metering mode

[Yisehaq]

Explain some theory for me please. That is on how to use metering modes. Let me start from what I know about metering mode (spot, partial,evaluative,center weighed)all Canon I think.
Spot metering is fine with me I think. If I shoot something dark I close the Av down either one stop or two and white will be the reverse (18% gray scale thing) because one can measure small area.
My questions is can you use same priciple with other modes? How can that work say for evaluative and center (as it calculates the whole field of vision).

I would in fact appreciate if I can here a podcast on it. ;)
Anyways, I am sitting tight with my pen and paper.

[baddness]

I hope you get an answer because I have been wanting to know this as well.

[Travis]

I'm not sure what is unclear to you.... seems like you have the principle down...

Assuming using AP (AV)

Spot meter - measures a very small (about 3%) of your frame and suggests an appropriate shutter speed to correctly expose the 3% portion it is measuring

Center Weighted meter - measures about 60% of the frame and suggests an appropriate shutter speed. Center Weighted will also give small consideration the exposure value outside of the center area.

Matrix (evaluative) meter - measures the entire frame and compares the reading with several thousand algorithms preprogrammed into your camera. It then suggests an appropriate shutter speed based on a matching algorithm.

Matrix will nail about 90% percent(or more) of your general imaging but can be fooled in high contrast scenes. It doesn't know what part of the high contrast image you want to expose. Center weighted (and spot) allow you to instruct the camera to expose a desired area. Just be aware this can have consequence to the rest of the image. For example, you may spot meter the eye of person, and the resulting exposure will have a well exposed eye. However, the sky might be completely blown out, or shadows completely underexposed. You as the artist have to decide what is important. Matrix metering would pull in the sky and give you a more even image (except the eye would be slightly under exposed). You could dodge the eyes in pp though.

Each metering mode is a tool. They are all good, and you have to decide which tool is more applicable for the job. If shooting in a priority mode you are able to make exposure compensation adjustments to fine tune your result. If shooting manual then you decide the under/over exposure based on the meter.

[baddness]

so how do you get the metering? with a light meter?
You explained different meanings well, Travis, but not sure on how to get the metering.

[tirediron]

so how do you get the metering? with a light meter?
You explained different meanings well, Travis, but not sure on how to get the metering.

Using the light-metre built into your camera.

[baddness]

now something else to learn about my camera. I had looked it up in the manual but it didn't say how to use the built in light meter.

[Yisehaq]

Thanks Travis. could you please elaborate for me on center weighted? When is it prefered over spot or partial?

[Travis]

Thanks Travis. could you please elaborate for me on center weighted? When is it prefered over spot or partial?

Use Center when you want to expose a general area of the image (eg a body).. Use Spot when you want to expose a finite area of the image (eg an eye)...

A good way to see the difference... take your camera outside and park it AP(AV)...

Set you meter mode to spot and s l o w l y pan the camera around a scene. Notice the wild fluctuations in the shutter speeds when moving the camera just a small amount.

Now set your meter to center and s l o w l y pan the camera. Notice the fluctuations (while still there) are not as wild. This is because the camera is measuring a larger portion and is not as sensitive to small areas.

Now set your meter to matrix and s l o w l y pan the camera. Notice the fluctuation in shutter speed is very little (unless you point just at the sky and move to just earth). The lack of fluctuation is because matrix is measuring the entire frame and suggesting a shutter to balance the entire frame.

You can see your cameras meter through the view finder. Usually at the bottom you will see a zero in the middle followed by a plus/minus sign at either end. A little marker shows the exposure value. If you have your camera in AP/SP/P, the marker will always show in the zero position (unless you have adjusted your exposure compensation). In Manual mode, the meter shows how the image will be exposed based on your shutter and aperture settings. Put the camera in Manual and scroll either the shutter or aperture setting until the meter reads the zero position. Generally speaking this with ensure proper exposure.

[Yisehaq]

Thank you so much Travis.

"Use Center when you want to expose a general area of the image (eg a body).. "

Then am I right to assume that on center the area at the center and the area around will be given the same degree of exposure? if you measure the forehead that will be applied for the whole body?

let's take this example concerning the metering mode
http://www.photography.ca/Forums/showthread.php?t=1292
(I have got feed back on other issues)


I used martix for this thinking I will be interested in the whole image. I tried to over and under expose but the results are quite unsatisfactory at both ends. From your explanation, i think it was better spot metering on the faces. But also I wanted to show the design and texture of their dresses.
I am trying to get it inside me for once and for all.

Thanks a million again

[Travis]

The example shot is good for demonstration.

First, you should be aware due to contrast between deep black faces and bright white clothing this shot is beyond the dynamic range of a DSLR to properly expose. You may either pick to best expose the faces, best expose the clothing, or make sacrifice to both face and clothing to get a generally balanced image.

Spot metering the faces then spot metering the clothing would offer you to wildly different exposures.

Matrix metering is attempting to give you the best of both worlds. Matrix tends to give precedence to controlling highlights because blown highlights are not recoverable. Dark tones are often recoverable at the cost of noise.

You should also be aware that a large amount of black or white in a scene is likely to throw your cameras meter in a bit of tizz. This kind of scene requires the most attention by a photographer. An exp comp adjustment is likely, or better yet, switch to manual.

In this image, Matrix and Center weighted would most likely offer the same shutter speed/exposure.

[Yisehaq]

Just to add on point.

Does 18% gray scale theory (I think proper name is Zone system if I am not mistaken) work for all metering mode? Say Matrix? I have a feeling it only works for spot metering.

[Travis]

Just to add on point.

Does 18% gray scale theory (I think proper name is Zone system if I am not mistaken) work for all metering mode? Say Matrix? I have a feeling it only works for spot metering.


The zone system is pretty much the same a matrix (less all the measuring and calculating). In zone you are measuring the tonal range differences in the images and are choosing a shutter/aperture combo to average out those extremes. This is essentially what matrix does. Zoning was/is common with old filmers when matrix metering wasn't available yet. It's a benefit to learn but not a necessary to use nowadays. Even Brian Peterson (author of Understanding Exposure) a very popular book, admits that matrix metering is superior than zoning for most applications.


Try this link:

http://www.cambridgeincolour.com/tutorials/camera-metering.htm

[Yisehaq]

Thanks a lotTravis. That is so much help. I will try to go out and experiment.

I am just tired of not getting :o what I expect and doing a lot of :fingerscr. I am trying to make my brain think for me not my camera :eek: as usually is the case.;) What I want should be what I get.
I am very much grateful for your help