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Re: [OM] Circ Pols

Subject: Re: [OM] Circ Pols
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Wed, 02 Feb 2011 07:33:28 -0500
I agree with the metering accuracy of the A1.  It is exceptionally good 
as was my first digital, a small Nikon whose model number I forget.  But 
I never put a polarizer on either one.

BTW, where did you learn all these design details?

Chuck Norcutt


On 2/1/2011 7:38 PM, Ken Norton wrote:
> Well, the reason is that the A1's matrix mode algorithm uses the
> overall EV to determine scene type. If, for example, you are shooting
> in bright sunlight the camera understands that and will use that as a
> baseline for exposure determination. If you do a closeup of a white
> car with bright chrome, the camera will understand that it is being
> fooled by too bright of a subject and will fall back on its baseline
> exposure that is programmed in for bright sunlight.
>
> If you place a polarizer or ND filter on the lens, the camera is
> fooled by the lower EV value and no longer correctly understands the
> scene. When confronted by that same white car with bright chrome, the
> camera will end up underexposing the picture because the EV value is
> not interpreted correctly and will fall back on standard
> focus-point/surround evaluation and ultimately to just overall
> average.
>
> Minolta and Nikon use almost identical methods for 3D matrix metering.
> The difference between the A1 and the Nikons is the knowledge of the
> lens itself. The A1 understands distance as well as the actual
> characteristics of the lens. The lens characteristics are hard-coded
> into the algorithm. Nikon, in the (D)SLRs, will make use of the
> distance information in some lenses, but the EV is determined
> relatively.
>
> Except for that one nuance, I will say that the A1's auto-exposure
> metering is the best I've ever used in any camera. It really is that
> good. In all honesty, I think the ESP mode in the IS-3 did better than
> my E-1 too.
>
> AG
>
>> The A1 uses contrast detect autofocus as do other digital P&S.  In fact,
>> I think all cameras that can focus in live view mode must be using
>> contrast detect and would likely not be affected by linear polarizers
>> (other than cutting the amount of light they have to work with).  I
>> thought the A1 also measured exposure from the sensor as well so I don't
>> understand why that would screw up the matrix metering.
-- 
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