Family guy you're right on. What scope are you using? I couldn't agree more on the reticle and have toyed around with getting one.
From Optics Planet (laymans explanation):
Scopes don't gather light, as most people think, although the term "light gathering ability" has become accepted jargon. Scopes transmit available light through the lenses to your eye, always losing a bit in the process. The best a scope can hope to offer in light transmission is about a theoretical 98%, which only the very finest (read expensive) scopes can hope to approach. Anything above 95% is considered great, and most scopes are around 90%, give or take a bit.
The more magnification you have, the less light you get to your eyepiece. The larger the objective lens, the more you get through your eyepiece.
Aged eyes may dilate to only about four millimeters. Younger eyes may open up to seven millimeters and even more.
The small circle of light that appears in the eyepiece when you hold a scope at arms length is called an exit pupil. Here's an interesting experiment to help explain it. Take a variable scope, put it at its lowest power, and hold it at arms length. See the circle of light in the ocular lens? That is the exit pupil. The diameter of it in millimeters is the exit pupil size. Now turn the scope up to its highest power and try it again. See how much smaller it gets? Imagine if you are using this scope during poor lighting conditions as common in hunting situations, like dawn or dusk. How small and dark will that exit pupil be? How well do you think you'll be able to see through that tiny circle of light?
A formula for exit pupil is as follows: Divide the objective lens size in millimeters by the magnification. Example: if your 3-9X40 scope is set at 3X, 40 divided by 3 equals 13.3 millimeters, which is large enough for almost all low light applications. If your scope is set at 9X, 40 divided by 9 equals 4.44millimeters. The difference in available light from the larger exit pupil is significant.
Also remember that, if the exit pupil is larger than your actual pupil, then you're wasting light. Exit pupil is calculated by dividing the objective lens size by the viewing lens size.
So for example, let's say you have two scopes that are 3-9 power, one with 50mm and one with 40mm objective, and they are both dialed to 3 power. The 50mm scope has an exit pupil of 16.67 (i.e. 50/3), and the 40mm scope has an exit pupil of 13.33 (i.e. 40/3). In this scenario, most of the light is not going in your pupil. So assuming they both have the same light transmission percentage, the image will look the same brightness in both scopes, and the 50mm was overkill.
But now take this scenario. It's getting late, and you need to dial the scope up in magnification to see your target. Same two scopes, exact same light transmission percentage. And let's assume your actual pupil goes to 6mm when dark adjusted. With the 50mm scope, you can dial the magnification up as high as 8.33 and the picture will not get any darker. (After that, the exit pupil starts getting smaller than your actual pupil, and the image appears darker.) With the 40mm scope, you can dial up to 6.67 power without the picture getting any darker. Not really a big difference there -- unless you really need another 1.7x magnification in the last few minutes of shooting light.
Here's info on a couple scopes that I own, that may help you out. I have a Bushnell 3-9x40 in the Elite 3200 and another in Elite 4200 series. The 3200 is 91% and the 4200 is advertised 95% light transmission. In low light, I can dial either one of them up to about 5.75 power before I can see the image start to get darker. However, I've taken both into the stand several times, and looked through them in the last minute or two of shooting light. The 4200 gave me maybe 4-5 more minutes where I could see enough to watch the deer and take a shot if I wanted to. That's on a deer plot with about 150 yard maximum range shot.
I would rarely take a shot over 150 yards where I hunt, especially if it was the final few minutes of light. So in my case, the light transmission number trumps the 50mm objective every time. I would rather have a few more minutes of shooting time than I would that extra magnification I would get from a larger objective. You have to look at your likely hunting scenarios and decide for yourself though.
