I was thinking about using the 135 with extension tubes for macro work. I have a 180 macro. How would the 135 compare with the 100 for macro work and how would the 100 macro compare with teh 135 for distance?
The 135mm is a very sharp lens but macro lenses are designed for flat field and minimised aberations at high magnifications.
May not be too much of a problem as long as you are not doing copying work where flatness of field is important.