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Posted: 10/13/2002 12:28:18 PM EDT
| A 2.5 x 28 will have wider field of view, but a 4 x 40 of comparable quality will gather more light - brighter in low light. correct? |
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Yes and nope. All things being equal a 2.5x scope is going to have a much wider field of view than a 4x scope. All things being equal your 2.5 x 28 mm will have a tiny bit more light gathering than the 4 x 40 mm. The math is the power of the scope divided by the size of the front objective in millimeters. The human pupil expands to about 8 mm in darkness - so anything above 8 is not used by the eye but mearly lights up the outside of the eye. About 8 mm ... I've heard 10 mm tossed around too. Your first scope has a 11.2 mm light cone output, the second a 10 mm cone which would mean that the 2.5 scope would have a bit more light all things being equal ... which they rarely are. A good quality scope will have better surfaces than a cheap one and even though they would seem equal on paper the truth is the better scope would be brighter. |
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