Linking AF point and AE during multi-seg metering

geckogrin · 08-21-2010, 05:40 PM

Looking at p. 99 of my manual for my K20D and trying to understand better about spot metering. . .

It says here in the Custom Setting menu, you can choose OFF or ON (OFF is default).

OFF means exposure is set separately form AF point in multi-segment metering.

ON means exposure is set in accordance with AF point.

I'm not sure I understand how this would play out in a practical example. Which do you use, and why? Thanks.

dlacouture · 08-21-2010, 05:54 PM

Well, think "focus-point-weighted" : it will take the current focus point and use it to meter the scene (but still using the whole matrix to evaluate what you're trying to do : contre-jour, etc).

So, if you've selected the top-left focus point, it will meter so this area will reach 18% gray.

It's useful if you select your AF points a lot, or use the Auto selection... If you stay on the center point, then you'll have something like center-weighted on steroids (with some matrix-metering bells and whistles)...

aleonx3 · 08-21-2010, 06:45 PM

If you select the OFF option, then no matter what the focus point is selected, the multi-segment metering is fixed once the frame (scene) is set. This only affects multi-segment metering though not spot or center weigh. This is useful when exposure to the subject focus point is vastly different, such as black and white person's face, or black and white dresses within the same frame.

MSM · 08-21-2010, 07:59 PM

Originally posted by dlacouture

Well, think "focus-point-weighted" : it will take the current focus point and use it to meter the scene (but still using the whole matrix to evaluate what you're trying to do : contre-jour, etc).

So, if you've selected the top-left focus point, it will meter so this area will reach 18% gray.

It's useful if you select your AF points a lot, or use the Auto selection... If you stay on the center point, then you'll have something like center-weighted on steroids (with some matrix-metering bells and whistles)...

That is my understanding too. One other point that is sort of relevant here. If you use this feature and use the center focus point and a split prism (Katz eyes) with a slow max aperture lens say >f/3.5, you will have a lot of issues with metering. I found this out with my K10D. In other words, when using this feature the camera does treat the focus point as a quasi spot meter. Using a spot meter mode with a Katz eye prism and a slow lens will cause metering errors. In my case, it was significant > 2 stops over exposure.

This feature would be handy say if you were taking a portrait and the model was in the light and the rest of the background was dark and s/he was off center and you wanted to frame the shot and then move the focus point over the model. Of course, you could spot meter with the center point and then recompose, too.

08-21-2010, 05:40 PM	#1
geckogrin New Member Join Date: Oct 2009 Location: Northern VA Posts: 19	Linking AF point and AE during multi-seg metering Looking at p. 99 of my manual for my K20D and trying to understand better about spot metering. . . It says here in the Custom Setting menu, you can choose OFF or ON (OFF is default). OFF means exposure is set separately form AF point in multi-segment metering. ON means exposure is set in accordance with AF point. I'm not sure I understand how this would play out in a practical example. Which do you use, and why? Thanks.

08-21-2010, 06:45 PM	#3
aleonx3 Veteran Member Join Date: Jul 2007 Location: Brampton, Ontario Photos: Gallery \| Albums Posts: 3,996	If you select the OFF option, then no matter what the focus point is selected, the multi-segment metering is fixed once the frame (scene) is set. This only affects multi-segment metering though not spot or center weigh. This is useful when exposure to the subject focus point is vastly different, such as black and white person's face, or black and white dresses within the same frame. Last edited by aleonx3; 08-21-2010 at 06:49 PM. Reason: more explanation

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08-21-2010, 05:54 PM	#2
dlacouture Veteran Member Join Date: Jul 2008 Location: Var, South of France Photos: Albums Posts: 1,074	Well, think "focus-point-weighted" : it will take the current focus point and use it to meter the scene (but still using the whole matrix to evaluate what you're trying to do : contre-jour, etc). So, if you've selected the top-left focus point, it will meter so this area will reach 18% gray. It's useful if you select your AF points a lot, or use the Auto selection... If you stay on the center point, then you'll have something like center-weighted on steroids (with some matrix-metering bells and whistles)...

08-21-2010, 07:59 PM	#4
MSM Veteran Member Join Date: Dec 2007 Location: Alabama Photos: Gallery Posts: 994	Originally posted by dlacouture Well, think "focus-point-weighted" : it will take the current focus point and use it to meter the scene (but still using the whole matrix to evaluate what you're trying to do : contre-jour, etc). So, if you've selected the top-left focus point, it will meter so this area will reach 18% gray. It's useful if you select your AF points a lot, or use the Auto selection... If you stay on the center point, then you'll have something like center-weighted on steroids (with some matrix-metering bells and whistles)... That is my understanding too. One other point that is sort of relevant here. If you use this feature and use the center focus point and a split prism (Katz eyes) with a slow max aperture lens say >f/3.5, you will have a lot of issues with metering. I found this out with my K10D. In other words, when using this feature the camera does treat the focus point as a quasi spot meter. Using a spot meter mode with a Katz eye prism and a slow lens will cause metering errors. In my case, it was significant > 2 stops over exposure. This feature would be handy say if you were taking a portrait and the model was in the light and the rest of the background was dark and s/he was off center and you wanted to frame the shot and then move the focus point over the model. Of course, you could spot meter with the center point and then recompose, too.