Why use Incident metering?
I have a newbie question about using an exposure meter. I have used the search function, but came up empty handed.
My question, simply, is why does a photographer use incident metering? I have gone through a number of publications and web-sites which explain how to spot meter and take reflective and incident measures, but nothing tells me why incident is useful. Instinctively, reflective and spot make sense, incident metering does not.
I have my doubts about the usefulness of reflective metering, but not incident and spot!
If your subjct is very light or very dark, and incident reading gives better results than reflective. On second thought - strike the "very". One stop lighter or darker than "18%" is enough to give a clear advantage to incident metering. It could even be of average tone, but strongly coloured - most reflective meters have a somewhat different spectral response than film.
With B&W and large format the spotmeter is king. For anything else, I use incident.
-- Ole Tjugen, Luddite Elitist
Good Morning, Kent,
Actually, for many subjects, incident metering makes more intuitive sense to me. The reading obtained simply measures light falling on the subject without taking into account the subject's degree of reflectivity. Unlike reflective metering, it involves no decisions on exactly where to aim the meter, no variables such as the color of the subject affecting the reading, etc. Naturally, a similar result can be obtained by using a reflective reading off a standard gray card. Consider that most studio use of flash meters is done in the incident mode, and that usually works out well.
There are going to be a lot of BZTS people chiming in, at least i hope, so I won't go that route. For me incident metering is like a really big averager. I use it most with color landscape. Yes, there are times I just hold it above my head and it has not missed. I only use my spot meter when I have tricky lighting.
In BW I seem to get consistent results with the incident meter.
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Owning and having used both types of meters, I find that I have consistantly better exposures using an $85 (circa 1984) incident meter then I do with my $400.00 + Zone VI modified digital spot meter.
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An incident meter gives you a reliable Zone V placement with one reading, so it's particularly useful in the studio, where you can control the contrast range of the scene by adjusting the light. It can also tell you the difference in output of different light sources by comparing the reading from one source to another source. The BTZS incident method, as I understand it (and BTZS users will correct me if I'm wrong, I'm sure), uses a variation on this studio technique to measure the difference between the direct light and shadow value to measure the contrast of the scene.
Spot reading depends on careful testing of your materials and previsualization, so that you can point the meter at an object and place that spot on a particular tone, just as if you were a painter with a palette of gray tones and the meter were a brush. The downside of this method, is that as it offers a certain amount of direct control, it's also open to a good deal of error--both in judgment and in placement when using a narrow spot. You can control two zones fairly precisely--the shadow value used to calibrate film speed and the highlight value used to calibrate development time--but zones in between or on the outside are going to fall where they may, and they might not always be where you want them to be.
Both methods can produce fine results as well as errors. An incident method can't really account for the reflectivity of objects in the scene--say, the difference between your average landscape and your average landscape with a shaft of light illuminating a brilliant white egret in the foreground, but if one is attuned to those situations, it seems to work in many situations for those who use it.
Personally--I usually use an incident meter for controlled lighting conditions and spot metering for landscapes.
A very similar question was asked on APUG a few days ago here. I'll restrain my urge to write more on the subject!
I go both ways also. Incident for studio and outdoor and reflective for out door. personally I find incident more accurate. Using a spot is easier to meter subjects further accurately I suppose but overall ambiance is ambiance everywhere within the environment your in, so a little intuition at the moment goes allot further in capturing the moment than does keeping yourself wrapped up in the tecknical. After a while you won't rely on meters very much at all. My suggestion would be to start with an ambient meter and use the spot meter inside your cameras to double check the range of exposure of your scene.
sorry to hi-jack the thread but i have a question for helen b -
hi helen -
i haven't read the minor white text you mention in the linked-thread, but
why did minor white suggest to use your hand rather than a gray card?
is it because no matter one's race the palm of the hand is 2 stops brighter than 18% gray? i sometimes use my hand because i can never remember where i put my gray card, and my hand is harder to misplace
There are two very similar threads, so it makes sense to transfer everything to one thread.
In the context of Minor White's method the important thing is that you use something consistently, and determine your effective film speed using that method (even more off topic, that's where he and many others differ from the 'Stouffer step wedge' method of film speed testing).
So the palm of your hand is convenient and readily available. As you have so astutely observed, you rarely leave it behind - unless it's your left hand and you are eating. It's also conveniently close to an 18% grey card in terms of diffuse reflectance (mine's about half a stop lighter than an 18% grey card).
If anything, I think that the question is 'why prefer your palm to an incident dome?' and, er, I can't think of an answer to that one - except the blindingly obvious reason (the sort I generally miss) that you can use you palm with a reflective meter or a camera TTL meter.
Sorry it's a bit rushed, hopefully others will chip in. It would be very interesting to hear from Minor...