Extension ring recommendations

[Stanga]

I tried extension tubes but I am getting CA issues with them.

 

[Petrochemist]

I know. The difficulty is there aren't any 300mm macros, so this particular niche of photography's more about finding or creating close focusing long glass. For m43 one could make a case for adapting Canon, Nikon, or Sigma's 180 or 200mm macros but those are fairly expensive (and heavy) lenses. The Olympus 300 isn't much of an improvement over the 100-300 II (0.24x versus 0.21x) and the Panasonic-Leica 200 and Olympus 75-300 II are worse (~0.2x and 0.18x). The Panasonic-Leica 100-400 isn't much different either (0.25x), though there are 400s in other systems which focus a bit closer and provide just that extra bit of magnification that's needed here. Several of these are more expensive and heavier than the full frame macros so the 100-300 II's arguably the most attractive native option to start with.

Which makes this sort of an interesting exercise. After some more poking around the Minolta No. 0 appears to be a +0.94 achromat but it seems 55mm is the largest size. Results from the better single element +1 diopters are fairly good so those might be worth a try. Most are on the expensive side but the single coated B+W NL1 SC could be worth a look as a lower cost option.

There's no need to limit yourself to native lenses - there is the Tamron 54B 300mm 'telemacro' - It doesn't reach 1:1 being limited to 0.3x unless you add a teleconverter - but it manages OK for butterfly/dragonfly style shots if you can manually focus.

Adding a +1 diopter to the lens (without the teleconverter) gives a lens that will still focus to 1m, yet gives 0.69x magnification at closest focus (which has dropped from 14cm to 12.3cm due to the diopter)

I do wish there were some affordable weak diopters in large sizes. I've looked for a +0.3 to go on my 'Bigmos' to reduce the minimum focus distance from 2.2m. This should give a focusing range of ~1.35 to 3.3m ideal for newts etc. I couldn't find anything less than +1 - giving a focusing range 0.7 to 1m rather limited, but nowhere near as bad as the +8 I first brought (full focusing range 118cm to 125cm) which leaves the focusing control pretty much useless.

The reality is of course the Bigmos is just not suited to close-ups, and lighter/cheaper lenses can do the job much better.