On Oct 22, 2006, at 8:24 AM, Shel Belinkoff wrote: > ...While it might have been nice to know how to make the lenses > provide multi > segment metering, I really didn't care very much to waste time > looking for > a solution. Others here are so much better at fiddling around with > such > things. If it were an issue, I'd have just asked the list, and > guys like > Roberts would probably have an answer. > > BTW, isn't matrix metering what Nikon calls their system, and doesn't > Pentax use the term "multi segment metering?" Are the two the > same, or is > there some difference between them? ...
Nikon was the first to market with "matrix metering" in the FA model and I guess the name is theirs, but it's stuck around as being a generic term. Pentax calls it 'multi-segment metering'. Both are implementations of the same idea, which I think is more precisely called "evaluative exposure estimation": - Measure the scene at multiple points using independently sensitive zones. - Compare the relationships of the zones, weighted appropriately, against a library of scene types to identify known exposure evaluation issues. - Take that type analysis plus the total average brightness of the scene, along with the weighted segment values, to produce a good guess at best overall exposure setting. For the simple, early generation systems like this, the information required for open aperture metering is max aperture and exposure time aperture setting. This can become arbitrarily trickier with more sophisticated information and higher power processing in the metering system. Factors that help aid scene type identification can be focal length and focus setting, factors that help aid exposure setting can be color balance, you can include color information (as Nikon does with RGB matrix metering bodies). These later systems require lenses that provide the relevant additional information for the specific metering system in question. Ancient lenses that do not have chips in them to provide this information electronically are not compatible with this metering mode on the Pentax DSLRs no matter what you do, due to the way the implementation was integrated with the rest of the camera's real time control system. (The same is true for Nikon's D200 ... except that they've provided a way to input some of the required data for a specific lens that you mount and enable one of the simpler forms of the metering mode.) In my experience, matrix metering evaluations with the Pentax *ist DS resolve to be arbitrarily close to Center Weighted Averaging readings UNLESS I set the option to link the AF and AE point and use the full AF sensor array. Then I see some variations in the selected exposure settings. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
