Tom Rittenhouse wrote: > Paul, you are the one who said motion picture people use both spotmeters and > meters. In my experience they usually use an incident meter to set exposure, > and a spot meter to check reflectance. Then if the relectance of something > is out of range they adjust the lighting on it.
That makes sense to me because they have total control over their lighting. I can fully understand their approach because the lighting _must_ be consistent. However most of us don't have either the time or the resources available for that level of control, so we're left with two alternatives: 1) incident meter for the base exposure and let your scene's tonal range fall at the mercy of your film. You end up with a series of consistent exposures but depending on your film and subject matter you may end up with washed-out highlights and/or black shadow areas. I know I'm recycling my argument here but I should mention that a lot of my work involves some really contrasty scenery. Check out these two: http://www.digistar.com/~dmann/photography/gallery/cave.jpg http://www.digistar.com/~dmann/temp/trip/6x7-10-2001-s12-16_large.jpg I will also point out that I have been burned by subject reflectivity when using an ambient meter with colour slide film, and that really forms the basis of my decision to use a spot-meter (more on this below). 2) spot meter your shadows and highlights (and midtones) and end up with an exposure which holds detail right where you want it to, at the expense of the other end (or both ends) of the scale. Exposures won't necessarily be consistent because you'll be shifting your exposure to fall within the capabilities of the film, but you'll have exact knowledge of your scene's contrast range and with experience you'll know how it will be reproduced by the film (and printing, if appropriate). For a series of shots you can either leave your exposure as-is for consistency, re-meter, or just open/close a bit as you shoot based on the scene. Two different approaches, two different results. Both are "correct" and each has its advantages. As I see it, ambient metering gives you technical accuracy of your midtone while spot metering gives you the knowledge you need to take full control of your contrast range. If you mentally adjust your ambient-metered exposure due to subject reflectivity (eg lots of snow in the scene so stop down a little to preserve detail), you're just using the same process as spot metering but with less certainty (exactly how many stops is that snow above the midtone? How "bright" do I want it to look?). On the other hand, if you can't find a midtone in your spot-metered scene you need to take an educated guess of the base exposure, based on your knowledge of the film response and the subject matter. Zone-style systems try to eliminate the guesswork of the film and printing by controlling the post- exposure processes. But the only certain way to get a midtone reading with a spot meter is to get out a grey-card... but that's exactly the same as using an ambient meter to set your base exposure! This is why some of us tend to place certain parts of our scenery into a certain "zone". We know exactly what the relative brightness of everything in the scene is, and our knowledge of our film/printing gives us a good idea of how to adjust our settings to "set" that part of the subject to a certain brightness value based on what we want the result to look like. We might have to compromise if the "desired" setting ends up burning out a big highlight somewhere... but at least we'll know it's going to happen :) What's important to me is that with spot metering, you call the shots based on what you want your final picture to look like. So ambient metering requires an ability to read the range of light with your eye (or just faith in your film if you always use the indicated reading, or rules of thumb if your eye isn't experienced enough), and spot metering requires a knowledge of what your film and printing process is capable of. Both take considerable experience to get right, or so I'm finding :) That explains why I occasionally bracket. With the second image linked above, I couldn't quite decide between two settings a half-stop apart. So I shot both. It took a lot of effort to get there and I wasn't prepared to miss a nice shot when its only NZ$2 (about US$1) to make another exposure. The first shot was good, the second shot was _really_ good. Of course, someone with different preferences might prefer the first one (it has more shadow detail) so its just as well that I took both. With the ambient meter I would have had to bracket all over the place because I don't know where my shadows and highlights are going to end up. I want to know exactly what my contrast range is before I press the button. That's my perspective. Most of the time I don't even have the choice of which meter to use as the light I need to measure is beyond some obstruction (fence, cliff, mountain). I trust the spot meter not because its any better, but because it gives me all the knowledge I want to make my decisions. Now after writing all that, I'll relate a story from around New Year's where I learned that no matter what you do with your metering, the lab will screw it up :) I'd taken the 6x7 and the Z-1p to Wellington. For a couple of shots I decided to save effort of getting out the spot meter by metering with the Z-1p and adjusting the settings, because the Z-1p had Velvia loaded and the 6x7 had Provia 100F. A few hours later I realised that the Z-1p actually had E100SW (d'oh... the Velvia was in the K2 I was using a few days beforehand). I decided the underexposed pictures were more important than the first few frames on the roll, so I made a note to have the roll pushed, and set the meter to 200ISO for the rest of the roll. That was when I learned a lesson. The lab did not push the film, despite the envelope specifically stating "Push +1" (which I'd also written on the roll itself). If they weren't prepared to push a single roll of film they should have sent it back undeveloped! The last 3 or 4 frames on the roll were totally ruined due to underexposure, but the rest seemed OK (the ones I thought I'd screwed up were only about 1/2-stop out; I got bitten by extreme contrast again). Not a major loss (thankfully) but I will probably never ask for push-processing again. Cheers, - Dave David A. Mann, B.E. (Elec) "Why is it that if an adult behaves like a child they lock him up, while children are allowed to run free on the streets?" -- Garfield - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
