I always have a hard time wrapping my head around optics, and this is something that has been puzzling me.

Can anyone explain why, on pictures like this one:

the reticle looks so small?
An illustration would also be great, they usually make this sort of thing a lot easier to understand.

Since I can't see the picture, I really can't even take a guess, but are you talking about just a dot, a dot and ring, or what. By "smaller" do you mean that the dot is larger and the lines are thicker?

Try the photo again, or please clarify.

Looks like the site has anti-embedding functionality.

Here is the page containing the picture:http://www.thetruthaboutguns.com/2011/02/chris-dumm/gear-review-eotech-vs-aimpoint-vs-primary-arms-red-dot-scopes/eotech-reticle/

Same thing here:
http://www.thetruthaboutguns.com/2011/02/chris-dumm/gear-review-eotech-vs-aimpoint-vs-primary-arms-red-dot-scopes/eotech-max-brightness/
The reticle would be much larger to an eye.

I think I can embed this one:

The reticle never looks that small to an eye.
The same thing happens with my cell phone camera.

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.

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.

I know, but I'm wondering what exactly the difference is.






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.

Try comparing it to the ears on the front sight.

The reticule is placed at 'infinite' focus so it appears sharp when viewed against the background.
The camera cannot record images like this unless you can get the lens almost in contact wit the objective surface ad also set the focus to infinity.

Th same problem occurs when you try to take a picture through a microscope, telescope, or binoculars.
The camera lens is not at the correct distance from the objective.

Placing the camera lens front surface at the correct distance for an eye still results in changes in the image field usually.
The lens is markedly larger than the human eye in most cases, though some of the smaller camera lenses on electronic camera are getting pretty close. to eye aperture size.