Good afternoon everyone,
I'm posting this in the film thread, because I shoot film (B&W). I know it's applicable to digital photography, but I've found film photographers tend to have slightly different ideas of methodology. I would welcome insight from anyone, though.
I've been feeling overwhelmed with all the different metering concepts. Not so much the matrix/center/spot concept, but the following:
1. Reflective metering.
2. Incident metering.
3. Using a grey-card.
4. Using the zone system via spot metering.
How the heck do you choose with "method" to use?
In my experience, they all come out slightly different. Close, but usually different within a stop or two.
If someone could compartmentalize this a bit for a novice sake, that'd be awesome.
Thank you!
Let's see here. I'm going to take your list backwards.
4. Are you doing your own darkroom work -- your own film processing and printing? If not then you can't use the Zone System. Few aspects of photography are as misunderstood as the Zone System. Integral and fundamental to the Zone System is the variable gamma performance of film over development time. If you haven't tested the film you're using and aren't processing that film at different times to manipulate it's gamma output in response to exposure and then likewise manipulating the printing process then you're not using the Zone System and you really can't. I'm going to make an assumption here that you're not doing that because you wouldn't have otherwise asked this question. So you can strike #4 off your list as: you've encountered misinformed fauxtogs spewing nonsense.
4a. Spot metering: Spot metering is a good way to go but it requires auxiliary support. Let's take auxiliary support and save that as a topic to treat after we work further through the list.
3. Using a grey card for metering is a way to try and get a reflective meter to mimic the performance of an incident meter. You could also think of it as a way to carry around your own spot to use use for spot metering. It does have that element of consistency when used to replace spot metering but unfortunately it will likewise require auxiliary support.
2. Incident metering: The whole point and advantage of incident metering is that you're measuring the light intensity from the source before it has been altered by the reflective properties of the subject. There's a real appeal to that. By cutting out the change in light intensity that the subject causes you can look forward to increased consistency. When using an incident meter what you're doing is determining the exposure that correctly places a diffuse highlight, setting that exposure and then assuming everything else will fall into place. The trick with an incident meter has to do with my use of the verb "assuming" in the last sentence. It's a fair assumption some of the time until it's not at which point you're going to need auxiliary support.
1. Reflective metering: Here you're measuring the light reflecting back from the subject. Given that different subjects have different reflectance rates (white painted house versus dark brown brick house) this begs the question, how does the camera meter know the difference? And the answer of course is it doesn't. So then how do we know if a reflective meter reading is accurate? And the answer is we don't. So guess what we're going to need: auxiliary support.
Here's a couple photos that illustrate the reflected light issue:
I saw the two cars parked together across my street and grabbed my camera because it was a good illustration to use for class. I took the photo of the two cars together -- one silver and one charcoal. The exposure is good for both. Then I moved in close and took the silver car door panel and then the charcoal car door panel. Those photos are side by side in the bottom of the illustration. You can see that the meter darkened the silver car door panel and lightened the charcoal car door panel. Unable to discriminate that something is actually lighter or darker, that's how a meter works.
An incident meter would have given me very close to the same exposure I used for the photo of the two cars. The diffuse highlight is well placed using my camera's reflected meter.
Auxiliary support: Let's look at a problem photo that will introduce "auxiliary support."
That's J. B. Kleinpeter pushing a load of coal up river past one of my favorite fishing spots. I only had a pocket camera with me that used a reflected meter. I took the top photo and when I did I brought in auxiliary support. I said to myself, "got a white painted tow in direct sun making up at best 20% of the frame area in an otherwise normal but high contrast (sidelit) landscape. If I let the camera's meter set the exposure it'll nuke the diffuse highlights." I then intervened and reduced the exposure 2/3 stop. And sure enough you can see that the top photo is too dark and appears underexposed. I did that. That was better than what the camera would have done (middle frame) blowing the highlights. I had two choices: 1. bad and 2. worse. I picked bad knowing I could effect a repair whereas worse would have been a basket case. The bottom frame is my repair of the top photo.
Would an incident meter have given me a correct exposure? In this scene was there a correct exposure? In fact an incident meter would have given me very close to the top photo. Because an incident meter is designed to give you the exposure that places the diffuse highlight it will tend to give you photos that appear underexposed in very high contrast light. The one advantage in a case like this is that the incident meter would have given me bad whereas the reflected meter would have given me worse. Does it matter if I understand what to do in both cases? You and me, we're auxiliary support.
Let's bring back the Zone System for a minute. The Zone System photographer would begin by measuring the scene dynamic range. Neat trick there: they're slow but that tow is moving. So our Zone System photographer is going to have to be blisteringly fast. Their calculations would have told them the scene contrast range was high and that they would have to compress it by reducing the film gamma in processing. They would expose to brighten the image over what I did but hold the diffuse highlights with that pulled film processing. Then in the darkroom they're likely to need a higher grade paper. The Zone System was designed in the first place as a way to accommodate lighting conditions that pushed on limits. It's auxiliary support that includes messing with the chemistry. You're not messing with the chemistry right?
So reflected, which includes spot, and incident. If you go spot you need to pick the right spot and that still doesn't tell you what kind of lighting contrast you're dealing with (neither do reflected or incident). So no matter which way you go you're going to need auxiliary support. Auxiliary support is you learning to see the light and along with understanding how your hardware works
(because you've tested it!) make the call. No matter which way you go you're going to need auxiliary support. In other words you have a skill to learn. Now lets make that as easy as possible: Don't confuse yourself with too much variability. Pick the most convenient metering method (reflected most likely) and learn that skill. You'll get there faster by concentrating on mastering that skill without variation or distraction.
Joe