How big is a pixel?

Different variants of this question seem to pop up in this group at
regular intervals.

In a hope of reducing the bandwidth wasted on this subject, I've
created the "How big is a pixel?"-FAQ, where these thing are
explained in a way that is accessible (I hope) to thoe starting
out with digital photography:

The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Comments and corrections are welcome.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
================================================== ======================
«To live outside the law, you must be honest.» (Bob Dylan)

Gisle Hannemyr wrote:
[]
The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Comments and corrections are welcome.

A useful start....

Cheers,
David

Gisle Hannemyr wrote:
[]
The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Comments and corrections are welcome.

A useful start....

Cheers,
David

Nice explanation--I like the rest of your site too.

Nice explanation--I like the rest of your site too.

Bt the answer is so simple - a pixel is this big - no less and certainly no
more.

--
http://www.chapelhillnoir.com
home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html

"Gisle Hannemyr" wrote in message
...
Different variants of this question seem to pop up in this group at
regular intervals.

In a hope of reducing the bandwidth wasted on this subject, I've
created the "How big is a pixel?"-FAQ, where these thing are
explained in a way that is accessible (I hope) to thoe starting
out with digital photography:

The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Comments and corrections are welcome.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
================================================== ======================
«To live outside the law, you must be honest.» (Bob Dylan)

Bt the answer is so simple - a pixel is this big - no less and certainly no
more.

--
http://www.chapelhillnoir.com
home of The Camera-ist's Manifesto
The Improved Links Pages are at
http://www.chapelhillnoir.com/links/mlinks00.html
A sample chapter from "Haight-Ashbury" is at
http://www.chapelhillnoir.com/writ/hait/hatitl.html

"Gisle Hannemyr" wrote in message
...
Different variants of this question seem to pop up in this group at
regular intervals.

In a hope of reducing the bandwidth wasted on this subject, I've
created the "How big is a pixel?"-FAQ, where these thing are
explained in a way that is accessible (I hope) to thoe starting
out with digital photography:

The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Comments and corrections are welcome.
--
- gisle hannemyr [ gisle{at}hannemyr.no - http://folk.uio.no/gisle/ ]
================================================== ======================
«To live outside the law, you must be honest.» (Bob Dylan)

"Gisle Hannemyr" wrote in message
...
SNIP
The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Good initiative.

Comments and corrections are welcome.

You are brave ;-)

Q1 "The resolution of a digital image in itself is expressed in
pixels".
This already causes part of the confusion, and I had hoped to see it
phrased differently (in fact I wouldn't mention the word resolution in
relation to the amount of pixels at all).

"Resolution" (the possibility to resolve/separate fine details that
are positioned close to each other) is expressed by industry/science
as cycles/mm (or in some cases as angular resolution if that makes
more sense for the application). The moment you express it as numbers
of pixels, the confusion starts because pixels aren't created equal.
In fact, their quantity has little to do with it.

Pixels are the quantized result of point samples or area samples, and
it is the sampling density that defines the upper limit of the
intrinsic resolution they can represent (which is unrelated to the
size of the pixel, because that is undetermined until related to a
physical medium).

Bart

"Gisle Hannemyr" wrote in message
...
SNIP
The FAQ is located at:
http://heim.ifi.uio.no/~gisle/photo/pixels.html

Good initiative.

Comments and corrections are welcome.

You are brave ;-)

Q1 "The resolution of a digital image in itself is expressed in
pixels".
This already causes part of the confusion, and I had hoped to see it
phrased differently (in fact I wouldn't mention the word resolution in
relation to the amount of pixels at all).

"Resolution" (the possibility to resolve/separate fine details that
are positioned close to each other) is expressed by industry/science
as cycles/mm (or in some cases as angular resolution if that makes
more sense for the application). The moment you express it as numbers
of pixels, the confusion starts because pixels aren't created equal.
In fact, their quantity has little to do with it.

Pixels are the quantized result of point samples or area samples, and
it is the sampling density that defines the upper limit of the
intrinsic resolution they can represent (which is unrelated to the
size of the pixel, because that is undetermined until related to a
physical medium).

Bart

Tony wrote:

Bt the answer is so simple - a pixel is this big - no less and certainly no
more.


Hi...

Given the confusion around this issue, I decided to
resolve it for once and for all.

No expense was spared. 10's of 1000's of man-hours
invested. Only the highest calibre of test equipment.
Calibrated against NASA's American equipment. Double
checked against England's atomic clock. Temperature
controlled. Humidity controlled. Ambient light
controlled. Zero room for error.

Our undisputable findings are that a pixel is:

Precisely one pixel wide.
Precisely one pixel high.

And for those printing 3 dimensional photos, it's
also precisely one pixel deep. Unless stepped on.

Ken