Hi Robert

for me and any others who are more interested in the answer to a problem than capable of following the maths in the middle, are you able to improve on my empirical blundering (obviously taking an image where there is some detail worth keeping) -

Taking an image that has to be scaled down to about 33% for forum display, I find Lanczos 3 compression has a marginal edge on the image reduced to 768H over Bicubic or Mitchell. Comparing original at 67% & reductions at 200%, Lanczos still has an edge. Comparing the original at its full size and the reductions at 300%, there is virtually nothing to choose between the compressed images.

But there is still a little to be gained on going back over the Lanczos reduced image using 'Local contrast enhancement'. LCE, being done with controlled values, seems much more successful than 'bicubic with sharpen'.

I suspect that there is then no universal answer to the last bit, ie whether in general it is best to use the more subtle sharpening techniques before or after compression? (getting a better camera, better lens and always using a tripod not being a realistic option)