chuffalump
Well-known member
I was looking for a low cost scope and found a couple in the ?25 range. Thing is, they were classified by magnification rather than dioptre.
So I looked it up. Ignoring the magnification vs lens power fudge. A lens dioptre is it's magnification x 4. I've seen people recommend dioptres from 0.5 to 0.75. These are tiny magnifications. How can cheaper scopes be classed as four or eight X magnification (16 to 32 dioptre)?
A .75 D lens focuses light at 1.3m, .5 D is 2m so it makes sense that I've seen recommendations of smaller dioptres for longer DL.
Hmmph. It occurs to me that the 4X or 8X could refer to the apparent magnification at a standardised DL rather than the actual optical physics definition.
So I looked it up. Ignoring the magnification vs lens power fudge. A lens dioptre is it's magnification x 4. I've seen people recommend dioptres from 0.5 to 0.75. These are tiny magnifications. How can cheaper scopes be classed as four or eight X magnification (16 to 32 dioptre)?
A .75 D lens focuses light at 1.3m, .5 D is 2m so it makes sense that I've seen recommendations of smaller dioptres for longer DL.
Hmmph. It occurs to me that the 4X or 8X could refer to the apparent magnification at a standardised DL rather than the actual optical physics definition.