Thanks. Very interesting stuff!
Chuck Norcutt
On 4/12/2011 5:34 PM, Ken Norton wrote:
> Chuck, that slot-canyon question is a good one. I do not know the
> answer about the Nikon or the 5D, but I do know that my E-1 and DMC-L1
> will choke the choke of death on getting the right exposure.
>
> The A1 would have a fighting chance, depending on where it determines
> the point of focus to be. If the matrix determines the bright center
> to be the subject it will do what it wants to do to protect it.
> However, only if the AF doesn't determine that a darker object is
> closer and then it will boost the exposure for it and blow out the
> highlights.
>
> Personally, I'd put my luck on the OM-3/4 Multispot metering combined
> with a healthy dose of understanding of the "Zone System".
>
> Back to the A1 for a second, since I actually have it with me right
> here. Using the Spot AE to measure maximum differential, between a
> white subject and a deeply shadowed subject at my cubical, it measured
> 7 stops. So, a little test of the metering methods:
>
> Using Matrix and AF, but with manual selection point to force the
> focus point around (defeating the system from trying to find the
> closest subject--this is a viable and repeatable test and perfectly
> correct with the A1), the camera is giving me a maximum exposure
> variance of 1.3 stops. It is biasing the exposure just enough to make
> the dark subject a bit lighter, but not so much that it becomes
> mid-tone. On the other hand, when the AF spot is moved to the white
> subject, (same composition), it biases the exposure downward just
> enough to make the white subject fall entirely within the sensor's
> tolerance, but not so much that the shadows block out. In this test of
> a 7 stop subject brightness variance, it limited the exposure range to
> 1.3 stops.
>
> Using Averaging Mode, with the same exact settings and procedures, the
> exposure remained the same unless I moved the camera changing the
> overall brightness level of the entire scene. But depending on where I
> pointed the camera, it skewed as much as 3.0 stops. I repeated the
> Matrix test copying the camera movements of Averaging and the exposure
> would not budge--it remained 1.3 stops maximum shift depending on
> where the focus point was pointed.
>
> Using Spot Mode, we get 7 stops of variability depending on where it
> is pointed--same as using AEL-Spot.
>
> OK, so the OM-3Ti is also sitting here. Due to the differences in spot
> metering and lens technology there is some change. The OM-3Ti with
> 50/1.4 is giving me 6 stops of spread, the 35-80/2.8 is showing 6.6
> stops of spread.
>
> The Sekonic L-508 isn't even sensitive enough to give me a good
> reading of the dark region, but the most it would show me was six
> stops and I had to substitute a subject one stop lighter to get it, so
> I'm calling it about seven stops, give or take some change.
>
> AG
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