Optics question..... why?

F

fullmoon01

New member
I have posted this question elsewhere but will try here also to see if anybody has a clue what I am talking about.. /ubbthreads/images/graemlins/confused1.gif
It has come to my attention that some scopes have the feel of looking through a long tube while others a short tube. Why is this? Let me explain. It seems like my 4x scopes have a nice big magnified image directly in front of my eye with only a thin dark circle surrounding the image from the light of the outside world but most (not all) of my variable scopes have a magnified image that looks like it is at the end of a pipe which creates a thick black ring surrounding the image and thus their 4x magnification looks much less than the fixed 4x image. What creates this and what is it called? There has to be a term for it in the scope making industry. What ever it is called I don't like it. I have an el-cheapo Simmons 8-point scope that I have always liked and it just dawned on me recently WHY I liked it. It has a big fat image like my fixed power 4x's and it is a 3-9x40!
Others have suggested I have the wrong eye relief but that does not appear to be the issue. I can move my head nearer or farther from the scope and it only gets worse. The ring is "built into" the scopes design and cannot be adjusted out it seems. Maybe it has something to do with the exit pupil size??
 
If the dark ring is visible to you on all your scopes even when you move your head nearer or farther from the scope you may have a vision problem. There should be no dark ring at all if you have the proper eye relief. Have someone else look through your scope and find out if they see the same thing. You might also try looking through their scopes. All scopes have some darkening at the edges but that shouldn't appear as a pronounced ring.

If your buddy doesn't see the dark ring, I would suggest you have an eye exam... I'm being serious here.

Could the dark ring you are seeing actually be edge diffusion? That is when the edge of the image isn't as sharp or as high in contrast as the center of the image. This could very well be what you are seeing. It usually is more pronounced in cheaper or older non-coated scopes.

It's like when you focus light from a magnifing glass on an object the center is brighter than the outer edge.

Hope that helps!

Nikonut
 
It would be so much easier if I could just show you. I really need to draw a picture and somehow get it on the web. My friends and kids have noticed it too but not until I pointed it out. ARRGGGG! It's like trying to explain colors to a blind man at this point. You just have to see the difference to realize it. Thanks for the help though.
 
Back
Top