i never experimented with close-up filters before. but because of the minimum focus distance on my Mamiya 150mm f/2.8 being 1.5 meters, i started looking into it. i was wondering if it changed the field of view and that's why it allowed "close-up." anyway, luckily, when I ordered a close-up filter set in 67mm, it would fit my Mamiya 80 and 150 lenses, as well as my Bronica 80 and 150 lenses.
here's a 6x6cm frame with an 80mm f/2.8 and a +2 diopter filter. they do not change the field of view of the lens, they just convert the focusing range from (example) 0.8m - infinity to something like .2m - .5m.
you definitely lose the ability to focus to infinity, or more specifically, on anything past that converted far-focus distance, in this case .5m or so. fun possibilities with portraits.
the depth of field here is probably about 10mm. shot at f/2.8.