Incident meter tips?

trondsi · Mar 16, 2016

I shoot mostly slide film, and I recently bought an incident meter. I previously used in-camera meters (with decent, but somewhat variable results).

How do you handle high contrast scenes with incident meters?

For instance, if you are in the shade of some high clouds, but you want to capture a mountaintop which is bathed in sunlight. What would you do?

If contrasts are easy to measure (e.g. in a forest you can just put the meter in light and shade), do you average your measurements?

markbarendt · Mar 16, 2016

With any meter you must understand how the light you are in relates to the scene you want.

The scene you described is easy actually because the mountain is "Sunny 16" if mid day, maybe sunny 11 if early evening.

In this case it's a bit like using a spot meter. Take a reading where you are at and compare that to sunny 16 and you have a reference point for the next time you are in that boat.

Here's a bit more info (there was a url link here which no longer exists)

Poisson Du Jour · Mar 16, 2016

trondsi said:
I shoot mostly slide film, and I recently bought an incident meter. I previously used in-camera meters (with decent, but somewhat variable results).

Single-spot function meters in cameras are only used as a reference point. Relying on the subsequent reading from just one spot can be disastrous, or at least "highly variable". But you can "sweep" the spot meter through the scene and watch the Tv/Av values to get an idea of the brightness range. If you happen to come across an OM4 with its multispot metering and highlight/shadow bias controls, grab it. This was the camera I used back in 1984 to learn how to control exposure using Kodachrome, so once you understand how to apply those controls (spot/hi/lo), subsequent exposure to and practice of spot/multispot metering may be easier to understand.

How do you handle high contrast scenes with incident meters?
*** Measure open area, or close to the prime area of the scene, then memorise this in the meter; next, measure an area in shade, but not deep black. Memorise this also. Then average.

For instance, if you are in the shade of some high clouds, but you want to capture a mountaintop which is bathed in sunlight. What would you do?
*** If you are asking me what I would do, it is use a spot meter if I am to bring home the bacon. The scene you described is one I have confronted many, many times. Neither the brightest (sunlight) nor the darkest (shade) areas should be given priority over either; one measures both, with a mid-tone within the scene as a reference point. Yes! That means you could take along a good old grey (gray) card, but it must be in the same light as the subject.

If contrasts are easy to measure (e.g. in a forest you can just put the meter in light and shade), do you average your measurements?

*** Bright sun and deep shadow wouldn't constitute an easy contrast in my books. Further, if you are using a high contrast slide film e.g. Velvia, don't march it into a high contrast scene — that's not what it's for (switch to Provia 100F). All measurements taken are usually averaged, yes, but some may wish to select just one of the readings as a starting point, and make their own deliberations from there.

Kevin Caulfield · Mar 16, 2016

Unless it's an extreme range between shadow and highlight, you should be able to get a reasonable idea of how to meter the scene, so I agree with Mark.

juan · Mar 16, 2016

Generally with slide film, one is more interested in avoiding highlight blowout than preserving shadow detail. With slide film I always took spot meter readings of a high value and placed it on a high zone. With an incident meter, I'd follow the same concept and meter in the sun. Make a few tests.
Juan

markbarendt · Mar 16, 2016

Poisson Du Jour said:
*** Bright sun and deep shadow wouldn't constitute an easy contrast in my books. Further, if you are using a high contrast slide film e.g. Velvia, don't march it into a high contrast scene — that's not what it's for (switch to Provia 100F). All measurements taken are usually averaged, yes, but some may wish to select just one of the readings as a starting point, and make their own deliberations from there.

Anytime we can easily understand the lighting and what we want the choices become clear and easy. We may not like the options available, but the realities are clear.

wiltw · Mar 16, 2016

High contrast scenes and metering are why spotmeters exist. Incident only tells you 'middle of the brightness range' in the ambient light being measured (shade vs sun) but has no way of knowing a scene is 8EV from min-to-max brightness vs. 14EV from min-to-max brightness. You know only 'middle of the sun illuminated range' and 'middle of the shade illuminated range', but no idea of where 'minimum brightness' falls vs. 'maximum brightness'

That is why, in a studio product photography situation where the dynamic range of the lighting needs to fit within the narrower DR of the offset printed page (e.g. product brochure) after measuring wih incident meter for fundamental exposure I could follow up with spotmeter readings of the brightest and darkest parts of the set and adjust my lighting ratios to suit.

Not limited to studio work, spotmeters have their benefits even in landscape work, which is why practitioners of the Zone System would use them. But incident meter and non-Zone processing is less convoluted and time consuming.

trondsi · Mar 16, 2016

Thanks for the advice folks! Yes, notice that I said that light and dark are "easy to measure" in a forest, not necessarily easy to capture. I use Provia 100f film mostly.

( also: arrgh! So many people talking about spot metering when I just bought an incident meter )

The sunny 16 rule for the bright areas was an interesting thought. My first impulse was maybe "measure in the shade if that's all that you can do, and assume the mountain is 3-4 stops brighter"

wiltw · Mar 16, 2016

trondsi said:
Thanks for the advice folks! Yes, notice that I said that light and dark are "easy to measure" in a forest, not necessarily easy to capture. I use Provia 100f film mostly.

( also: arrgh! So many people talking about spot metering when I just bought an incident meter )

The sunny 16 rule for the bright areas was an interesting thought. My first impulse was maybe "measure in the shade if that's all that you can do, and assume the mountain is 3-4 stops brighter"

Yahbut put me in a wedding location and give me an incident meter and one minute to walk around the church to measure how illumination brightness varies across the scene, and I am set to go and not have to worry about subject brightness wrongly biasing my reflected light measurement! Right tool for the right place, one tool for all places is not 'best'.

markbarendt · Mar 16, 2016

willow said:
Incident only tells you 'middle of the brightness range' in the ambient light being measured (shade vs sun) but has no way of knowing a scene is 8EV from min-to-max brightness vs. 14EV from min-to-max brightness.

Actually it tells you how the film speed point relates to the light falling on the scene or as in the OP's example how open shade relates to the speed point.

In this case the incident meter gives a really good indicator of the luminance range, the difference between the measured reading and sunny 16.

Using an incident meter doesn't mean you don't need to look at the scene or use your head, it means you need to use different clues and math.

willow said:
You know only 'middle of the sun illuminated range' and 'middle of the shade illuminated range', but no idea of where 'minimum brightness' falls vs. 'maximum brightness'

It is true that you can't tie specific reflected tones in the scene to the speed point with the meter. In the OP's case though, the high tones are known. For the slide film that's generally enough.

tedr1 · Mar 16, 2016

sell the incident meter and buy a spot meter

I can recommend the inexpensive Pentax Spotmeter V which uses three commonly available miniature batteries that last forever. This meter is a dream to use, beautifully simple. Check ebay.

Sirius Glass · Mar 16, 2016

tedr1 said:
sell the incident meter and buy a spot meter

Have both. The Gossen Luna Pro SBC is an incident meter and a reflectance meter. Furthermore a spot meter attachment is available. I have one and the spot meter attachment.

markbarendt · Mar 16, 2016

tedr1 said:
sell the incident meter and buy a spot meter

Giggle.

Ok, so you have an opinion.

Can you explain why?

Chan Tran · Mar 16, 2016

wiltw said:
Incident only tells you 'middle of the brightness range' .

The incident meter tells you nothing about the brightness range. It only tells you how much light is falling on the subject.

trondsi · Mar 16, 2016

OK, I know about spot meters, and I have been using the spot meter in my camera. For this thread, let's assume that I want to stretch the incident meter I have as far as it will go, with all sorts of tricks you guys might have up your sleeves.

tedr1 · Mar 16, 2016

this is a reply to MB

You already know how a spot meter works so I won't explain it. I chose a spot meter because it tells the truth (within the limitations of the meter system) about subject brightness range. The photographer uses this information to make choices about contrast and exposure. Nothing complicated really.

Chan Tran · Mar 16, 2016

So you also know that the idea of the incident light meter is that the subject consists of only reflective stuff from 0 to 100% reflection. So it only needs to know how much light is falling on the subject. If the subject emit its own light or only illuminated partially then the incident meter doesn't work.

Sirius Glass · Mar 16, 2016

Chan Tran said:
So you also know that the idea of the incident light meter is that the subject consists of only reflective stuff from 0 to 100% reflection. So it only needs to know how much light is falling on the subject. If the subject emit its own light or only illuminated partially then the incident meter doesn't work.

For example the janitors from Fukushima and Chernobyl who are also known as "Mop and Glo".

trondsi · Mar 16, 2016

OK, my turn to be a bit of a smart ass
The incident meter does not tell you how much light hits the subject, nor necessarily the middle of the light scale. It tells you the middle of the light scale that hits the sphere of the meter. Which is why I thought it wise to be a bit smart about it (e.g. if there's a lot of contrast, and you want to try to catch the middle, so that you retain some detail in both light and shade, maybe let the meter sphere be half illuminated?) But then, I may be overthinking it. Experimentation ensues.

markbarendt · Mar 16, 2016

Chan Tran said:
The incident meter tells you nothing about the brightness range. It only tells you how much light is falling on the subject.

Ok, sure, a single reading with ANY meter tells you nothing about a scene's luminance range. That doesn't mean incident meters can't be used to determine that range. It only means that multiple readings must be taken (just as is necessary with spot meters) and that we have to think a little differently. BTZS is one example here.

If we set the ISO number on the incident meter then the incident meter reading also tells us how that measured value relates to the corresponding film's speed point.

If we know where/what lighting the reading was taken in then that means we can look at the scene and make a very good judgement about where the tones may fall on the film curve.

That judgement call is no different than trying to judge the reflectance of "unknown" targets in the scene. By "unknown" I mean things other than targets with "known" reflectance like a Kodak gray card.

markbarendt · Mar 16, 2016

tedr1 said:
this is a reply to MB

You already know how a spot meter works so I won't explain it. I chose a spot meter because it tells the truth (within the limitations of the meter system) about subject brightness range. The photographer uses this information to make choices about contrast and exposure. Nothing complicated really.

A spot meter can measure exposure in very specific points in the scene but the measured target's reflectance is typically a judgement call, and does not necessarily result in a more true result. Measuring the reflected light from a scene is simply a "more tangible" way of metering, it "feels" emotionally more direct, almost like touching the scene.

Incident meters ask us for a little faith, faith in math and physics, which isn't much of a stretch. We know that a certain amount of incident light will create a certain amount of reflectance off any given subject.

Incident meters can also be used by pointing them directly at the main light source involved, then in a different direction to measure secondary light sources and the difference in the readings can tell us how much contrast differs from normal.

wiltw · Mar 16, 2016

I just took these readings at 10:30am Pacific Daylight Time under a sunny sky...

In sun, incident meter says ISO 400 1/500 f/11 +0.8EV
In shade, incident meter says ISO 400 1/500 f/2.8 +0.1EV
In sun, spotmeter of 18% grey card ('mid-point' target) says 1/500 f/16 +0.0EV
In sun, spotmeter of a black target ays 1/500 f/4 +0.0EV
In shade, spotmeter of 18% grey card ('midpoint' target) says 1/500 f/2.8 +0.3EV
In shade, spotmeter of wet dark soil shows that to be -8.0 relative to measurement #1, or -3.1EV from measurement #2
In sun, spotmeter of sun's reflection on water on off-white fiberglass shows that to be +5.0EV relative to #1

#1 is only 0.2EV different from #3
#2 is only 0.2EV different from #5
The sun lit scene's brightness range is -5.0EV to +5.0EV from the measurement taken in #1
My scene's dynamic range is 13EV, from -8.0EV to +5.0EV from my indicated exposure taken in #1

So #1 indicates BOTH the 'amount of light falling upon the scene' and it also essentially coincides with the 'midpoint tone in the range of black to white' for the portion of the scene which is fully lit by sunlight.

trondsi · Mar 16, 2016

wiltw said:
I just took these readings at 10:30am Pacific Daylight Time under a sunny sky...

In sun, incident meter says ISO 400 1/500 f/11 +0.8EV

In shade, incident meter says ISO 400 1/500 f/2.8 +0.1EV

In sun, spotmeter of 18% grey card ('mid-point' target) says 1/500 f/16 +0.0EV

In sun, spotmeter of a black target ays 1/500 f/4 +0.0EV

In shade, spotmeter of 18% grey card ('midpoint' target) says 1/500 f/2.8 +0.3EV

In shade, spotmeter of wet dark soil shows that to be -8.0 relative to measurement #1, or -3.1EV from measurement #2

In sun, spotmeter of sun's reflection on water on off-white fiberglass shows that to be +5.0EV relative to #1

#1 is only 0.2EV different from #3
#2 is only 0.2EV different from #4
The sun lit scene's brightness range is -5.0EV to +5.0EV from the measurement taken in #1
My scene's dynamic range is 13EV, from -8.0EV to +5.0EV from my indicated exposure taken in #1

So #1 indicates BOTH the 'amount of light falling upon the scene' and it also essentially coincides with the 'midpoint tone in the range of black to white' for the portion of the scene which is fully lit by sunlight.

Did you mean to compare 2 with 5 (instead of 4)?

markbarendt · Mar 16, 2016

trondsi said:
OK, my turn to be a bit of a smart ass
The incident meter does not tell you how much light hits the subject, nor necessarily the middle of the light scale. It tells you the middle of the light scale that hits the sphere of the meter. Which is why I thought it wise to be a bit smart about it (e.g. if there's a lot of contrast, and you want to try to catch the middle, so that you retain some detail in both light and shade, maybe let the meter sphere be half illuminated?) But then, I may be overthinking it. Experimentation ensues.

You are right on track. The dome pointed at the camera typically takes care of that placement nicely but you can, by choice, bias the placement by turning the head.

Another option here is duplexing, retract the dome and measure highlight exposure by pointing directly at the main light source (this protects the highlights) then measure the exposure the camera will see by pointing the meter head at the camera (this protects the mid tones), average the readings and you will normally have a very workable exposure setting for slide film. Since negative film almost always has more latitude than slides this is also a very workable technique for negatives. You can choose your priorities as you please though, if you want to have lots of shadow detail orient the head to bias the reading that way.

markbarendt · Mar 16, 2016

wiltw said:
So #1 indicates BOTH the 'amount of light falling upon the scene' and it also essentially coincides with the 'midpoint tone in the range of black to white' for the portion of the scene which is fully lit by sunlight.

It needs to be understood that the meter shows us a relationship between the measured luminance the meter sees and the film speed point (true on both types). Exposure determines where the shadows fall on the film curve. Film development determines at which density point the mid and high tones fall.

The mid point is a variable. As an example if you push a film the gray card point will fall as a lighter tone in the positive, if you pull a film the gray card will fall darker in the positive.

Incident meter tips?

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