That is correct, there will be no resolution loss if you use a K20D
with a shorter lens and crop down to the equivalent of the K10D with
the longer lens. Sensor size does not determine resolution at all
(unlike with film). Pixel density does. A 3000x2000 pixel sensor
delivers the same resolution if it's 30x20mm as it does if its
30x20cm.

This of course assumes that the lens is not limiting the resolution of
the image. And of course that the AA filter on both is similar (AA
filters reduce the detail resolution abilities of a sensor to prevent
moire).

The advantages of a larger sensor(more truly larger sensor sites at a
given pixel count) are better noise performance, better dynamic range
and shallower DoF effects.

-Adam

On Fri, Jun 27, 2008 at 8:18 AM, J. C. O'Connell <[EMAIL PROTECTED]> wrote:
> Are you trying to say that there will be no resolution loss in using a K20D
> with a shorter lens vs a K10D with a longer lens if the AOV of the image
> is kept the same via cropping the K20D image? The REAL sensor size of the 2
> cameras
> are NOT EQUIVALENT if you crop the K20D image and use a shorter fl lens.
>
> JC OCONNELL
> [EMAIL PROTECTED]
>
>
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of
> Anthony Farr
> Sent: Friday, June 27, 2008 8:03 AM
> To: 'Pentax-Discuss Mail List'
> Subject: RE: Sensor resolution V focal length..........
>
>
> The crop will be the same from K10d to K20d, because the crop factor is
> related to the sensor dimension not its resolution, and the two cameras have
> equivalent sensor dimensions.
>
> The K20D shots will "enlarge" more at 100% view, simply because it has a
> greater pixel density.  This doesn't mean anything other than that your
> monitor resolution (e.g. 1024 x 768)represents a smaller patch of the K20ds
> sensor compared to the K10d.  The >>whole<< picture will have the same field
> of view for the same lens when the two camera models are compared.  You
> wouldn't print at 100%, the only practical use for this view is when
> performing some editing functions, and for pixel peeping.
>
> Regards,
> Anthony Farr
>
>> -----Original Message-----
>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf
>> Of John Wittingham
>> Sent: Friday, 27 June 2008 8:59 PM
>> To: [email protected]
>> Subject: Sensor resolution V focal length..........
>>
>> I'm in need of some longer glass, longer than 300mm. It occured to me
>> the
> other
>> day that the crop of a given area of a frame would be consirerably
>> bigger
> the more
>> resolution you have from the sensor of the camera viewed at 100%. So
>> I'm
> thinking
>> 400mm on the K10D would be approximately 33% bigger at the same crop
>> as it would be from 300mm viewed at 100% right?
>>
>> So if I'm using a K20D how much bigger would a crop of the same
>> subject
> shot with
>> the K10D be viewed at 100%, could I substitute pixels for focal length
> providing the
>> lens resolution is up to the job? Are there any downsides other than
>> the
> obvious
>> differences when using a shorter focal length such as DoF?
>>
>> Regards,
>>
>> John
>>
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-- 
M. Adam Maas
http://www.mawz.ca
Explorations of the City Around Us.

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