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Using fewer than a camera's maximum pixels

 
 
Tiffany S.
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      02-06-2006
I have a Canon 300D, which has different quality setting. The lower the
setting, the fewer pixels the pictures have.

Since the lens always covers all 6.1 megapixels, which of the following
happens when I take a low-quality picture?

1) Pictures are still taken with all 6.1 megapixels, but the camera's
software reduces the image size prior to storage.

2) The output from only one out of every three pixels gets saved.

3) Every three pixels are combined to act as one pixel. In this way,
even though resolution is less, the iso 1600 setting improves because it
has less noise.

 
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Dennis Pogson
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      02-06-2006
Tiffany S. wrote:
> I have a Canon 300D, which has different quality setting. The lower
> the setting, the fewer pixels the pictures have.
>
> Since the lens always covers all 6.1 megapixels, which of the
> following happens when I take a low-quality picture?
>
> 1) Pictures are still taken with all 6.1 megapixels, but the camera's
> software reduces the image size prior to storage.
>
> 2) The output from only one out of every three pixels gets saved.
>
> 3) Every three pixels are combined to act as one pixel. In this way,
> even though resolution is less, the iso 1600 setting improves because
> it has less noise.


You are confusing picture size with quality. Size produces a picture with a
known number of pixels, length and breadth, usually the software will offer
you 3 or more choices.

Quality determines the degree of jpeg compression the software applies to
the picture, the more compression, the lower the resolution/quality of the
finished picture.

That's how it works with most digital cameras, the Canon may be different,
but I doubt it.


 
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Jim
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      02-06-2006
I don't know for certain, however option 1 is the most logical. The other 2
don't seem a logical step.


"Tiffany S." <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> I have a Canon 300D, which has different quality setting. The lower the
> setting, the fewer pixels the pictures have.
>
> Since the lens always covers all 6.1 megapixels, which of the following
> happens when I take a low-quality picture?
>
> 1) Pictures are still taken with all 6.1 megapixels, but the camera's
> software reduces the image size prior to storage.
>
> 2) The output from only one out of every three pixels gets saved.
>
> 3) Every three pixels are combined to act as one pixel. In this way,
> even though resolution is less, the iso 1600 setting improves because it
> has less noise.
>



 
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Ben Brugman
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      02-06-2006
For the Canon 350 D there are three options for the resolution :

.. 3456 x 2304 (L)
.. 2496 x 1664 (M)
.. 1728 x 1152 (S)

The number of pixels is about 8 Mp.
How are the pixels organised.

G B
R G

Two greens, one bleu and one red for each for pixels.
There are 1728 x 1152 off these groups. (Exactly the amount of
the small resolution).

So for the Small resolution all pixels are used. Probably the greens
are averaged the red and blues are used as they are.
(Could be that the colors are shifted half a pixel in the algoritm but
to me this is not likely).
This algoritm is the most logical, because hardly any calculation has
to be done, and all information is used.

For the Medium resolution all pixels are used but a fairly complex
algoritm is used to get the number of 2496 x 1664 pixels. Most
pixels are interpolated from the surrounding pixels.

For the Large resolutios all pixels are used and extra information
is calculated to get the 3456 x 2304 resolution. this is a fairly
simple algoritm. This is because the number off result pixels
align with the number of sensor pixels.

I hope this anwsers your question and give you some extra insight.

ben brugman


"Tiffany S." <(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed)...
>I have a Canon 300D, which has different quality setting. The lower the
> setting, the fewer pixels the pictures have.
>
> Since the lens always covers all 6.1 megapixels, which of the following
> happens when I take a low-quality picture?
>
> 1) Pictures are still taken with all 6.1 megapixels, but the camera's
> software reduces the image size prior to storage.
>
> 2) The output from only one out of every three pixels gets saved.
>
> 3) Every three pixels are combined to act as one pixel. In this way,
> even though resolution is less, the iso 1600 setting improves because it
> has less noise.
>



 
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Done
Guest
Posts: n/a
 
      02-06-2006

"Ben Brugman" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> For the Canon 350 D there are three options for the resolution :
>
> . 3456 x 2304 (L)
> . 2496 x 1664 (M)
> . 1728 x 1152 (S)
>
> The number of pixels is about 8 Mp.
> How are the pixels organised.
>
> G B
> R G
>
> Two greens, one bleu and one red for each for pixels.
> There are 1728 x 1152 off these groups. (Exactly the amount of
> the small resolution).
>
> So for the Small resolution all pixels are used. Probably the greens
> are averaged the red and blues are used as they are.
> (Could be that the colors are shifted half a pixel in the algoritm but
> to me this is not likely)


Is the above certified fact, or speculation?


 
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Done
Guest
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      02-06-2006

"Jim" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
>I don't know for certain, however option 1 is the most logical. The other
>2
> don't seem a logical step.


Is that your impression, or fact?


 
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Bill Funk
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      02-06-2006
On Mon, 6 Feb 2006 14:27:11 -0500, http://www.velocityreviews.com/forums/(E-Mail Removed) (Tiffany S.)
wrote:

>I have a Canon 300D, which has different quality setting. The lower the
>setting, the fewer pixels the pictures have.
>
>Since the lens always covers all 6.1 megapixels, which of the following
>happens when I take a low-quality picture?
>
>1) Pictures are still taken with all 6.1 megapixels, but the camera's
>software reduces the image size prior to storage.
>
>2) The output from only one out of every three pixels gets saved.
>
>3) Every three pixels are combined to act as one pixel. In this way,
>even though resolution is less, the iso 1600 setting improves because it
>has less noise.


1) is right.
No speculation needed. Since the sensor has a Bayer filter, it's not
possible to get any quality by skipping any specified number of
pixels. Instead, the number of pixels is reduced by the firmware in
the camera. Simple resizing.

--
Bill Funk
replace "g" with "a"
 
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Ben Brugman
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      02-06-2006

>
> Is the above certified fact, or speculation?
>
>

It's based on knowledge, fairly common knowledge as wel.
Search the web for bayer pattern to learn more about this.
It's not based on self investigated proof.

ben brugman


 
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