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Sensor resolution, any sites with actual measurements?

 
 
Neil Ellwood
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      03-06-2006
On Mon, 06 Mar 2006 09:03:10 -0600, Don Stauffer wrote:

> Neil Ellwood wrote:
>
>>>
>>>Why can't they design WA lenses with corner to corner sharpness (even
>>>wide open)?

>>
>> Ask a lens designer - they will probably tell you that it is a combination
>> of physics, engineering tolerances and available glass specifications.
>>

> As a one time lens designer, I'll take a poke at this. It is the physics
> and glasses, not tolerances.

When the engineers make the lens mounts they have to work with tolerances
as the perfect part connot be made, it can always be improved.>
> In many cases lens design is a situation of solving a set of equations
> with more variables than the number of equations- not enough degrees of
> freedom.
>
> Lens coatings only work well over a narrow range of angles.


--
Neil
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Dave Martindale
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      03-08-2006
Alfred Molon <(E-Mail Removed)> writes:

>Where do you get this 70%? If a pattern with n white lines and n black
>lines falls exactly on the lines of the CCD, so that each CCD line sees
>either a black line or a white line, the CCD will have a resolution of
>100% of the nominal pixel count. Maximum MTF. On the other hand if each
>CCD line sees half of a black line and half of a white line, the CCD
>will see a uniform gray (zero MTF).


Yes, and this situation is bad - whether you get black/white bars or
grey depends on the micro-level alignment of the image with the sensor.
Or if the spacing of the bars in the image is almost but not quite equal
to the pixel pitch, the image will alternate between black/white and
grey. Either way, it's bad news for the image.

To avoid this problem, most camera manufacturers include an
anti-aliasing filter. This is designed so that the camera *always*
shows grey for an image pattern at (or very close to) the Nyquist
frequency.

As the frequency of the pattern drops below Nyquist, the AA filter
response rises *and* the ability of the sensor to image it without
artifacts improves. At 70 or 80% of Nyquist, there's good enough
contrast to resolve detail.

Dave
 
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