Quoted:
Usually focus issues, and that that the camera optics are not the same as an eye.
If the camera was capturing just the reticule (ike you eye does when you are using the device) it would appear larger, but that would defeat the purpose of an advertising picture.
I know, but I'm wondering what exactly the difference is.
Quoted:
If you are talking about the overall size of the reticle, and not the thickness of the circle or the size of the dot, I think it is a "brain effect" not an optical effect. The brain tends to filter out anything we are not concentrating on, so the reticle looks larger because it is what we are paying the most attention to.
I think it is akin to the moon effect where a camera sees the moon as the same size (because it is) whether it is low or high in the sky. Our eyes, interpreted by the brain, see it as larger when very low in the sky. The eyes see the same thing, but the brain presents the same information differently. The camera has no brain to do this.
Just my guess.
It's definitely not a brain effect. You can compare the width of the reticle to the width of the housing. I believe it has something to do with the objective diameter.