My lenses are: Sigma 18-250mm: soft pictures, min focusing distance around 15cm (yes 15!!!) at 250mm
Canon 50mm 1.8, min focusing distance 45cm
1) will the macro make the sigma so close you can't get a proper picture/distortion etc?
2) no point doing it to the canon? will it get anywhere near the sigma in terms of max macro since the sigma is 5x the magnification already and 3x the "near-ness" even with no tube
3) I can't control aperture: can you set to aperture priority, set aperture, dismount lens, attach extension tube and "set" you aperture this way?
4) any other thoughts ...