I purchased a Swarovski z5 5-25X52, Leupold VX-6 4-24X52 and Bushnell 6500 4 1/2-30X50. I also had a Leupold 4 1/2-14X50. All three of the first three were noticeably better than the latter. So if you want the best for light, get one of them. So far none of the other scopes in the same magnification range that I have purchased stay with these for low light. That includes Nikon Monarch 3 5-20X44, Zeiss HD5 Conquest 5-25X50, Minox ZX5 5-25x56 SF. The scopes that regularly beat these in low light are the Nightforce with 56mm objective.
