How Do I Measure Noise Using Photoshop? And What Is A Significant Change?

Started 2 months ago | Discussions thread
ken_in_nh Regular Member • Posts: 259
Re: How Do I Measure Noise Using Photoshop? And What Is A Significant Change?

MrBrightSide wrote:

Question 1: Long ago I remember reading that you could use the statistics tools in Photoshop to measure the noise in a photograph. There must be something in the program because it has noise reduction so it must be able to identify noise. How does it work?

I think you may be thinking of the long gone scientific version of Photoshop, which had a generous set of measurement tools built in, but none for formal noise measurement IIRC.

Failing that, what other simple methods are there to measure noise in digital photos.

No simple way to measure noise. In electronic circuits, noise is typically measured (if it's measured at all these days) using standardized signals - usually from a tone generator which generates a pure sine or pure square wave, although with the latter, you don't measure true noise, but ringing and such instead.

In photography, you'd measure noise with a very uniform grey scale, and measure it at different light intensities. But why?

Question 2: Once the noise is measure what constitutes a significant difference in the noise level? Does it fall at 1 percent noisier? 10 percent? 100 percent?

You're thinking about it the wrong way. Outside scientific imaging, and go to Edmund's Optics (https://www.edmundoptics.com/ ) if you want to learn more about that, photography is largely perceptual, artistic if you will.  This means that one's reaction to noise in an image is both highly subjective, and variable depending on the scene and artistic intent.  That's why grain, a kind of noise, is a plus in some images.

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