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

Started 2 months ago | Discussions thread
Mark Scott Abeln
Mark Scott Abeln Forum Pro • Posts: 14,376
Measurement is futile

MrBrightSide wrote:

That’s deep. Are you saying that trying to measure noise is futile?

What is futile is trying to measure noise in a JPEG or TIFF, where at a minimum, the noise characteristics would change with color, camera profile, white balance, etc. It would be difficult to get good results unless you are quite systematic: also, the results may be misleading.

Shooting a ColorChecker target under varying but consistent conditions could be useful, but only as long as you are systematic.

A synthetic approach, where you start with basic raw noise measurements and then estimate the final image noise characteristics—after raw conversion—can be quite informative. The measurement phase is rather easier, as you only measure grayscale values, but you need to figure out what calculations are needed to get a full color image (there is some published data): and from this, it’s fairly easy to get color noise estimates, which can be compared against actual images. Any great discrepancies can then be analyzed.

Published noise figures for sensors typically only consider these raw measurements, and then only for the green channel. Discussions about noise with colors is usually highly anecdotal and surprisingly little hard data is commonly available; unfortunately it varies with processing and shooting conditions, ensuring unresolved arguments for years to come.

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