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peak to peak vs rms noise in images.

 
 
jpc
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      04-01-2004
I was taking line profiles of blue sky noise in two images--an 8080
image posted recently and 3020 image from my camera.

If I ratioed the peak to peak variation --11levels for the 8080 and 5
for the 3020, I can say the 8080 is 2.2 times more noisy than my
camera.

If I ratio the standard deviations-- the rms noise- I get 1.6 or
roughly the square root of 2.2.

In electrical engineer parlance I believe the first ratio is the
equivent of the variations in the voltage while the second is the
variations in the power, and power noise is normally used as the
standard.

In visual terms I'd think it should be the other way around. We see
differences in pixel intensity not pixel power intensity. By that
standard the 8080 is 2.2 times more noisy than my camera.

Anyone have a different opinion?

jpc


 
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Canongirly
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      04-01-2004

<jpc> wrote in message news:(E-Mail Removed)...
> I was taking line profiles of blue sky noise in two images--an 8080
> image posted recently and 3020 image from my camera.
>
> If I ratioed the peak to peak variation --11levels for the 8080 and 5
>

SNIP

> Anyone have a different opinion?
>

Just one? What the hell are you talking about?
 
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Charlie Ih
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      04-01-2004
I try to answer the original question. The gray levels on the photo
(digital or film) are produced by photo energy (which is power x time).
When you read out the voltage (or current) from the photo, the
voltages represent the original photo or noise power. In my opinion,
you don't need to do square root again.


In article <406c3fb1$(E-Mail Removed)>,
Canongirly <(E-Mail Removed)> wrote:
>
><jpc> wrote in message news:(E-Mail Removed)...
>> I was taking line profiles of blue sky noise in two images--an 8080
>> image posted recently and 3020 image from my camera.
>>
>> If I ratioed the peak to peak variation --11levels for the 8080 and 5
>>

>SNIP
>
>> Anyone have a different opinion?
>>

>Just one? What the hell are you talking about?



--
Charles S. Ih
302-831-8173, FAX 302-831-4316
 
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DavidG
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      04-02-2004
jpc <> wrote in message news:<(E-Mail Removed)>. ..
> I was taking line profiles of blue sky noise in two images--an 8080
> image posted recently and 3020 image from my camera.
>
> If I ratioed the peak to peak variation --11levels for the 8080 and 5
> for the 3020, I can say the 8080 is 2.2 times more noisy than my
> camera.
>
> If I ratio the standard deviations-- the rms noise- I get 1.6 or
> roughly the square root of 2.2.
>
> In electrical engineer parlance I believe the first ratio is the
> equivent of the variations in the voltage while the second is the
> variations in the power, and power noise is normally used as the
> standard.


You are interpreting your results incorrectly. The relationship
between P-t-P and RMS noise is not one of voltage vs. power. The keys
is that the "R" in
RMS stands for root. Thus, both measurements are in the same units.
P-t-P measures maximum excursions, including the rare "tails" of the
random distribution describing the noise. RMS describes a type of
average. The result is a number which, *if* squared, would give you a
power equal to the average power.

Using your voltage analogy, and with a sine wave that varies between
-1V and 1V, the peak-to-peak measurement would be 2V and the RMS would
be 0.707 or sqrt(2)/2 V.

David
 
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Don Stauffer
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      04-02-2004
The 2.2 to 1 ratio of p-p to rms only applies to sinusoidal waveforms.
Noise in a camera is not sinusoidal, so do not expect that ratio to
work. The noise is likely to be a form of Poisson distribution.

jpc wrote:
>
> I was taking line profiles of blue sky noise in two images--an 8080
> image posted recently and 3020 image from my camera.
>
> If I ratioed the peak to peak variation --11levels for the 8080 and 5
> for the 3020, I can say the 8080 is 2.2 times more noisy than my
> camera.
>
> If I ratio the standard deviations-- the rms noise- I get 1.6 or
> roughly the square root of 2.2.
>
> In electrical engineer parlance I believe the first ratio is the
> equivent of the variations in the voltage while the second is the
> variations in the power, and power noise is normally used as the
> standard.
>
> In visual terms I'd think it should be the other way around. We see
> differences in pixel intensity not pixel power intensity. By that
> standard the 8080 is 2.2 times more noisy than my camera.
>
> Anyone have a different opinion?
>
> jpc


--
Don Stauffer in Minnesota
http://www.velocityreviews.com/forums/(E-Mail Removed)
webpage- http://www.usfamily.net/web/stauffer
 
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DJ
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      04-03-2004
On Thu, 01 Apr 2004 09:20:24 -0600, jpc <> wrote:

>I was taking line profiles of blue sky noise in two images--an 8080
>image posted recently and 3020 image from my camera.
>
>If I ratioed the peak to peak variation --11levels for the 8080 and 5
>for the 3020, I can say the 8080 is 2.2 times more noisy than my
>camera.
>
>If I ratio the standard deviations-- the rms noise- I get 1.6 or
>roughly the square root of 2.2.
>
>In electrical engineer parlance I believe the first ratio is the
>equivent of the variations in the voltage while the second is the
>variations in the power, and power noise is normally used as the
>standard.
>
>In visual terms I'd think it should be the other way around. We see
>differences in pixel intensity not pixel power intensity. By that
>standard the 8080 is 2.2 times more noisy than my camera.
>
>Anyone have a different opinion?
>
>jpc
>


Unlike some, I shall refrain from lecturing you on the math of rms vs pp. I
think you know all that.

I think the answer to your musing is that "it depends". Probably no-one has done
any research on the *subjective* perception of image noise. That would require a
large number of tests with many people observing many pictures and scoring them
wrt noise. I suspect if such work was done the outcome would be a pink
noise/white noise equivalent weighting that takes into account such matters as
spatial bandwidth, the colouration of the noise, the amount of image detail etc.
In other words, the rms vs pp vs whatever other measures question can't be
resolved.

It's an exact equivalent to the grain debate. There's nice grain and ugly grain.
People used to argue interminably Tri-X grain versus HP3 grain or whatever, or
the grain produced by one developer or the other, or at 20'C versus 25'C.

As to the two cameras you compared. The ratio is 1.6:1 or 2.2:1. Either way I'd
say "about twice as much". Anything else is measurebation.

 
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Rescho
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      04-03-2004
I often wonder why digital still camera noise levels aren't quoted in
decibels (db) as in other type of electronic signal devices? For example a
good broadcast television camera's signal to noise ratio (the rms noise
level relative to a signal voltage at peak white) would be (say) 50 db and
would be better by a voltage factor of two than a camera with a signal to
noise ratio of 44db (under the same conditions). Using this system we would
have precise and easily measurable noise figures with which to objectively
compare cameras.

The electronics industries have used this method of noise measurement for
the last 80 odd years in all kinds of signal transducers (TV cameras,
microphones, record players, telephones etc.) and processing circuitry
(amplifiers, transmitters, telephone lines etc.). There is no reason (that
I can see) why this method shouldn't be used for digital still cameras.

Why has this time proven method been ignored by the digital photography
industry?

Regards
Rescho

"DJ" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Thu, 01 Apr 2004 09:20:24 -0600, jpc <> wrote:
>
> >I was taking line profiles of blue sky noise in two images--an 8080
> >image posted recently and 3020 image from my camera.
> >
> >If I ratioed the peak to peak variation --11levels for the 8080 and 5
> >for the 3020, I can say the 8080 is 2.2 times more noisy than my
> >camera.
> >
> >If I ratio the standard deviations-- the rms noise- I get 1.6 or
> >roughly the square root of 2.2.
> >
> >In electrical engineer parlance I believe the first ratio is the
> >equivent of the variations in the voltage while the second is the
> >variations in the power, and power noise is normally used as the
> >standard.
> >
> >In visual terms I'd think it should be the other way around. We see
> >differences in pixel intensity not pixel power intensity. By that
> >standard the 8080 is 2.2 times more noisy than my camera.
> >
> >Anyone have a different opinion?
> >
> >jpc
> >

>
> Unlike some, I shall refrain from lecturing you on the math of rms vs pp.

I
> think you know all that.
>
> I think the answer to your musing is that "it depends". Probably no-one

has done
> any research on the *subjective* perception of image noise. That would

require a
> large number of tests with many people observing many pictures and scoring

them
> wrt noise. I suspect if such work was done the outcome would be a pink
> noise/white noise equivalent weighting that takes into account such

matters as
> spatial bandwidth, the colouration of the noise, the amount of image

detail etc.
> In other words, the rms vs pp vs whatever other measures question can't be
> resolved.
>
> It's an exact equivalent to the grain debate. There's nice grain and ugly

grain.
> People used to argue interminably Tri-X grain versus HP3 grain or

whatever, or
> the grain produced by one developer or the other, or at 20'C versus 25'C.
>
> As to the two cameras you compared. The ratio is 1.6:1 or 2.2:1. Either

way I'd
> say "about twice as much". Anything else is measurebation.
>





 
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John Navas
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Posts: n/a
 
      04-03-2004
[POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

In <406e3512$0$12740$(E-Mail Removed)> on Sat, 3 Apr 2004
13:52:25 +1000, "Rescho" <(E-Mail Removed)> wrote:

>I often wonder why digital still camera noise levels aren't quoted in
>decibels (db) as in other type of electronic signal devices? For example a
>good broadcast television camera's signal to noise ratio (the rms noise
>level relative to a signal voltage at peak white) would be (say) 50 db and
>would be better by a voltage factor of two than a camera with a signal to
>noise ratio of 44db (under the same conditions). Using this system we would
>have precise and easily measurable noise figures with which to objectively
>compare cameras.
>
>The electronics industries have used this method of noise measurement for
>the last 80 odd years in all kinds of signal transducers (TV cameras,
>microphones, record players, telephones etc.) and processing circuitry
>(amplifiers, transmitters, telephone lines etc.). There is no reason (that
>I can see) why this method shouldn't be used for digital still cameras.
>
>Why has this time proven method been ignored by the digital photography
>industry?


Perhaps because of the common use of noise reduction, which makes any such
spec problematic.

--
Best regards,
John Navas
[PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
<http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]
 
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Rescho
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      04-03-2004
> Perhaps because of the common use of noise reduction, which makes any such
> spec problematic.

If you are referring to "in camera" noise reduction then that would be
included in the s/n figure for the camera and used when evaluating the
camera. If you are referring to post camera noise reduction the I can't see
that it's relevant. For example, with my previous camera (Minolta 7i) I had
to use noise reduction to improve images taken at (say) 400 ISO, now with my
Canon 300D, the noise levels are usually acceptable without post camera
noise processing at the same ISO setting. This is because the Canon has a
better s/n ratio in the first place.

Regards
Rescho.

"John Navas" <(E-Mail Removed)> wrote in message
newsLqbc.3561$(E-Mail Removed)...
> [POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]
>
> In <406e3512$0$12740$(E-Mail Removed)> on Sat, 3 Apr 2004
> 13:52:25 +1000, "Rescho" <(E-Mail Removed)> wrote:
>
> >I often wonder why digital still camera noise levels aren't quoted in
> >decibels (db) as in other type of electronic signal devices? For example

a
> >good broadcast television camera's signal to noise ratio (the rms noise
> >level relative to a signal voltage at peak white) would be (say) 50 db

and
> >would be better by a voltage factor of two than a camera with a signal to
> >noise ratio of 44db (under the same conditions). Using this system we

would
> >have precise and easily measurable noise figures with which to

objectively
> >compare cameras.
> >
> >The electronics industries have used this method of noise measurement for
> >the last 80 odd years in all kinds of signal transducers (TV cameras,
> >microphones, record players, telephones etc.) and processing circuitry
> >(amplifiers, transmitters, telephone lines etc.). There is no reason

(that
> >I can see) why this method shouldn't be used for digital still cameras.
> >
> >Why has this time proven method been ignored by the digital photography
> >industry?

>
> Perhaps because of the common use of noise reduction, which makes any such
> spec problematic.
>
> --
> Best regards,
> John Navas
> [PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
> <http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]



 
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John Navas
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      04-03-2004
[POSTED TO rec.photo.digital - REPLY ON USENET PLEASE]

In <406e3f5a$0$439$(E-Mail Removed)> on Sat, 3 Apr 2004 14:35:52
+1000, "Rescho" <(E-Mail Removed)> wrote:

>> Perhaps because of the common use of noise reduction, which makes any such
>> spec problematic.


>If you are referring to "in camera" noise reduction then that would be
>included in the s/n figure for the camera and used when evaluating the
>camera. If you are referring to post camera noise reduction the I can't see
>that it's relevant. ...


It's not simple to either define or to measure what's going on.

--
Best regards,
John Navas
[PLEASE NOTE: Ads belong *only* in rec.photo.marketplace.digital, as per
<http://bobatkins.photo.net/info/charter.htm> <http://rpdfaq.50megs.com/>]
 
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