Help me figure out what's wrong with my light meter?
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Your intent is well understood; I believe you meant C250 and C330.
Yes I meant C250 and C330.
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@dcy on those tricky lighting scenarios: try a shot on the Digital camera using the recommended settings from the Luna-Pro F as an exercise. You’ll see what it was trying to do. Plus you’ll get better at recognizing what you like when it comes to tricky lighting.
Next try some sunsets, and backlit lanscapes. Those are the scenes that make me throw my hands up. I can’t figure them out without a spotmeter. And even then I’m not sure.
Next try some sunsets, and backlit lanscapes. Those are the scenes that make me throw my hands up. I can’t figure them out without a spotmeter. And even then I’m not sure.
MattKing
Moderator
This is a really good idea.
In essence, it turns the question around.
Instead of asking "how do I test my meter?" it asks "what will the results of using my meter cause my photos to look like?".
When we suggest using film to test equipment out, this is essentially what we are suggesting.
OP
OP
Well... it was trying to expose the tree correctly at the expense of the rest of the scene, was it not?
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It was ignoring the bright light behind the tree which isn't part of the picture.
There is a book called Beyond the Zone System (often abbreviated here BTZS) where Phil Davis explains how to use an incident meter in a way that considers subject light range.
Here he's showing a mistake of reading light that's too far in the shade.
Yes!
It depends...if the Gossen meter was exactly as illustrated in the photo posted in #118, its hemisphere is IN THE SUN and therefore it would expose the shadow areas -3EV from the indicated exposure. It would only expose 'for the tree' (or any mid-tones) if the hemisphere was located fully *in the shadow area*.
The reflected light meter would 'see' both areas, and likely exposed for somewhere 'in the middle' between the bright and the shadow areas, biasing toward one or the other depending upon matrix metering metering zones or any intelligent biasing (like putting more weight on the less-bright zones) or other forms of weighting.
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OP
OP
Fair question. No, it wasn't exactly as illustrated in the photo. When I took the reading I put the meter just a couple inches from the tree trunk, but I had to move a to take a photo of the meter because the tree was in the way. In that shot, the meter is about 2 feett away from where I took the reading. I guess I could have hugged the tree so the meter would be in the right place, but I didn't think of that.
Yeah. The incident meter is sampling just one spot (presumably the subject) while the reflected light meter can't avoid being pulled toward shorter exposures by the bright background.
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You used the Gossen correctly.
Evaluative (ESP) metering is different than weighted average. It runs a matrix of readings through a library of stored pictures. It CAN avoid being pulled towards shorter exposures by the bright background. It will try to throw out bright readings that are not important if it sees the pattern (like a sliver of sky)
MattKing
Moderator
A small point, but it can be important.
Your Gossen meter is similar to most of our meters when used in incident mode - it employs an integrating "dome" over the sensor.
As such, the incident light that is measured is integrated from all directions - e.g. the sun, the open sky, the reflections off nearby surfaces - everything that may serve to illuminate the subject. The directionality of that light is "integral" (pun sort of intended) in how the subject is modeled in the resulting photograph.
That integrating function is the reason that, when you are using the meter in incident mode, that you place the meter near the part of the subject facing toward the camera and point the meter at the camera - not at the light source.
Some incident meters offer a choice. If you are using them for general photography, employ the integrating dome and point them toward the camera. If you are using them for photographing artwork or documents or something similar, use them with a flat diffuser and point them at the light source(s).
D, Matt describes very well the 'intergrated' aspect of incident light.
Your description only applies to the very simplest method of pointing a reflected meter in a random direction.
Experienced user knows what/how to point the meter. Once again...it's not an 'auto-exposure' device but a tool that's only as accurate or sophisticated as it's user....
For situations like the shaded tree and brightly lit background, there is an advanced technique of incident metering called DUPLEX METERING. Dunn describes it in his 1950’s era book. Chris Crawford provides a really nice description of that prioress:
Although Crawford stated that a flat diffuser is required, a hemispheric dome also works. Dunn writes of many meter for this technique, all having hemispheric domes or the equivalent.
Although Crawford stated that a flat diffuser is required, a hemispheric dome also works. Dunn writes of many meter for this technique, all having hemispheric domes or the equivalent.
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To put is precisely: The incident meter NEVER 'samples the subject', it samples the LIGHT STRIKING the AREA in which the hemisphere is located ) and if the subject is within light similar to that area, the subject brightness will fall wherever within the range of brightnessesn it inherent falls withing. That is, if the subject is darker than 'midtone' by -2EV, it will be exposed so that it falls at -2EV relative to any midtones in that same light. An incident meter will never be influenced by the brightness of anything around because it never sees that brightness (unless the hemisphere falls into light area of same brightness)...it see LIGHT falling on the hemisphere...it sees no 'subject'
(The preceding description is somewhat simplified (to base principle), as the description does not factor that angle at which the hemisphere is aimed, when it is (correctly) aimed at the location of the lens shooting the scene. -- which influences the measurement)
Back to your metering situation...so it so, which is as if your hemisphere was indeed located in 'light as same brightness as the subject tree was located in (shade)', in which case the exposure made was indeed 'for the subject'.
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That is why I asked the OP to test the meter under sunny 16 condition in incident mode because the sunny 16 is stated based on the light falling on the earth and not the reflectance of any subject.
IF you use a digital camera as a meter, you can check the histogram and blinkies for clipping and for general appearance of the picture in the screen.
OP
OP
Yay!
That's really interesting! I didn't know that.
Yeah. Even that will be imperfect. Ideally what you really want to know is how the light falling on the subject translates into light reaching the camera. Pointing the orb toward the camera is the least biased way to orient the orb, but it wont' be perfect. The subject has its own texture and color so what gets sent to the camera won't exactly match what gets diffused into a white orb. Presumably that's the problem that spot meters fix.
Interesting. I hadn't heard of meters with flat diffusers.
OP
OP
Well, it describes the specific method that I was using. I was trying to describe what actually happened when the meter values were recorded.
I could have, for example, pointed the camera in a different direction with more uniform lighting that, in my judgement, matched the lighting on tree trunk. But that was not what Bill instructed me to do, and it would open up the question of whether I correctly judged the lighting.
Yes. That is why I am attentively reading the advice from you guys. I also set aside the books that I have that cover light meters. I've read some of what they say about light meters, but I'm not yet done reading all they have to say.
It's time mate, reading needs to go with practicing
. Loading film into your beloved camera and head down the town. Try your best to remember where you point your handheld light meter whenever you use it for which frame. Everybody will have their own technicque with the device they are holding. After years of fixing and calibrating handheld light meter, I learn alot from my customers. But they are nothing if I don't practice.
MattKing
Moderator
If you know about the light that hits the subject, and can see the subject, you know about the light that will reach the camera - thanks to those eyes.
Because cameras - both digital and film - and film itself are essentially designed to emulate those very eyes, and the vision system we use those eyes with.
Except in the case of purely abstract subjects, if we know how much light is incident on the subject, we know how to set the camera in order to record the subject accurately, as it appears in real life.
Sometimes, with very dark and/or very light subjects, it is a good idea to intentionally increase or decrease the exposure, in order to make sure that the subject details are recorded by the film within that part of its characteristic curve that is best able to record them. But usually, if you follow the incident meter's recommendation, you will be happy with the result.
The other exception is when there is really complex lighting - often multiple sources involved.
The main reason you probably have less familiarity with incident light meters is that they can't be used as in-camera meters, and in modern times we expect to rely on in-camera meters to fulfil our exposure setting needs.
The other disadvantage of incident light metering is that sometimes you have difficulty getting the meter where it needs to be in order to measure the light incident on the subject - think photos from long distances, for example.
But in reality, an in-camera meter, or in fact any reflected light meter, will always need to rely on what are essentially assumptions in order to provide an answer to how much light is illuminating the subject, and therefore how much exposure should be set on the camera.
Yay!
That's really interesting! I didn't know that.
Yeah. Even that will be imperfect. Ideally what you really want to know is how the light falling on the subject translates into light reaching the camera. Pointing the orb toward the camera is the least biased way to orient the orb, but it wont' be perfect. The subject has its own texture and color so what gets sent to the camera won't exactly match what gets diffused into a white orb. Presumably that's the problem that spot meters fix.
Interesting. I hadn't heard of meters with flat diffusers.
As an example, the Sekonic L398a comes with a sphere (Lumisphere), a flat diffuser disk (Lumidisc), and an attachment with a grid (Lumigrid) of holes in it. They desscribe their use like this:
Lumisphere: Incident Light Measurement. From position where subject is to be measured, point Lumisphere in direction of camera.
Lumidisc: For illumination contrast adjustment and illuminance measurement. Hold meter at subject position and point lumidisc at main light. Repeat for fill light. Calculate contrast ratio by comparing footcandle readings. Can also be used for reading illuminance (lux) reading in footcandles.
Lumigrid: Reflected Light Measurement. Point lumigrid directly toward part of subject to be measured. In case of measuring narrow areas, as close as possible to the subject, measure reflected light from main point of subject.
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