DPFranz
Senior Member
An important question here, though, in the case of focus-and-recompose:The way I understand it, matrix metering on Nikon cameras is "smarter" than just averaging across the frame. There is an actual database of photo metadata (tens of thousands of records) against which the current photo is compared. Nikon cameras also consider the selected focus point during the evaluation process to ensure the item you've selected to focus on (presumably, the main subject of your photo) is given due consideration in calculating the final exposure.I was reading on Thom Hogan's site that the D80 (I think that was the one) did this preferential treatment of the content under the active focus sensor when using matrix metering, and he noted that this was largely a detractor of the appeal of that camera...too hard to use in practice.In my opinion the first shot is correctly exposed for the main subject or at the most a third of a stop too hot. The matrix metering in the D3/D700 is EXTREMELY sensitive to the content under the focus bracket in use. In this case if you were using the central bracket it did what it was asked to do.
Now, I can see how this would be beneficial in some cases, but this makes it more like center weighting, and I certainly don't want to have to change the active focus sensor on the fly in order to get a good reading - I can use center weighting and lock exposure, then recompose if I want that, but what I use matrix for (and what the D2x seems to do) is when I want a reasonable average exposure for the entire frame. I thought, indeed, that that was the purpose of matrix...otherwise what is the difference between matrix and center-weighted...matrix just has a larger "center" region?
Does the camera emphasize the content that was under the active focus center during focusing, or the content that is under the active focus center at the time of shutter release? My experience says that it is the latter, and I think I prefer it that way (meter based on the framing at the time of shutter release).
For example, using matrix metering, if I focus on a very bright part of scene (no AE-lock), then recompose and fire a shot, then focus on a very dark part of the scene and recompose to the identical framing as in the first shot, and fire a second shot, my experience seems to tell me that the exposures will be identical, or at least very similar, the only difference being if different parts of the image have changed to or from soft focus from sharp focus. For the sake of argument, assume everything in the frame is within the depth of field. Then there should be no difference between the exposures. Correct?
--
Dana Paul Franz
[email protected]
http://dfranz.smugmug.com
'The moment an emotion or fact is transformed into a photograph it is no longer a fact but an opinion .... All photographs are accurate. None of them is the truth.' - Richard Avedon