1 minute of work with the color range selection and converting to a layer mask:
1) Select->Color Range, and set the selection preview to "White Matte"
2) click on the background (choose an average background colour, not the dark patches). Invert the selection (click on the checkbox)
3) switch to "Highlights". The dark patches disappear.
4) click on OK
5) apply the selection as a layer mask. (you may have to convert the background layer to a normal layer by <ALT> double-clicking it first)
6) optional: convert the layer to a smart object, and add black and white adjustment layer. Then use a black brush to restore the coloured areas (circles).
Great! and thanks...for revealing this routine. Awesome
No problem - I had to do this type of work in the past as well. You can add a curves adjustment layer to increase the contrast in specific areas as well.