Need to shrink the size of all images files in a folder
I have a folder with high res. pictures from my Canon and iPhone. They are fine to keep, since I need the detail as my research continues long after I take the pictures. But as email attachments, they are too large.
I need to shrink them both in their physical size an the resolution.
By "physical size' I mean when I open them in Finder, the Preview size can be reduced.
How can i best do this mass reduction on a Mac?