As I said, use your histogram and bias it for the error in the E-1.
Chuck Norcutt
On 9/7/2011 11:54 AM, Ken Norton wrote:
>> I went and double-checked the setting, and I have it at centre-weighted
>> averaging. I set it up this way after getting the E-500 so that it would
> be
>> similar to the OM-1 metering, which I had become used to.
>
> Interesting! This brings up an oddity that I've noticed, but haven't given
> much thought to. It seems that if there is a bright spot of light in the
> scene, the averaging meter will get overly driven down. Where averaging
> normally takes into account and "averages" the entire pattern area, with my
> E-1 and DMC-L1, the image will frequently underexpose. For example, if I
> photograph an automobile, but the sun is reflecting off of a bit of chrome,
> the picture underexposes. In ESP mode, it does find. With the OM series, it
> does fine.
>
> Here is my theory--take it strictly as a theory being submitted for peer
> review:
>
> 1. Traditional center-weight metering system uses a single sensor
> (detector). The pattern is of a single coverage zone and does not use any
> segments to isolate portions of the zone out for other purposes. It is an
> "averaging" meter in every sense of the word in that it averages the
> brightness values of all light falling in that zone to come up with the EV.
> In digital camera terms, it's a one-pixel camera. If half the scene was
> black and half was white, the sensor would only know of the combined values
> which average to a gray. It can't see the black or the white, only the mixed
> light.
>
> 2. Modern metering systems use a multi-zone detector with multiple "pixels".
> This is frequently combined with the AF sensor to get another pinpoint
> source of light measurement. So, to achieve an "average" exposure for
> "center-weight averaging", the camera combines the values from all pixels
> (detectors) within the coverage pattern. In my black/white scene, some of
> the detectors see black, some see white and the ones at the transition point
> average them together.
>
> 3. Multi-segment detectors in modern cameras are weighted in the mix-matrix
> per the size in proportion to the whole of the coverage pattern. If there
> are three detectors (left surround, center spot, right surround), the
> camera's fuzzy logic will mix the values of the three detectors together
> based on the percentage of the area of coverage. If the left surround is 40%
> of the total, right surround is 40% of the total, the center spot is 10% of
> the total.
>
> 4. When one of the surrounds (in my 3-detector array) encounters a bright
> object (chrome reflecting the sun), it will drive the exposure value of that
> particular detector up high. Inotherwords, the average EV of that particular
> segment is far higher than the average EV of the entire scene.
>
> 5. As the fuzzy logic averages the EV of all detectors together based on the
> percentage of coverage area for each detector, the surround, which may have
> 40% of the coverage will be heavily weighted in the overall average.
>
> 6. What this will do is swing the center-weight averaging EV value too far
> in one direction as it isn't a true averaging of the entire coverage zone,
> but an averaging of the average EV of each detector's coverage areas.
>
> 7. Cameras with far more detector segments than three will combine the EV
> values in a manner which a computer programmer wrote the code. Most of the
> work is devoted to ESP or Matrix metering, little regard is given to
> center-weight averaging. It is possible that an engineering flaw in the way
> the detectors are averaged is present in the camera. This is probably a
> given, because Olympus had stated how the ESP metering in the E-3 was
> revised and updated.
>
> Dr. Schnozz
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