incident vs. reflective metering

[jmr237]

Advertisement (gone after registration)

Hopefully this is the right place for this question.

 

I have been thinking about this in light of the release of the new M-A meterless film camera.

 

Here are my questions:

 

What are the advantages of an incident meter vs. an in-camera reflective meter?

When would one of these metering approaches be preferred over the other?

All else being equal, is incident metering preferred? See this tutorial in favor of incident metering.

 

I understand the technical difference between the two metering types: incident metering measures the light that falls on a subject, and reflective metering measures the light that the subject reflects into the camera. But I don't understand why you would use one approach over the other.

 

I'm interested in this from a learning perspective, but also from the perspective of how it could inform one's camera choice (e.g. an M-A or M3 vs. a camera with a meter such as an M6 or MP).

[IkarusJohn]

People far more knowledgeable and far more clever than me will jump in shortly, but here's my reasoning.

 

Incident light metering simply gives you an EV value - many old style cameras (Hasselblad 500 series for one) would then let you set that EV value on your lens barrel giving you the right combination of shutter and aperture for the incident light. That meant that blacks were black, and whites were white, as God intended them.

 

To get a reading, you just held your light meter in front of your subject, with the sensor facing the camera. The downside to this approach is if you can't get the light meter in the same light as your subject (say you're in the shade of a building or something like that). Then you'd need to consider taking a reflective reading off your subject.

 

Things get tricky with reflective readings because the light meter will assume that what you are reading is a standard reflective value of 18% grey. So, if you're in snow, the light meter will significantly under expose as it tries to bring the bright scene down to that standard neutral shade. Similarly, in dark scenes, the meter will try to over expose. This doesn't happen with an incident reading for obvious reasons, but it does for spot and centre weighted meters. So, you find yourself using centre weighting and shooting manual, then adjusting for these misleading readings your meter is giving you, or spot metering and setting the spot on a skin tone which best approximates 18% neutral grey (or you stick a grey card in the image and meter off that).

 

The only other alternative is to use a more complex spot meter (like a Gossen spot meter), which measures exactly a 1 degree spot using the zone system (described in detail in Ansel Adams' excellent book "The Camera") - the meter then works out what is white (zone 10), what is black (zone 0) and what is middle grey (zone 5). While very old fashioned, this is actually incredibly useful and remarkably accurate once you get the hang of it (I think the Hasselblad digitals use this system).

 

For me, I'm just a bit lazy, and will often just use sunny 16. I also have a not bad meter app in my iPhone.

 

Hope this helps

John

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[jmr237]

Thanks for the thoughts. I have read Adams' three books (Camera/Negative/Print) and I understand the theory of the zone system.

 

Are you saying that the incident meter provides a reading that will register the subject relative to its zone, whereas the reflective meter is providing a reading that will put the subject in zone V?

[IkarusJohn]

Are you saying that the incident meter provides a reading that will register the subject relative to its zone, whereas the reflective meter is providing a reading that will put the subject in zone V?

 

No, the Zone system is relevant only to reflective readings. Incident readings simply tell you the intensity of the light falling on the meter, which will hopefully be the same as falls on the subject. If your camera is set to the exposure appropriate for the incident light, then all zones should (roughly) be exposed correctly.

 

Put another way, if you expose for the ambient light (incident reading), then you don't need to worry about the zones and all surfaces will reflect the light according to the intensity of the ambient light.

 

In short, if you get the incident light reading right, your exposure value will be the same regardless of the reflectivity of your subject. Conversely, if you're reading a reflection, the meter needs to know what zone the reflective surface falls into - you need to tell it if it's white, black or somewhere in between - otherwise the camera will assume its 18% grey.

 

Has that helped?

[sblitz]

Thanks John -- It would seem to me then that if you have a spot reflective meter and point it at face you would have the same reading as if you did the same using an incident meter? I tend to use sunny 16 when outside, or at least take a couple of readings against the sidewalk and then just adjust from there, 2 stops for light shade another 2 for much darker shade. Funny but I end up being faster using my M4 simply because once set I focus on the subject making quick adjustments whereas with the M6 I am always fiddling to get the arrows in line. Yes, I know I could do the same as with the M4 but somehow between the ears it doesn't work that way ...... thanks for answers above, much appreciated.

[Bill Clark]

My thinking, as I type this little ditty. Latitude with film, especially with black & white. Latitude with RAW capture.

 

However, I see pluses and minuses with each method of measuring light.

 

What do I do? I tend to rely, perhaps too much, on the latitude. However, I work at getting exposure correct during the capture stage.

 

I work on getting balance. If I make photos with a variance of light in a scene, I work at getting balance. I'm talking on people photography. If the background is one setting, people at another, I work to get, if anything, balance or the background just a wee bit under exposed. I can use HDR for scenic photography.

 

I dislike to have a group with decent exposure and the background blown out. Or a nice blue sky is now white. I don't like that.

 

I do use the histogram with digital as my light meter. If I use film I can use my digital camera to get proper exposure, kind of like using a Polaroid back in the olden days.

[Jeff S]

Advertisement (gone after registration)

Lars articulated the differences well in this FAQ.

 

Jeff

[giordano]

Something that should be mentioned in this thread is the old saying "Expose for the shadows, develop for the highlights", out of which Adams formalised the Zone system. Metering the shadows is most conveniently done with a reflected light meter.

 

But "expose for the shadows" and Zone system only apply to still monochrome negative/positive processes. There, they are technically superior because they take advantage of - even manipulate - the shapes of the characteristic curves of film and printing paper emulsions to "map" the tonal range of the subject onto the tonal range of the paper.

 

Elsewhere - i.e. colour negative, colour reversal, monochrome reversal, digital and moving images* - the most satisfactory results are generally achieved if the non-specular highlights are not (quite) burnt out, in which case the mid tones will be correctly placed on the curve (and the shadows will have to look after themselves unless you supply auxiliary light). And that is exactly what an incident meter is designed to do.

 

*For slightly different reasons in each case.

[Stealth3kpl]

This question of reflective vs incident is why I don't put too much stock in people insisting they "use Tri-X @ 320".

Are they really??

Pete

[spydrxx]

Early in my photography journey I loved the results (color slides) from incident metering, particularly as they, for me, tended to result in consistently excellent results. Later, I began experimenting with reflective metering, which I think requires quite a bit more thought. By the time I finally came to terms with the differences and nuances of each, matrix metering had advanced so well that I often relied on it almost exclusively in my cameras which had it. Now I've come full circle and feel comfortable with whatever is tossed my direction. In daylight I'm happy with Sunny 16 estimates, as a substitute for incident metering. About once each year I run a test roll...beginning with sunny 16, then take an incident reading, then reflected readings and reconcile the differences. When all is said and done, if I had to choose between incident and reflective metering...I'd go for incident except in very unusual circumstances involving very high contrast subjects in contrasty lighting. If you understand the nuances of the differences, I don't think it really matters much which you use as long as you can get your meter where it needs to be.

[IkarusJohn]

Thanks John -- It would seem to me then that if you have a spot reflective meter and point it at face you would have the same reading as if you did the same using an incident meter?

 

I think that still raises problems - if you're comfortable that face roughly corresponds to 18% grey (African faces? faces in shadow?), then yes. I have found that a very unreliable approach myself ...

 

When the Monochrom came out, I was very interested int he ETTR approach. My background is really in slides, and my biggest bugbear is blown highlights, so my tendency has always been to slightly under-expose. With Kodachrome, under-exposing tended to give stronger colours.

 

I often wonder if people get a bit too excited about exposure. Granted, digital is a little more intolerant, but if you're pretty much right the bigger issue is to look at the scene and decide where blow-outs will occur and what will affect you overall reading - lots of bright light? or lots of deep shadows? If you use reflective metering a lot, you can get very tied up in what you're metering, and playing with exposure compensation buttons, none of which is very productive.

 

Conversely, if you understand that it is the light falling on your subject which determines your exposure setting (and adjust accordingly) the complexities of the technology fall away and you become far more focusing on the balance of your picture.

 

Other's experience will obviously vary.

 

Cheers

John

[jmr237]

Thanks John and others for your time and thoughts. Let me see if I can get this right:

 

Let's say that I am taking a picture of someone in even light. If I use my M6's center-weighted meter and meter for the subject's face, the meter will expose the subject's face to be middle 18% grey (Zone V). I am measuring the light that reflects from the subject's face into the camera.

 

If I hold an incident meter in front of the subject's face, and point it toward my camera, it will measure the exposure value of the light that falls onto the subject's face.

 

All of that makes sense. Here's the part I don't get:

 

How does the incident meter translate that exposure value into a setting of ISO, shutter speed, and aperture? And doesn't that translation require placing that exposure on a zone?

[IkarusJohn]

Here's the part I don't get:

 

 

 

How does the incident meter translate that exposure value into a setting of ISO, shutter speed, and aperture? And doesn't that translation require placing that exposure on a zone?

 

 

With the incident meter, you set the ISO (and also reflective), and you then get an EV value. That sets the ideal combination of shutter and aperture. You don't need a zone as such as the meter is reading light intensity. So, theoretically, your various zones will be whites, blacks and greys as your meter reads the light hitting them rather than what they reflect.

 

The only setting you need for incident reading is ISO as this sets the sensitivity of the film/sensor. Not sure I'm explaining that right. Does it help?

[tobey bilek]

Pure foolishness not to use a meter unless you always have standard conditions, ie studio or summer sun in same latitude. Although it would be embarrassing to find your flash was set wrong after a paid gig.

 

There be 3 kinds of meters, incident, reflective, & spot. In camera and Weston Master Series are both reflective.

 

Incident is wonderful for average scenes or studio work where the meter can see/measure the light falling on subject. It can not tell you if parts are too light or dark to be captured correctly.

 

Reflected readings need to be corrected for light or dark subject colors because it wants to make everything grey. It does not know if it is looking at a very bright scene or a mountain with snow on it. The exposures are 1.5 to 2 stops different.

 

Spot meters are a subset of reflected meters and deserve special treatment. They can be used to measure the brightest area and darkest areas to see if they will be captured correctly. Expose accordingly. With experience you can measure clouds, spring grass, summer grass different types of tree bark, sand etc and know the compensation so they are rendered properly and not grey. The Pentax meters have an IRE, institute of radio engineers, scale to help properly place the different colors.

[giordano]

Let's say that I am taking a picture of someone in even light. If I use my M6's center-weighted meter and meter for the subject's face, the meter will expose the subject's face to be middle 18% grey (Zone V). I am measuring the light that reflects from the subject's face into the camera.

 

Yes - and the face will be placed in zone V regardless of skin tone. A very dark Papuan complexion will be rendered in the same grey as a very pale Finnish one.

 

If I hold an incident meter in front of the subject's face, and point it toward my camera, it will measure the exposure value of the light that falls onto the subject's face.

 

No. An exposure value is a just a combination of f/ stop and exposure time, or rather the combinations (e.g. 1/500 at f/1.4, 1/250 at f/2, 1/125 at f/2.8...) that amount to the same amount of light on the film in any given scene lighting. An incident meter measures the light, factors in the ISO, and gives you the exposure (whether as an EV number or a range of shutter/aperture combinations).

 

How does the incident meter translate that exposure value into a setting of ISO, shutter speed, and aperture? And doesn't that translation require placing that exposure on a zone?

 

The Zone system is a formal method of optimising exposure by matching the range of tones in the scene to the range of tones that the film can deliver. This is irrelevant to an incident meter because it doesn't see the scene but the light falling it, as integrated by the dome over its sensor. There is simply no formal point of contact between incident readings and the zone system.

 

In practice, however, given a simple scene with front lighting, reflected and incident meters should indicate the same exposure - and this means that in simple front lighting an incident meter's reading will normally match a reflective meter's reading from an 18% grey card.

[pico]

Thanks John -- It would seem to me then that if you have a spot reflective meter and point it at face you would have the same reading as if you did the same using an incident meter?

 

Having grown up with film, the rule for light skin is to open a stop more than the reflective reading. For dark skin, the reading is usually correct.

[Michael Geschlecht]

Hello JMR,

 

Welcome to the Forum.

 

Why do you think you have to choose 1 type of metering over the other?

 

There are any number of hand-held meters available today that make it easy to swich back & forth between incident & reflected/spot. These meters allow you to choose 1 type or the other (or both) depending on the individual circumstance.

 

One reason many photographers prefer incident metering when it is possible is that incident metering is often more acurate than reflected/spot metering in many photographic situations. Another reason for using incident metering when reflected/spot metering is equally accurate is that, compared to reflected/spot metering, incident metering is usually EASIER TO DO CORRECTLY.

 

It's pretty much foolproof in many situations:

 

Set ISO/DIN on the meter.

 

Stand in front of or in the same light as your SUBJECT.

 

Turn the measuring sphere on the meter in the direction of the CAMERA from the direction of the SUBJECT. Sometimes you might do this by standing along a parallel (NOT a converging) line to the camera.

 

Push the button & let it go.

 

Read the display.

 

Set the camera/lens

 

Take the picture.

 

There are some exceptions to this in some situations. But not that many.

 

Reflected/Spot light measurement is somewhat more complex. But not that difficult.

 

It takes somewhat more space to explain how to do reflected/spot metering than the explanation of incident metering written just above. This is the Forum to ask on if you want to find out how. There are any number of people here who will be glad to explain.

 

Either incident or reflected/spot is usable in most situations altho sometimes one of them is preferable. That is why it is better to have a meter that does both & allows a person to choose to use an incident reading or a reflected/spot reading on a photo by photo basis.

 

Sometimes you don't even need a meter. But that is another separate discussion.

 

Best Regards,

 

Michael

Edited September 20, 2014 by Michael Geschlecht

[MarkP]

So who is using what incident meter?

I wanted something compact and bought the little Sekonic L-208 a while ago but I hate it.

 

I want a hand-held light meter with the following features:

1. Incident and reflected (not fussed by spot).

 

2. Compact and light (so I can wear the cord around my neck with the meter sitting in a pocket when not using it.

 

3. Analogue - I'm such a Luddite but I like to be able to read off the aperture/shutterspeed combos as it's fast and efficient.

 

4. Good low-light sensitivity.

 

 

Any suggestions please?

[MarkP]

Yes - and the face will be placed in zone V regardless of skin tone. A very dark Papuan complexion will be rendered in the same grey as a very pale Finnish one.

 

see here

 

http://www.l-camera-forum.com/leica-forum/barnacks-bar/347260-niche-photography-interracial-weddings-d.html#post2786095

[Advertisement]

Hallo,

Look here: Interesting Leica gear

[IkarusJohn]

I use a Sekonic L-398A Studio Deluxe II, mainly because I'm a Luddite.