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06-04-2009, 01:57 PM   #1
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77 zone matrix metering

Many have doubted if more areas will equal better accuracy. Although I use center weighted or spot almost all the time, for matrix metering, at least historically, the answer is always yes - at least the possibility is there.

If all you use is spot or CW, you'll see almost no difference. It'll work better if you link AE to AF points.

Matrix metering works by taking EV's from the different areas, and apply some sort of algorithm to determine exposure. When the image is divided into more smaller areas, there are more inputs to the algorithms. For example, in the 77-area case, that bright reflecting watch is 5 areas away from the face, so maybe it can be ignored. In the 16-area case, it could be in the same area as the face, causing underexposure of the entire image.

There is another usage of these metering zones, which is to use them as inputs for a neural network which learns the EV from thousands of manually-metered images. In this case, too, more areas implies finer images during the learning phase, which hopefully results in better learning.

I know this post is an answer in search for questions, but since I have seen a few who are curious about the new 77 area metering, I hope I'm doing a service by providing some background info.

06-04-2009, 03:05 PM   #2
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QuoteOriginally posted by wolfier Quote
Many have doubted if more areas will equal better accuracy. Although I use center weighted or spot almost all the time, for matrix metering, at least historically, the answer is always yes - at least the possibility is there.

If all you use is spot or CW, you'll see almost no difference. It'll work better if you link AE to AF points.

Matrix metering works by taking EV's from the different areas, and apply some sort of algorithm to determine exposure. When the image is divided into more smaller areas, there are more inputs to the algorithms. For example, in the 77-area case, that bright reflecting watch is 5 areas away from the face, so maybe it can be ignored. In the 16-area case, it could be in the same area as the face, causing underexposure of the entire image.

There is another usage of these metering zones, which is to use them as inputs for a neural network which learns the EV from thousands of manually-metered images. In this case, too, more areas implies finer images during the learning phase, which hopefully results in better learning.

I know this post is an answer in search for questions, but since I have seen a few who are curious about the new 77 area metering, I hope I'm doing a service by providing some background info.
Some speculation.. each segment is .04 inches square... spotmeter will no longer be round but part of a square grid..
06-04-2009, 06:46 PM   #3
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I'm looking forward to seeing how this new metering system performs. Underexposure due to hot spots off center is my biggest pet peeve with the meetering system with my K10D.
06-04-2009, 08:01 PM   #4
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QuoteOriginally posted by Robert S Donovan Quote
I'm looking forward to seeing how this new metering system performs. Underexposure due to hot spots off center is my biggest pet peeve with the meetering system with my K10D.
The guy who owns the PDML, judges the GFM Nature Photography Weekend, among other things photographic got to play extensively with a preproduction camera (firmware 0.35, IIRC). He reported that the metering is in fact vastly improved.
As I've always found metering on Pentax to be their real Achilles Heel, I'm thinking this is a good thing.
Dare I say that if it is as good as he says, it might be considered Pro Grade?

06-04-2009, 08:10 PM   #5
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QuoteOriginally posted by Wheatfield Quote
The guy who owns the PDML, judges the GFM Nature Photography Weekend, among other things photographic got to play extensively with a preproduction camera (firmware 0.35, IIRC). He reported that the metering is in fact vastly improved.
As I've always found metering on Pentax to be their real Achilles Heel, I'm thinking this is a good thing.
Dare I say that if it is as good as he says, it might be considered Pro Grade?
There are no professional cameras, only professional photographers. Oh wait. Wrong thread
06-04-2009, 10:00 PM   #6
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QuoteOriginally posted by jeffkrol Quote
Some speculation.. each segment is .04 inches square... spotmeter will no longer be round but part of a square grid..
If true, what would be the downside to this, if any? To me, it makes no difference as long as I know the size...
06-05-2009, 05:42 AM   #7
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QuoteOriginally posted by jeffkrol Quote
Some speculation.. each segment is .04 inches square... spotmeter will no longer be round but part of a square grid..
Hmmm, I wonder if we'll be able to have the spot-meter follow the AF point now...
06-05-2009, 05:44 AM   #8
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QuoteOriginally posted by RBellavance Quote
Hmmm, I wonder if we'll be able to have the spot-meter follow the AF point now...
It already can. Pentax customer service confirmed to me that the menu item to link AF point to exposure turns matrix metering into spot metering which follows the AF point.

06-05-2009, 06:53 AM   #9
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QuoteOriginally posted by mattdm Quote
It already can. Pentax customer service confirmed to me that the menu item to link AF point to exposure turns matrix metering into spot metering which follows the AF point.
I really hope that's a misunderstanding.

As I've understood the Link AE to AF point feature it is still Pattern metering, but it weights the active point as it is senterpoint. Have I got this wrong?
If so, that could explain a lot of my metering problems with K10/20D.
06-05-2009, 07:04 AM   #10
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QuoteOriginally posted by mattdm Quote
It already can. Pentax customer service confirmed to me that the menu item to link AF point to exposure turns matrix metering into spot metering which follows the AF point.
Unfortunately (or fortunately, I would be disappointed if Matrix did not remain Matrix ), that does not seem to be true.

If that were the case, with "Link AF point to AE" enabled, Matrix metering using the center AF point and Spot metering should give the same metering for a given scene. And that is not what happens, I just tried it.

Maybe JCPentax could shed some definitive light on this ? I've asked the question in the "K-7 Features Questions" thread.

Last edited by RBellavance; 06-05-2009 at 07:34 AM.
06-05-2009, 08:19 AM   #11
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QuoteOriginally posted by mattdm Quote
It already can. Pentax customer service confirmed to me that the menu item to link AF point to exposure turns matrix metering into spot metering which follows the AF point.
Sorry, they gave you incorrect information. It simply biases the exposure to the focus point.
06-05-2009, 05:36 PM   #12
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QuoteOriginally posted by JCPentax Quote
Sorry, they gave you incorrect information. It simply biases the exposure to the focus point.
Thanks. Here's the message I got:

Code:
Dear Mr. Miller,

Thank you for contacting Pentax.

It is spot metering, but on the focus point, rather than on the center, which is
essentially what you are saying in B.

Best Regards,
Dorian B.
Pentax Imaging Technical Support

Your Email:
Hi. I'm hoping you could clarify something regarding the "Link AF Point and AE"
setting in the K10D. The manual does not provide very much information.

When this option is enabled, there are three possible ways I can imaging the camera
acting:

A) The multi-segment metering intelligence is still functional, taking all 16 zones
into account, but weighting the exposure towards the zone
containing the focus point.

B) Only the zone containing the focus point is considered -- effectively, spot
metering on the focus point rather than the center 2.5%.

C) The metering is weighted around the focus point as in center weighted metering,
but again, not using the center.

Which of these answer is correct? (Preliminary experiments indicate that it seems
to act like "B".)

Thank you!
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