My understanding is the extra pixels are in use, doing things like
setting automatic white balance, providing information to the image
processor chip to clean up the image, making last minute adjustments
to the light reading, etc.
Each raw processor uses its own curve for mapping the raw data. They
are going to look different, but it would not have any effect on the
pixel count.
Winsor
Long Beach, California, USA
On Feb 12, 2006, at 12:48 PM, Chuck Norcutt wrote:
> I hadn't thought about this until now but I've noticed for a long time
> that sensor specs (such as those shown on dpreview for the E-1) always
> show more pixels available than actually used. I used to think that
> perhaps there is an area on the outer perimeter where circuits
> might not
> be completed or bayer patterns might not be complete.
>
> However, looking at the E-1 specs on dpreview I see: 5.6 million total
> pixels (2738x2044), 5.1 million active pixels (2614x1966) and 4.9
> million output pixels (2560x1920). Looking at the numbers I think
> there
> are far too many pixels that aren't used to support my simple
> hypothesis. Something else is afoot and I know not what.
>
> But I have recently learned of one area where different software can
> produce quite different results from raw files. For example, it might
> be that the red channel on a particular chip tends to blow out before
> the green and blue channels. The manufacturers software may consider
> this to be an unrealiable pixel and call the entire pixel white by
> boosting the green and blue channels to max as well. They'd rather
> report the pixel as blown than report an inaccurate color. Other,
> more
> daring software may show the pixel as recorded or may attempt to be
> even
> smarter and interpolate a different value for the "blown" red channel
> and fill it in. I think this may be the reason that some raw
> conversion
> software is reported to be able to pull a bit more shadow or highlight
> detail than some other converter.
>
> Chuck Norcutt
>
>
>
> Richard Lovison wrote:
>
>> On 2/11/06, C.H.Ling <chling@xxxxxxxxxxxxx> wrote:
>>
>>>
>>> Just done know why they don't use the maximum size, it
>>> gives more FOV.
>>
>>
>>
>> That's what I feel as well but then maybe the "cites" in the outer
>> rows and
>> columns vary in quality from chip to chip and the safe way for Oly
>> would be
>> to ignore them in the conversion.
>
>
>
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