I have created a couple of quartz filters to reduce the size of PDFs. For this I use Image Compression - which is pretty straight forward (just use JPEG and the a suitable quality level) - but there is also a filter called Image Sampling that also offers a quality level (low, medium, high).
I have tried it but I don't notice any significant difference. On what quality of the PDF is this option supposed to apply?
The other alternatives (size, resolution, scaling) in the Image Sampling filter are straightforward but I don't understand why there is a quality option in both Image Sampling and Image Compression.