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

Started 2 months ago | Discussions thread
FingerPainter Veteran Member • Posts: 8,334
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

I'm not so sure about that. I am unaware of Photoshop having a facility to calculate and report the SNR of a photo, but my familiarity with PS is limited, so don't take that as a definite assertion that PS cannot do it.

to measure the noise in a photograph.

The usual measurement for noise in a photo is Signal to Noise Ratio (SNR), expressed in decibels (dB). The SNR of images taken with modern digital cameras tends to track the square root of the exposure (in lux seconds) closely.

There must be something in the program because it has noise reduction so it must be able to identify noise. How does it work?

PS can recognize noise and treat it because noise is variation in pixel values. It can treat the problem locally without calculating the magnitude of the problem over the whole image.

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

If it was both simple and useful, I'd expect it to be a common tool in photographic development software.

A program more likely to be able to calculate and report SNR would be RawDigger.

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?

A 3dB difference, which represents the change in noisiness related to a change of 1 stop of exposure, can often be detected by the human eye, but perhaps not without pixel peeping.

Question 3: There is no question 3. This is a reminder that no one has the patience for your thoughts about subjectivity and how everyone has a different pain threshold when it comes to noise.

I'm not sure it is wise to assume everybody has your level of tolerance.

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