I do have a set of extension tubes that I use when needed, rarely. I compared the sony 100 macro to the ZA 135 + extension at 1:1. Sharpness was quite similar, higher contrast and CA on the ZA. Optically a good combination but the 1 kg lens is too heavy on tha rather flimsy tube so I prefer to use the sony. I also used the ZS 50 a few times with a small extension to improve the MFD stopped down at f/16. The results were average as you would expect from a non macro lens used at this close distance and aperture but very usable.
