I have a good understanding of unsharp mask going back to my Uncle explaining to me in the 1960s how he did it using enlargers. I have knowledge of some other algorithms as a result of reading IEEE Computer Graphics and ACM Siggraph journals some decades ago, but have not kept up with what has been done recently.
Does the "sharpness" setting in DPP use an unsharp mask but set the parameters automatically or does it use another algorithm. If it uses a convolution kernel, then why would not both sharpness and unsharp mask be available for the same image.
https://cam.start.canon/en/S002/manual/html/UG-04_EditImage_0040.html#EditImage_0050_15
https://en.wikipedia.org/wiki/Unsharp_masking
A "sharpen" convolution kernel might be adjusted by only changing a single parameter the magnitude of the central point, but the size of the kernel might also be adjusted. The sharpen kernel mentioned by https://en.wikipedia.org/wiki/Kernel_(image_processing) will increase contrast at edges, but could be done together with unsharp mask.
It has seemed to me from comments in other forums that many camera users have little knowledge of image sharpening algorithms. I have only noticed the unsharp mask algorithm mentioned by name in DPP, but one might guess that diffraction blur correction uses Richardson/Lucy deconvolution or something similar and sets the parameters automatically. Diffraction correction is also included in digital lens optimizer as evidence for my guess.
Mentioning the algorithms by name in the DPP manual would enable users to look them up and make better decisions about parameters and amounts. It might also dispel some wrong information about what DPP does.
