Interesting, my daughter is partially sighted and is doing surprisingly well using a nikko sterling 4 -12 zoom with a 50mm objective lens, she also has a tube extender to put her eye up against to block out unwanted light. She needs a lot of light and an easy to find sight beam. bigger magnifications have a narrower sight beam and have less light in the picture. Guess it is a balance. She uses this on a BSA Ultra at .22 for postal competitions. She uses it on full magnification.