Allow me if you will to throw in a little about the things I know about scopes.
1. Light does indeed travel in straight lines, however incidental light hitting a lens can cause images to be affected because of internal reflections with in the lenses. I usually therefore add a 4" or longer mirage tube to the scope as shown below.
However, I believe the most pronounced effect on POI is caused by incorrectly set parallax adjustments. 2 to 4 moa variations can result if parallax is set improperly.
2. Increased magnification does result in a reduction of lens transmission efficiency. It has been my practical experience that increasing the objective size can compensate for this to some extent. Most noticeable is the effect of a 58mm objective on my 6-30x58 SN3. This scope by the way has a 35mm tube which increases allowable erector tube travel. However, for lower powers (and the function appears to be non-linear) say 12x to 15x and below don't require larger objectives unless shooting in lowlight conditions, again in my opinion.
3. Coatings tend to enhance color fidelity and may therefore increase resolution indirectly, by making color boundaries on the target more apparent.
4. Lens centration, the alignment of their axis is important in maximizing lens performance. This is a direct result of accuracy of tube construction and lens mounting system.
5. I find that with premium scopes that mirage becomes (and this is a subjective judgment) incremental rather than continuous, allowing it to be seen and therefore shot through. The mirage distortion appears to be in waves rather than a continuous blur.
[ 06-14-2004: Message edited by: DMCI ]