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Old Mar 7, 2003, 9:15 AM   #1
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Default How does 256- segment Matrix AF work?

How does the Nikon 2100's 256- segment Matrix linked to AF area work? I was wondering how it compares to the three point and five point autofocusing system used by other cameras.

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Old Mar 7, 2003, 12:18 PM   #2
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anyone?
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Old Mar 7, 2003, 12:22 PM   #3
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Not Matrix AF, it's Matrix (light) metering:

From http://www.digitalsecrets.net/secrets/N880.html

"...the Matrix meter divides the scene up into 256 zones. A checkerboard of rectangles 16 x 16 units, each of which is its own light meter."
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Old Mar 7, 2003, 12:24 PM   #4
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I have no idea personally.

However, I found the following from NK Guy's excellent website (www.photonotes.org):

******************

Matrix metering.

(Nikon) An automated through-the-lens camera metering system used by Nikon.

The scene is divided into a number of discrete cells which are metered independently. The camera’s CPU then examines each cell and compares the result to an internal database of prestored lighting conditions. The camera then chooses an appropriate metering setting accordingly.

Matrix metering is indicated on cameras by a matrix metering icon. Canon’s name for its similar system is “evaluative” metering.

**************

Perhaps not too detailed, but it's a start...
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Old Mar 7, 2003, 12:58 PM   #5
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Quote:
How does the Nikon 2100's 256- segment Matrix linked to AF area work?
... Basically it's everything that was already said except the lightmetering put more weighting in the area the camera focus on.

For example a picture of a panoramic scene with a higlighted subject on the right half of the picture where a person is standing in the near field (and where the camera has focused on). The camera would put more emphasis on metering the subject, rather than the distance landscape where it's not critical, or it the picture could be too dark instead (ie if the person is wearing darker clothes or have different EV value than the rest of the 256 segments)!
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Old Mar 7, 2003, 1:14 PM   #6
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Thanks for all the info guys .
Also, how effective is this method compared to other methods used by other manufacturers?

Thanks,

Shiggy
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Old Mar 7, 2003, 1:18 PM   #7
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Also, how effective is this method compared to other methods used by other manufacturers?
They are all pretty similar, but all given fancy names... and always can be fooled by tricky lighting. Your eyes and brain are the most accurate... use spot readings @ key points and do the 'matrixing', 'evaluation' and 'linking' yourself!
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Old Mar 7, 2003, 1:26 PM   #8
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Is it as effective as the three point and five point autofocusing that is used by other cameras? I am sorry if I am being redundant :?

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Shiggy
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Old Mar 7, 2003, 1:27 PM   #9
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With matrix, you have to trust that the camera has chosen the right subject, or if there's multiple subjects your camera may be choosing an overly bright one and mess up the rest of the picture.

With Centre-Weighted, the camera measures the whole scene but concentrates more within the centre of the scene where the most important objects are usually located.

With Spot metering only evaluates the small area in the centre of the viewfinder instead of averaging the whole scene.

I prefer the last two over matrix because I have more control over what the camera does. If I want the subject off centre, I can first centre the subject, lock the exposure, and then frame the picture.

The whole point of metering is to reach "middle gray". There's a whole section on exposure meters in the free online "book" at http://www.photocourse.com/05/05-00.htm
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Old Mar 7, 2003, 1:33 PM   #10
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Quote:
Originally Posted by shiggy
Is it as effective as the three point and five point autofocusing that is used by other cameras? I am sorry if I am being redundant :?
(Exposure) metering and focusing are two different things and use different methods. As I said above metering is trying to average the scene to middle gray. Focusing is explained here:

http://www.howstuffworks.com/autofocus3.htm
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