Metering and Exposure

[lfoush]

I understand the basics of the different types of metering on a dSLR (matrix, spot, etc.), and I also understand how to adjust settings on the camera yourself such as ISO and aperture to get a proper exposure. What I don't understand very well is how the two tie together. What's the difference for example between having your camera on matrix metering with settings of f/ 5.6, ISO 200, and a shutter speed of 1/500 and having your camera on spot metering with those same settings? I know the answer is probably obvious, but I just don't understand how the two correlate. Any help would be great!

 

[Light Guru]

What's the difference for example between having your camera on matrix metering with settings of f/ 5.6, ISO 200, and a shutter speed of 1/500 and having your camera on spot metering with those same settings?

The difference is when using each of those different metering modes your camera may not tell you that those settings will provide a proper exposure even though they are both looking at the same seen.

All the metering modes do it let you choose how the camera is going to look at the screen to pick the exposure.

 

[bsinmich]

Spot metering will measure a very small spot in the center of the area (usually 2-3 degrees). Matrix will take readings of multiple areas in the picture and give an average exposure. Soit will let you take a reading of an object that is in the scene but not lit to the same degree as the rest of the scene.

 

[Patrice]

If as you say your camera settings are iso 200, f/5.6 and 1/500, which suggests manual mode, then no matter what metering mode you use you will get the same picture because you have not actually changed anything.

 

[thetrue]

The meter gives you an approximation as to how much light the sensor will be exposed to. I don't like matrix metering for scenes that have large variations in light because it basically measures the overall scene rather than your subject, so to me spot metering is the way to go. You may find that you like either matrix or center weight better. When you are in manual, you set your ISO, aperture, and shutter yourself. After you change those settings, you will half press the shutter button for AF and at that point in the viewfinder you will see a bar with an arrow. Wherever that arrow lies on that bar will tell you if your photo will be over- under- or properly exposed based on its position on that bar. Best way to learn is to try different settings and watch the arrow move.

 

[greybeard35 7]

All those different modes do is what they have done to you and that is confuse things. All metering methods are searching for the holy grail of metering and that is 18% gray. Amazon.com: Gray Card 18% R-27: Camera & Photo.

In spot mode it meters a small spot usually from the middle of the scene and assumes it is 18% gray. In matrix it looks at the entire scene and averages it down to 18% gray (with some tricks of comparing it to a bank of scenes stored in the computer memory). And, in center weighted it meters well center weighted. I get the most consistently correct exposures by spot metering on a gray a card in the scene 1st, and then using what ever exposure recommendations I get from that reading. This is exactly the same as using an incident meter, measuring the light falling on the scene, even though I am measuring the light reflected from a gray card.

 

[tirediron]

.... What's the difference for example between having your camera on matrix metering with settings of f/ 5.6, ISO 200, and a shutter speed of 1/500 and having your camera on spot metering with those same settings?

The difference is, that in Matrix Metering, the image as a whole should be reasonably well exposed. In spot metering, depending on the what you metered, it could result in only a very small area being correctly exposed.

 

[thetrue]

Unless I somehow failed the "Matrix Metering" portion of learning, every time there are drastic differences in light, either the brighter or darker portion of my photo is reasonably well exposed....can you shed any light on this for me tirediron? (No pun intended)

 

[tirediron]

Unless I somehow failed the "Matrix Metering" portion of learning, every time there are drastic differences in light, either the brighter or darker portion of my photo is reasonably well exposed....can you shed any light on this for me tirediron? (No pun intended)

Sorry, it's early and my coffee level is still a quart low; I'm not following. To explain my previous post another way, "Matrix mode is meant to meter the entire viewfinder, spot metering a very small (usually <2 deg) area".

 

[KmH]

Matrix/Evaluative averages the light in the entire scene, and biases the in-camera light meter accordingly. Bright areas may be over exposed, dark areas may be under exposed. That depends on the dynamic range of your camera.

Center-weighted metering gives about 75% weight to the center 10% or so of the scene (25% to the remaining 90% or so of the scene), and biases the in-camera light meter accordingly. Often recommended for doing portraiture.

Spot metering only meters 2% -3% or so of the scene, and biases the in-camera light meter accordingly.

Note - When using Nikon DSLR cameras in Spot metering mode, the spot metered is tied to the selected auto focus point if a single focus point mode is also selected.

It is my understanding that when using a Canon DSLR in Spot metering mode the spot used is always in the center of the scene.

 

[rambler]

KmH: Teach a man to fish, and you will have a guy who sits in a boat and drinks beer all day.

Isoufh: In general, use center-metering when your subject is a relatively small part of the frame or when it is lighted differently than the rest of the scene, eg. light in one part, shade in another. Use spot-metering when you want to shoot a very specific part of your subject even a smaller portion than what you would use with center-metering. eg. the center of a flower blossom that is in different light than the rest of the frame.

Try the different settings on the same subject without moving your tripod. For example try it on the side of a house with maybe sun on the wall and the roof in shade or the other way around.

(Thanks to Lynne Eoidce and a course at BetterPhoto.com "Tips for Great Exposures")

 

[SCraig]

I understand the basics of the different types of metering on a dSLR (matrix, spot, etc.), and I also understand how to adjust settings on the camera yourself such as ISO and aperture to get a proper exposure. What I don't understand very well is how the two tie together. What's the difference for example between having your camera on matrix metering with settings of f/ 5.6, ISO 200, and a shutter speed of 1/500 and having your camera on spot metering with those same settings? I know the answer is probably obvious, but I just don't understand how the two correlate. Any help would be great!

You are confusing METERING with EXPOSURE. Exposure (actually Exposure Value) is the amount of light allowed to reach the sensor when the shutter is opened based on the combination of shutter speed, aperture, and ISO that are set on the camera, either manually or by the metering system. Metering is the camera's calculation of the proper values of aperture, shutter speed, and ISO that will provide a proper exposure based on how the meter is set and how it interprets the scene.

If you are shooting in manual mode there is no difference whatsoever since the camera could care less what the meter is telling it to do. The fact that you are in manual mode allows you to set the exposure settings and the camera ignores the meter. If you are in any other mode the meter will calculate one or more exposure settings (aperture, shutter speed and/or ISO) based on what the meter is telling it. See all the previous posts above for more information.

 

[Derrel]

Unless I somehow failed the "Matrix Metering" portion of learning, every time there are drastic differences in light, either the brighter or darker portion of my photo is reasonably well exposed....can you shed any light on this for me tirediron? (No pun intended)

Ummmm....that's a great oversimplification...in the newer Nikons, the camera can measure the entire tonal range (dynamic range, in EV values), measure color of objects and not just their degree of reflectivity, but their actual RGB makeup, can incorporate the focusing point, and incorporates the day,date,time,city location on world map (and thus determines the season of the year, and of course 'day' or 'night'), and also measures the distance the lens is focused at, and then runs the information against an in-camera computer-stored database of actual photographs and their exposure analysis data. ALL of that information, and more!, is used to determine both exposure, and dynamic tone curve adjustment (AKA D-Lighting) in an effort to control both 1) exposure and 2)tone curve.