Light Meters
robdavis305
Registered Users Posts: 1 Beginner grinner
I understand the ISO but have trouble knowing what to set aperture and shutter speed on. Does a meter tell you what settings and are they worth the money.
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Your profile says you own a Nikon D90. It has a fine reflected light meter in it. Do you use it? Do you understand how it works? Do you understand what aperture and shutter speed mean in the context of photography?
Your camera's light meter will give you the correct aperture and shutter speed for a given exposure if you understand how to interpret it. It is not always accurate and will not meter the way you may expect. The reflected meter in your camera ASSUMES the world is a medium gray tone. If your subject is not a medium grey tone, you will need to adjust your meter readings to a more appropriate value.
With your camera in Manual Mode, the meter will help you select a proper aperture and shutter speed. The aperture and shutter speed are linked, that is at a given ISO, if you change one you must also change the other.
Aperture is what it says it is - a number that describes how large the hole in the aperture diaphragm in the lens opens to admit light. f16 is a very small aperture, f11 admits exactly twice as much light at f16, f8 doubles it again, as does f5.6, f4, f2.8, f2 etc. Shutter speeds typically come in 1/1000th, 1/500th, 1/250th, 1/125th etc
THese are set up so that 1/1000th at f8 ( at a given ISO ) admits the same amount of light as 1/500th at f11, or 1/250th at f16.
So when you adjust your camera ( in fully Manual Mode ) you need attend to both aperture and shutter speed, if you change one, you may need to change the other as well to maintain the same exposure.
If you shoot in Av mode, the camera will choose the shutter speed according to the aperture you have selected, based on your meter. In Tv mode, you choose a shutter speed and the camera will select and aperture.
If you shoot a snow scene the meter reading will lead to under exposure because it sees a grey scene not a bright white scene. YOU will need to adjust the meter to add about 1.5 stops more light for a snow field. If you shoot a black panther in a coal mine, YOU will need to subtract about 1.5 stops of exposure since you want the panther to look black, not grey again,
A handheld Incident light meter is more accurate than the reflected light meter in your camera, but the meter in the D90 is excellent if used with skill and understanding. Pros get excellent images with the D90 and its meter.
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1. Does the meter tell you what settings to use? Yes - it will suggest possible "correct" exposure settings. But, they are not always what you want. What an incident light meter reads, if the light meter is placed in light similar to that illuminating your subject, is the amount of light falling on your subject. When you enter one of the three exposure factors (ISO, aperture, shutter speed), it will display for you combinations of the other two that will make for a "properly" exposed image. On the Sekonic L-358, the light meter with which I have the most experience, one can set the desired ISO and have displayed the various "appropriate" combinations of aperture and shutter speed. What's really cool is that, with just one reading, you can then change any of the exposure factors and get combinations of the others - no need to take a second reading (unless you want to
2. Are they worth it? As with most things photographic, "It depends." Like PF said, the reflected light meter in your camera (as in most current cameras) is quite good. It takes some experience to properly interpret the data the camera light meter is providing. Like PF said, the camera light meter assumes the scene it is metering is 18% gray (as most green stuff - plants - in our world closely approximates 18% gray and most of our world is filled with this green stuff). But, in situations where this assumption doesn't hold (the beach in the sun, snow, a groom's tux, a brides wedding gown, a black labrador retriever), the photographer must know how and to what exent to over-ride the data supplied by the camera meter to get a "proper" exposure. In the case of a snow filled scene, one would have to add 1 1/2 to 2 stops of exposure to turn that snow white - otherwise it will be gray. The man's black suit or the black haired dog - you would want to decrease the exposure by about 2/3 stop or his tux will be gray rather than black. If you can't (because you lack the experience) or don't want to supply the brain power necessary to over-ride the camera reflected light meter, then the hand-held incident light meter may very well be worth the money.
Shooting with off-camera light (hot-lights, strobes, manually adjusted lighting) is another situation where having a light meter really saves time. But, that's a whole other discussion that has been covered in some detail in other forum posts. You can get a good start of finding those with the following google search:
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I am puzzling with the same question posed by the OP. I find the metering on my 40D to be a bit clunky, and if I shoot on automatic the camera gets it wrong more often than I would like. I recently changed my way of working, stepping back many years, to first spend a few minutes thinking about the light before stepping out of the door to shoot and then using the camera in M mode to check exposure settings before taking shots - results are improving.
It would certainly be easier to check the light with a seperate meter, and likely the results would be a bit more accurate too. But the in-camera metering is "good enough" for 99% of cases- I just need to learn how to read it better. Finding the right way of working on a dslr is still a puzzle for me.
If you leave on the default, every point in the image is equally weighted, so if there is abright spot off to the right of your image (an open window), you get underexposure because of the big light source. The next two reduce the metering area to either the center area around the 7 center AF points or an area within those points. The final onw has a is sort of a mix of the first and second where you have most of the information from the larger center weight and then some information from everywhere else.
So you have two things you need to think through to get the right exposure:
1) How neutral is the metering area (Snow Bank or Coal Mine)? Use the exposure compensation to adjust (+ for bright images, - for dark).
2) How large of an area do I want to account for? If there is a lot of back-light and you aren't trying to preserve details there, you need to use center-weighting to avoid a dark forground (or use a fill flash).
I'm still learning here, but I hope this helps. You should be able to get proper exposure from the on-camera meter.
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