Scrounging around in the junk bin, I found a screw on Canon video camera 1.4X teleconverter. Not my favourite thing in the world. Hate this kind of poor fix idea actually, but the thread fit my 45mm and the day is wonderful, so a bit of experimenting was to be had.
First up, the close focus was not improved. Shame. Sometimes these things can add a little something to your kit.
Secondly, the thing is sharp.
A couple of things to note about quick fix close focus options.
Extension Tubes are optically pure (no glass), but are fiddly, loose light (1/2-2 stops depending on length) and are more powerful on short lenses.
Screw in diopters are (usually) less well optically corrected, don't loose much or any light and are better on longer lenses.
Tele converters are a good option if they are good to start with. The lens gains 1.4 to 2x magnification, but the minimum focus range stays the same.
The crop and the full size image. It turned out to be a great working distance for insects, but not close enough for serious work.
Next up, the Olympus 25mm....from a million years ago. Kirk tuck is a big fan of Olympus Pen lenses from the original half frame era, but the 25mm I saved from the tip during a work clean out is not one of the best of the bunch.
The first image is the slightly hazy, low contrast original. The second is the same image with a preset applied (called 70's designed to look like the 1970-80's film era) and the last is from the new 25mm f1.8, all shot at f4. The difference in the bokeh is noticeable.