Frequency?

[phil146]

I would appreciate a definition frequency as it applies to Affinity Photo.  I understand the idea of frequency as in the EM spectrum but not sure what it means when applied to tones in an image.  Thanks

[DM1]

High Frequency layer shows 'Textures', Low Frequency layer shows 'Colour and Tones'. 

Explained here.

 

[IanSG]

There's a fairly detailed discussion here.

[John Rostron]

Strictly, frequency refers to only a part of an image. If you look at the girl's hair above, this is a high-frequency part of the image. The pixel values change rapidly with position. If you look at her cheek, the pixel values do not change much with position. This is a low-frequency part of the image. People use 'a high-frequency image' to refer to an image in which high frequency areas dominate. In a low frequency image, the low frequency areas dominate.

John

[phil146]

Thanks to all 3 of you for your responses-both in how to use the high/low frequencies for image processing and the theory behind it. DM1-Excellent tutorial on how to apply the concept; to Ian and John-the links to signal processing and Fourier are what I want to understand.  That gives me plenty to study about spatial frequency-it's been a long time since I encountered Fourier analysis in college.