Semi-Advanced Metering Question - DPChallenge Forums

Nikon AF Nikkor 85mm f/1.8D

10/04/2006 04:46:30 PM · #1

I have been reading about metering and exposure compensation etc. My question is this: When you set your camera to a particular focus point within a frame (in Canon speak this is â��manually selecting an AF pointâ��), do partial and center-weighted metering modes consider the selected AF point as the â��centerâ�� around which they meter â�� or is the camera still metering in the absolute center of the frame without reference to your AF point selection?

Here is an example: Letâ��s say that I am shooting for birds with a 300mm tele. I have set the camera to use the left-middle AF point exclusively. I have set the metering mode to partial because I only want to meter light in the portion of the frame on or around the bird (and the bird in this example is not nearly filling the frame). Will this work? When I focus on the bird using the left-middle AF point â�� will it consider the left-middle of the frame to be the â��centerâ�� around which it meters?

Any insight would be lovely,
Cheers.

LERtastic

Nikon D200

10/04/2006 04:52:57 PM · #2

interested to find out as well...

Kaveran

Canon EOS-50D

Canon EF 24-70mm f/2.8L USM

10/04/2006 05:06:54 PM · #3

Asfar as I know, Partial, spot and centerweighted are all based on the center of the viewfiender regardless of the AF point you chose to use.

Ecce_Signum

Canon EOS-5D Mark II

Canon EF 17-40mm f/4.0L USM

10/04/2006 05:20:29 PM · #4

Originally posted by Kaveran:

Asfar as I know, Partial, spot and centerweighted are all based on the center of the viewfiender regardless of the AF point you chose to use.

My thoughts exactly, a good question.

jdannels

Nikon D300s

Sigma 30mm f/1.4 EX DC HSM for Nikon

10/04/2006 05:35:18 PM · #5

a good question. I don't know for sure but have you tried out what you wanted to do and see if it changed? I mean maybe try puttin the camera on partial or spot metering and shoot in a doorway with a bright light on the otherside. And setup your camera so focus points are in different lighting conditions. Try metering with the center first and see what reading you get. Then change the focus point to the lighted side of the door and see if the exposure changes. Try one more with your focus completely in the shadow of the door. These exposure settings should be really different. A tripod might help to keep you from moving the center of the camera to see if there are changes. If I get a chance later I might try this, but I don't know if Nikon and Canon do this differently. just a thought.
joe

David.C

Nikon AF Nikkor 50mm f/1.8D

10/05/2006 03:43:31 AM · #6

From the manual for my D70 (page 75):

Spot: Camera meters circle 2.3mm (0.09") in diameter (approximately 1% of frame). Circle is centered on current fucus area, making it possible to meter off-center subjects ...

But that's for my Nikon, your millage may vary with those other guys.

BTW: This is only for spot metering, center-weighted always used the center of the frame. Again, I can't speak of other cameras.

Glad your finding the Exposure threads useful.

David

Canon EF 24-70mm f/2.8L USM

10/05/2006 08:40:49 AM · #7

Yes, thank you David(C) for posting the link to those exposure threads. I hope that it turns out that my canon's patial metering works as your Nikon. My guess is that my guess is that it does - I have shot enough under those exact circumstances to think it working properly. And I still think that center-weighted should follow point of focus if spot focus is on. Anyway I have not had time to test it.

Still looking for a Canon-toting expert here...

Kaveran

Canon EOS-50D

10/05/2006 09:54:46 AM · #8

From the canon 30D manual......

Partial Metering
"Partial metering covers about 9% of the viewfinder area at the center."

Spot Metering
"The metering is weighted at the center covering about 3.5% of the viewfinder area"

Center Weighted
"The metering is weighted at the center and then averaged for the entire scene"

Canon EF 24-70mm f/2.8L USM

10/05/2006 10:54:45 AM · #9

Yes, it looks like bad news for Canon 350D. I also note from my manual that AE Lock will lock on the CENTER AF POINT even if you have manually chosen some other AF point. This is true when using partial and center-weighted metering. Evaluative metering will actually use the selected AF point. I found this info in the reference section of the manual (on page 153).

So for 350D owners (and possibly other Canon owners as well), if you want to manually select an AF point, and you want to only meter light on that particular spot, you are better off using evaluative metering over partial metering. That is how it seems to me anyway.

elru21

Canon EOS-5D

10/05/2006 12:17:02 PM · #10

Originally posted by santaspores:

You could still use partial metering, you just have to meter with the center AF point over your particular spot and then AE lock or dial in your settings in maual, recompose with your selected AF point over your subject and then shoot.

Liza

Brad

Olympus OM-D E-M1

Olympus 40-150mm f/2.8 PRO M.Zuiko

10/05/2006 12:33:37 PM · #11

I tested this with my 350D using a building, bright street scene, darker wall on my right.
Selected AF point of far right. Used partial metering (center 9%) and held down the shutter 1/2 way and metered the wall, then metered the bright street. Recomposed, metering area in bright street, wall in far right AF point. Camera exposed for the street scene and AF system used the wall.
The AF and AE do not use the same points if off-center AF selected. The AE system is based on the center of the viewfinder and outward.

wavelength

Nikon D300

Nikon AF Nikkor 50mm f/1.8D

10/05/2006 12:41:09 PM · #12

Yeah, Canon has the High-ISO noiseless advantage. Nikon has the "spot metering moves with focus point" advantage.

I think the 1 series actually work the same as all Nikons on that end. (think, not know)