With regards to closeup/macro magnification, on the 70-300 is the +3(2.9) diopter 6T the only one typically needed, or do people find common use for the +1.5 diopter 5T or for stacking both the 5T and 6T (for +4.4 diopters)? By the formula, the 6T will cover 1/5X to about 9/10X at infinity (no idea what it would be at closest focusing), and the 5T will cover 1/10X to about 1/2X at infinity (and again, what would it be at closest focusing??) The formula I used for infinity is Diopter * FL / 1000 Ross
