Types of exposure

[rahuldg11]

Can someone explain to me the differences between matrix metering, partial metering and spot metering ? and when to use these ?

[teaking]

Metering is just a way to evaluate a scene in terms of light (the dynamic range of the scene). Your camera is trying to change the exposure for the average amount of light. Its a method that works well for a lot of scenes but not The idea is if you exposure for the average amount of light in the scene chances are your photo will be exposed properly.

How your camera does this is with metering modes centre weighted takes the centre part of the image and pays more attention to this, spot metering will do the same but more extreme and use a small region only, matrix will take the whole scene divide it up and then average each section before putting it all together.

Matrix or evaluative metering is commonly used in conjunction with EV compensation to give good results for most scenes. Where spot metering is sometimes used for portraits to expose for small areas such as skin. But once you know the different modes you can choose the best one for the scene your shooting, I would recommend reading your cameras manual as they usually have a section covering your cameras metering modes.

*** Edited to fix crappy spelling ***

[RichardTaylor]

This may help also.

Introduction to Metering Modes

[dcclark]

I'm not trying to be harsh, but I understand these exposure modes, and I had trouble understanding teaking's explanation.

A quick rundown: your camera is trying to determine the correct amount of light to let in to the camera. It does this by choosing a shutter speed, aperture, and ISO. How it chooses the appropriate combination is determined by the metering mode:

- Matrix Metering: the camera evaluates everything you can see through the lens. It takes into account the varying amounts of brightness from different parts of the scene, where your lens is focused (to help determine which part of the scene is most important), and often it uses the colors in the scene as well. Think of this as a "general overall good compromise" choice.

- Partial metering: The camera chooses only one small area of the scene to evaluate for brightness, and pays only a little attention to the rest of the scene. This small area is usually where you're focused, so it's like telling the camera "here's the most important thing in the scene -- please pay attention to it."

- Spot metering: Like partial, but it really ONLY evaluates one small spot. This lets you expose one small spot correctly, and let the rest of the photo do whatever it will do. This helps in tricky lighting situations, where matrix metering will try to choose a "compromise" exposure which results in NOTHING looking quite right.

Good luck!

[teaking]

No problems here the more ways something is explained the greater chance someone will understand

I guess I tried to cover everything quickly... too quickly lol

[rahuldg11]

Is there a separate meter in the camera for this metering purpose ? If not, how does the camera know when i am using what kind of metering? I mean, what changes in the camera when i choose partial metering instead of matrix metering?

[teaking]

Its the same meter in the camera the only thing that changes is the way the camera analyses the scene to make the exposure, It is changed in the metering heading in your camera options menu.

[rahuldg11]

That is not exactly the answer i wanted. Like we know that the aperture opens and closes like the iris of the eye, when we change the f stop, there must be some change in the camera when we change the metering...what is it?

[teaking]

what is it...... well the answer you may want to read is in your camera manual

The change in the camera is the software or program routine that is run to decide the exposure. The hardware is the same and the same meter is used.

DC Clark wrote what I consider a really good post on the metering modes and what they do and how they work which was much better than my attempt. And I think that post will explain what is happening in different metering modes.... if you want more detailed information try google

[inkista]

Originally Posted by rahuldg11

That is not exactly the answer i wanted. Like we know that the aperture opens and closes like the iris of the eye, when we change the f stop, there must be some change in the camera when we change the metering...what is it?

Nothing physically changes in the camera (unlike shutter speed or aperture), or electronically changes (as in iso: voltage gain across the sensor). What changes is the algorithm used to select the data, chew on it, and spit out a result.

This is digital photography. While we see an image on the sensor, what the camera processor sees from the sensor is a ton of numerical data. Should it consider all the pixels? Or just the ones in a certain area? Should it simply average all the numbers? Or should it give specific weight to certain areas or certain values? The camera company comes up with what it thinks are the optimal algorithms for certain situations, and then programs them into the processor and gives you your choice.