Feel bored this afternoon, and explore all the combination with possibility and Result demo in photo for the Magnification rate.
actual stuff used in this test,
1. cheapest Pentax AF lens: DAL18-55mm f3.5-5.6
2. cheapest Pentax 135mm lens: M 135mm f3.5
3. any 50mm will do, I use M 50mm f1.4
4. cheap Extension tube 10mm, 20mm, 30mm
5. cheap PK-52mm reverse mount
6. cheap 52-49mm male-to-male thread ring, (optional 49-52 step-up ring)
Test 1: "Extension Tube is your best friend for cheap macro, make every lens a macro lens"
50mm f1.4 with 60mm Extension tube on Pentax DSLR K-x; (ant is 3mm)
actual rule image for you calculation, around 1:1 range, Object Distance around 10cm, good enough distant
135mm f3.5 with 60mm Extension tube on Pentax DSLR K-x; Object Distance around 80cm, quite a distance
Vivitar 19-35mm at 28mm with 35mm extension tube, object distance around 5mm, too close, almost touch the glass, beyong 28mm, touch glass already, cant focus
Vivitar 19-35mm at 35mm with 35mm extension tube, object distance around 5mm, too close,almost touch glass
Conclusion:
- extension tube reduce minimum focus distance to gain magnification, so short lens are likely easy to cut off the whole distance, make it too close to object.