Standard deviation for noise

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Juza
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Standard deviation for noise

Unread postby Juza » 06.08.2004 20:32

Hi,
I downloaded the new Noise filter Home, it looks greatly improved from the previous - already nice - versions :-)

Just one question : is it possible to measure the standard deviation for noise? IMO it could be an useful feature (al least for those like me that love to spend time doing in-depth tests of the cameras).
Juza | www.juzaphoto.com

May beauty be everywhere around me

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Dan Kozub
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Joined: 24.03.2004 18:14

Unread postby Dan Kozub » 07.08.2004 10:31

Now noise level is calculated as an average absolute deviation from the average signal level in some area. Size of the area - 10 by 10 pixels.

Switch from percents to absolute values (button after midtones slider).
Than click on image with right button - you will see green square (area to measure noise) and detected level on appropriate slider.

I think this parameter is good enough to compare noise level in different images. Let me know about results of your research, Juze.

Danilo

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Juza
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Unread postby Juza » 08.08.2004 21:52

Hi Dan,
thank you for the answer.

I tried the absolute value...It could be perfect to as parameter of comparison, but I think that the 10x10 are is too small to get a precise value ( anyway, the software works well so I think that for the 99% of the users it wouldn't be a problem ;-) ).

I tried to measure the noise of my camera (Nikon D70); the following example refers to iso 1600 (the test target can be downloaded here : http://www.juzaphoto.com/npn/1600.zip ).
I toke an OOF image of an uniform gray card and then I toke a 256x256 pixel crop from the center of the photo. I measured the absolute value on the top left corner and the value was 52 ( screenshot : http://www.juzaphoto.com/npn/helicon_home_1.jpg ). Then, I measured the value on another area and it was 65 ( screenshot : http://www.juzaphoto.com/npn/helicon_home_2.jpg ) . Other measurements were 55,46,61,57, etc.

It could be an interesting possibility to give to the users the option to choose the measurement area...for example, one could use the default size 10x10 if he want a fast measurement, or instead a bigger size (for example 250x250 px) if he needs an extremely accurate value.


Juza
Juza | www.juzaphoto.com



May beauty be everywhere around me

Guest

Unread postby Guest » 08.08.2004 22:40

Juza,

Ok, we will implement this "secret" feature especially for you in the next version :)
I plan to release new version this week, so wait a couple of days.

I've seen your photos (juzaphoto.com) - they are just beautiful! I love wild nature and mountains.

Regards,

Dan

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Juza
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Joined: 24.04.2004 17:37
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Unread postby Juza » 12.08.2004 01:18

Thanks! :D :D :D
Juza | www.juzaphoto.com



May beauty be everywhere around me


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