Austin,

Of all people I would not expect to be called Gary Larson by you. I am not 
making any leap and I will have to say that no I am right and you are wrong. If 
more pixels cover a face, then when you enlarge than image you will have more 
detail on that face. Its a simple fact. Its like finer grain film. It will show 
better detail. 

Yes I know you are an engineer for hire, so what. That does not mean your right 
all the time. All I can say is I was trying to be polite and explain things but 
you went on and twisted them up and then turned it around to make your point 
and minimize what I was saying. Not very nice Austin. 

Peter K


----- Original Message ----
From: Austin Franklin <[EMAIL PROTECTED]>
To: [email protected]
Sent: Thursday, June 21, 2007 7:59:44 PM
Subject: RE: EOS Pixels and silly questions

Hi Peter,

> OK. Here is what I am saying. On a 30D you have a sensor that
> is 22.5mm x 15mm with 8.2 million effective pixels.
> The total area of that sensor is 337.5 square mm.
>
> On a 5D you have a sensor that is 35.8mm x 23.9mm with 12.7
> effective pixels. The area of that sensor is larger at 855.62
> square mm. However,
> the 5D has an area that is 2.5 times greater than the 30D yet has
> only 55% more
> pixels. So the density is less.

That is the density on the sensor, and is obvious, but it has nothing to do
with the density on the image, which is what you were stating.  You
specifically said any specific area of the image (you specified "a" face)
would have more pixel "density" from the smaller sensor.  This is what is
incorrect.  The density of the sensor is really a moot point if all you are
talking about is density of the sensor.  If you are relating it to image
quality (not just raw pixel count), then it has significance.

> So if I have a small object in the image I would have more
> pixels covering that area of the image with a 30D or XTi than I
> would with a
> 5D.

It doesn't matter whether it's a small object or a large object.  The object
occupies the same percentage of the overall image in either case.  From what
I can tell, you are making a Gary Larson "and then magic happened" leap here
between pixel density at the sensor and how it relates to pixel density on
the image.

The two are entirely disconnected.  The number of pixels in the image is
unrelated to the size of the sensor, if the images are the "same" (as in,
contain the same image boundaries).  The sensor could have all 10M pixels in
a .01"x.01" area, or in a 1" x 1" area, the pixel density of the image from
both would be identical in equally framed images.

> Now I am not talking Dynamic Range,
> Noise reduction, or anything else other than pixel density. That
> is all I am
> saying.

Understood.

> The main benefit is that the pixels are physically larger on
> the 5D enabling it to offer improvements at higher ISOs, hence
> cleaner images. There
> is something called pixel pitch which is the size of the pixels
> on an image
> sensor.

<snip>

Er, yes.  You know I design this stuff for a living, so you know I know
this, and as you said, this wasn't what you were talking about, and doesn't
relate to the issue at hand..but if you're looking for agreement, your
understanding of this is correct.

We agree about the pixel density at the sensor, but disagree as to how that
translates into pixel density of the resultant image.  The image does not
care about the size of the sensor, it only matters how many pixels it has
(with respect to "pixel density" and the image).  That is where you have a
disconnect.

Regards,

Austin






 
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