Film is different than sensors. Did you read the article?

----- Original Message ----
From: Austin Franklin <[EMAIL PROTECTED]>
To: [email protected]
Sent: Wednesday, June 20, 2007 3:30:39 PM
Subject: RE: EOS A slightly silly query

Hi Peter,

> No Austin. If you and I take an image and I use a 10MP sensor on
> say a Rebel XTi and that is half frame camera. And you use one
> with 12.7 that is full frame, and let us say we take the same
> exact image of a group of people. I will have more pixels
> covering a small face in the crowd than you will.

That's not right, and I would really like you to explain the math behind
that, because if you do, you'll find out it's wrong.

A 10mp APS camera taking the same framed image (meaning the images contain
the exact same boundaries/content) as a 12mp full frame camera, the 10mp APS
will not have more pixels per unit image area (the same face) than the 12.7,
the 12.7 will have slightly more.  The physical size of the sensor makes no
difference (the number of pixels do...though larger pixels do typically give
better image data, but that's got nothing to do with this discussion), if
the framing/image boundary/content, what ever you want to call it, is the
same.  If the sensor has the same number of pixels, no matter what it's
physical size, each pixel will represent the same area of the image, again,
if the image contains the exact same boundary/content.

Now with film, your statement would make sense.  Given a 645 vs a 35mm, the
645 will have higher film grain density for the same "image content" area.
But that is not true for digital.  In analog, film grain is basically
constant (enough) for any given film (say, Tri-X)...and therefore 645 has
far more grains than 35mm.  But with a 10M sensor vs a 10M sensor, size
doesn't matter if the image is the same.

You must be confusing your self with something else.  For instance, if you
have, say, a 10M full frame and a 10M APS with the same focal length at the
same distance from the subject, the 10M APS has a higher pixel density...but
the difference is there is now a magnification of 1.6...therefore the actual
image is different...you are zoomed in, and cutting off a significant amount
of the border that the full frame camera image contains.

Regards,

Austin






 
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