light meter also say F5.6 @ 1/60th for the same area? I assume not, as it's not basing the reading on reflectance, but then again, it is giving a reading based on giving what it thinks is a "correct" exposure (which I assume is also 18% grey for incident meters), not a Zone III shadow. So would I stop down the camera, or not? I'm confused!?

Any clarification appreciated

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You do what the incident meter says you should do, without any correction.

An incident light meter does not meter for a specific area, other than the entire area the light it is metering falls on. No matter what different tones there are in that area.
So an incident light meter does not, cannot, produce different readings for black bits and white bits in the scene.
And that's a very good thing too!

Think about it the dark suit will appear dark, because it reflects less of the light that falls on it, the white dress appears light because it reflects lots of the light that falls on it. You don't have to do anything for that to happen. The tone of the suit and dress will do that all by themselves.
But a spot meter sees dark things and light things, and doesn't know that this is because these things actually differ in tone. Stupid things, reflected light meters.

All you have to know is is how much light there is for each to reflect in their peculiar way, i.e. get an incident light reading.
Base the camera setting on that, and everything will be good automatically.

My question ultimately then is this : to ensure that dark area of the scene is placed in Zone III, with the incident light meter, is that reading also an 18% grey average reading, and if so, I assume that I still stop down to Zone III on my camera (having dialled in what the incident light meter tells me) to get my darkest shadow?

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No. As stated above, incident light meters have no idea about subject brightness. With an incident light meter you measure the light, and that's that.

What you are trying to do--ensure that a certain dark object will render on the film--is impossible to do with an incident light meter. You have to meter the dark object with a reflective light meter to see just how dark it is. If you need to do this, an incident meter is not the right tool for you.

Now, when I use an incident light meter, and notice that there is a particular bit of darkness that I want rendered on the film, I'm free to expose a bit extra than the light meter reading if I want. But I'm back to guessing as to just how much extra to expose.

Q.G. said:

All you have to know is is how much light there is for each to reflect in their peculiar way, i.e. get an incident light reading.
Base the camera setting on that, and everything will be good automatically.

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Everything will be pretty good automatically if the light is even and the contrast range is not too great. If the light falling on the scene is not even, an incident meter can mislead the inexperienced just as badly as a reflected meter can.

And if you enjoy mucking around with the zone system, you will have more fun with a reflected meter!

Ian

Look, an incident meter will always give you a better reading than any sort of reflected meter. I don't care if it's a spot meter, full average, center weighted average, matrix, what have you. They just work. Sometimes it's not logistically practical or even possible to use one; but when you can, an incident reading is always spot on. If the subject is very dark, then open up a stop to keep all the tones from bunching up at the bottom of the curve. If the subject is very light, close down a stop to keep the same thing from happening at the top of the curve. It's really very simple. Might you be getting confused as to how to operate an incident meter? The dome gets pointed at the camera from the subject position when the reading is made. You do not point the dome at the subject. Don't laugh and don't excoriate me for assuming a mistake. I've seen "experienced" photographers do just that, then exclaim loudly that their incident meter is a piece of crap.

Frank - I use an incident meter often, and they are fantastic things, but if they were "always spot on" it would not be necessary to correct for:
- uneven light
- great contrast range
- subject very dark
- subject very light
- situations where they are not practical
- etc
When you state that they are simple and always accurate, you are basing that on your acquired experience of when corrections need to be made. The truth is that, in many situations an incident meter is the easiest thing to use. But in some situations, a reflected meter is the better tool for the job.

Ian

fschifano said:

Look, an incident meter will always give you a better reading than any sort of reflected meter. I don't care if it's a spot meter, full average, center weighted average, matrix, what have you. They just work. Sometimes it's not logistically practical or even possible to use one; but when you can, an incident reading is always spot on. If the subject is very dark, then open up a stop to keep all the tones from bunching up at the bottom of the curve. If the subject is very light, close down a stop to keep the same thing from happening at the top of the curve. It's really very simple. Might you be getting confused as to how to operate an incident meter? The dome gets pointed at the camera from the subject position when the reading is made. You do not point the dome at the subject. Don't laugh and don't excoriate me for assuming a mistake. I've seen "experienced" photographers do just that, then exclaim loudly that their incident meter is a piece of crap.

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I am waiting for a Gossen Luna Lux light meter that I just ordered to come. Therefore I was reading the manual on line when this thread was posted.

I have always used a reflected meter. After reading AA and BTZS many times, Roger Hicks posts here, Ralph Lambrecht, 2F/2F and others, I learned to select what I want to be neutral gray [grey, 18%, or the infamous 12%] for several spot readings [for example, when the SBR is 12 stops] after taking an average reading [to get a sense]. Most of the time the weighted readings of the Nikons and Hasselblads are accurate enough.

Now reading the Gossen Luna Lux light meter manual, I get the sense that what I am doing is the essence of Zone and BTZS without the development pushing or pulling. Further the discussion in the manual sheds more light, pun intended, on the incident metering.

Since, for the first time, I will have a incident meter to refer to while I am determining the exposure.

Ralph Lambrecht's second edition will help.

But the one constant I have always seen is that the Zone versus BTZS versus Reflected versus Incidence take on a religious war tone after while. I hope the the Messianic attitudes are left out of this thread so that others and myself can gain the most information from this thread.

Steve

As Frank states, the incident meter is the simplest, and in most cases, the most reliable way of reading for general exposure.

One reason for using spot (reflectance) metering is if you have enough experience to know that you need additional information to make the exposure for image you want, such as:
You know the range is too great for the film/dev combo you are using and you need to quantify the full range of values in the subject, then "place" values at the right levels to yield a good negative after development.
Or the opposite case of a flat subject, it's nice to know what you are establishing as the bottom end with detail (III), then see what the brightest area is to help determine the amount of additional development you need to achieve the range you want in the neg.
Or the lighting on the subject is very uneven (in the woods, etc) and you just want to know what the whole range is in terms of reflected values.

But, as you might infer from Frank's post, it's much easier to stay out of trouble with an incident meter. I have a great old Sekonic Studio L-398, which I usually have with me, but I confess don't use as often as I should.

Fred Pickers old Zone VI Workshop, copyright 1974 is a great reference, his explanations are direct and conversational. I used to use this as a text in a college level course back in the 70's and it was often complimented by students as a great reference. He gives simple exercises to do that show you by experience. You might find copies on e..y, don't know.
There is also a forum on exposure you might check out on the Apug site.

Hmm - I wonder if, in the uneven lighting case, there is a method of taking several readings with the incident meter and deducing exposure by incident "zones" based on incident light. I didn't think that through, just had the thought on my second glass of pinot grisio...

Uneven lighting is easy to handle with an incident meter too. Take two readings, one in the shade and one in the light, then average them out. Weight the averages in favor of where you want your tones to be and develop accordingly. Like everything else it takes a little experience and practice, but it's not rocket science. If you have a subject that's partly in shade and partly in light, the shaded portion will meter between 1/2 and two stops under the lighted part every time in daylight - depending upon how deep the shade is. After a while, you just know.

I too have a very old Sekonic L-398. It's not very sensitive and so isn't great in very low light situations, but man that thing is spot on after all these years.

Incident meters do not meter for tonal placement, as reflected light meters do. They meter an amount of light illuminating an area, not the lightness of darkness of an object itself. They inform you of a level of light that exists at your location, not how bright or dark your subject is. They measure light, not objects.

So, if you want to perform precise tonal placement, incident meters are not for you.

However, you may find that you really don't need to perform precise tonal placement to get the results you need. I sure have. I used to use nothing but a spot meter. However, when a free incident meter came my way, I picked up the habit of using it in hand held street/travel photography. I soon found that the meter had many advantages over the spot meter (quick, direct reading being #1, very important in every type of shooting I do except for studio still life pix). I found that with some ability and experience and an eye for light and contrast, it could be used to get results that are near identical enough to make me switch to incident meters for almost everything.

I often have my spot meter on me, but I use it pretty rarely, unless I really have time (i.e. I am using a tripod and the light is fairly static). Now I use the spot meter more for measuring subject brightness range than for actually deciding exposure. I still tweak exposure and development when using an incident meter, based on how I think the range of tones within the composition will jive with my Oriental VC or Emaks paper.

What really swayed this decision to relegate the spot meter to "second meter" status was the recorded, tested-for fact that almost never do the exposure and development I use with an incident meter, and those I use with a spot meter on the same picture vary by more than 1/2 stop in exposure or half grade of contrast.

In the end, I feel somewhat the opposite of most people. They probably feel that incident meters are better for more casual shooters who just want a decent exposure quickly, and never alter the contrast of their negatives, and spot meters are for the real pros who know what they are doing on a technical level, and try to get every shot perfect on the negative.

The way I feel about it is that spot meters are a good way to help someone who doesn't have a developed eye for light and contrast. I feel that they are good tools for those beginners who are just beginning to understand how to use exposure and development to control their negatives, but don't yet know when they might need to alter these things by simply looking at a scene in front of them and seeing the light. However, the way I see it, as one develops a better and better sense of these things, the spot meter becomes more and more of a hindrance to normal, every day photography, and an incident meter combined with an eye can give you results that are within half a stop and half a grade, both well within the range that is easily controlled in printing, using either VC or graded papers. This is not to take anything away from those who really do "see" light and luminance range, yet still use them. Just saying that I believe that only beginners learning to see light really need them.

If you have the time, add a spot meter on top to measure luminance range, and you eliminate that half stop/grade, but still meter for the midtone. It is the best of both worlds, IMHO. I get to meter for a midtone and control highlights and shadows around it, rather than having a shadow placement determine everything about the exposure and development. The format makes more sense to me, and leads to more consistent mid tones IME. I feel that the mid tones are the most important part of any image to control, a very incident meter way to look at it. the spot meter way to look at it would be that the detail in the high and low tones are the most important part of any image. The way I like to think of it is as a see saw with middle grey at the fulcrum, with black and white riding the see saw on opposite sides, versus a kite, with the flyer of the kite being the low tones, the kite being the high tones, and the kite string being the mid tones. The see saw is the incident meter, and the kite is the reflected (spot) meter.

Re the points that Frank and 2F/2F make - I remember at one point later in his time, Fred Picker began to recommend, with 35mm, at least, just metering for highlights, add 2-3 stops, depending.. This kept the range in check, and with small neg quality, maybe the difference in print quality at the low end wasn't worth worrying about.
As I use the new, better VC papers, with split grade printing, I'm not sure that elaborate spot reading (zonal placement) is of much benefit, any size format. As long as you don't have a part of the image at the extreme end of the normal range, it may make more sense to make a good general exposure. Sometimes, if I'm in a hurry, I even just use the Sunny 16 rule.

An incident meter reads how much light is falling on your your subject and gives you the camera setting. Think of it as placing Zone V.

In practice simply press the incident meter gently to the tip of your subjects nose, aim the meter's dome at camera, push the button, then set the camera exactly as the meter suggests; no offsets or corrections. Used in this manner it is nearly foolproof for getting a great exposure of your primary subject.

The black suit will "fall" where it needs to, the white dress will "fall" where it needs to, faces will fall where they need to; all automatically.

Only when using a spot or camera meter do you need to "zone".

markbarendt said:

The black suit will "fall" where it needs to, the white dress will "fall" where it needs to, faces will fall where they need to; all automatically.

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For the mid tones, yes. However, the blacks and whites will happen only if the range of the scene matches the range of your film matches the range of your paper. Otherwise, adjustment is necessary. You still need to see light and range to make incident meters work with great control. IMHO, and as I stated in my previous post, seeing these things and using an incident meter is generally better than using a spot meter.

2F/2F,

I do agree that seeing the contrast and adjusting is needed, the question for me is more of when & where.

Shooting mostly roll film, and sadly more than one SBR per roll, I use a standard development routine and adjust contrast at the print rather than in film development.

Many thanks to all of you - I think you have all cummulatively answered my question. I am extremely appreciative of the time and effort several of you have invested in your replies.

Ted

I'm a pragmasist when it comes to meters

I use both types of meters. I use incident meter when the
lighting is even. I admit I mostly use relfected metering when I shoot. The reflected meter will however, allow me previsualize the value of an area. Reflected meters will also give me infomation on how to fit a scene with a wide range of luminosity within the films dynamic range. When you need a hammer use a hammer. When you need to use a screwdriver use a screwdriver.

Ted:

I had to chuckle when I read your first post in the thread .

One of your first phrases was:

"I'm confused about one small area that I hope someone can help me with - metering." (my emphasis added!)

As you most likely realize from the plethora of responses here and in other threads, metering itself is both science and art, and is not a small area at all.

FWIW, I'm a proponent of incident metering, but still make use of in camera and other reflected light meters on a regular basis.

I regularly say to myself something like: "how many stops extra (or less) light is the metered area reflecting as compared to a grey card". You can train your meter, eye and mind to make that determination quite accurately - all it takes is a bit of practice.