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New guy with a dumb question...

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Category: Scopes
Forum Name: Rifle Scopes
Forum Description: Centerfire long gun scopes
URL: http://www.opticstalk.com/forum_posts.asp?TID=20842
Printed Date: March/28/2024 at 10:30
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Topic: New guy with a dumb question...
Posted By: Toad
Subject: New guy with a dumb question...
Date Posted: December/12/2009 at 13:26
After looking at a lot scope specs on the net something is just not connecting in my brain so I thought I would ask the experts...

Why does a 10x scope have a field of view measured at 100yds of around 10-13 feet?

Shouldn't a 10x scope have a field of view that is 10 yards at 100 yards???

100yds/10x = 10yds right?

But according to the specs 100yds/10x = 4yds (or apx 12 feet)

What am I missing here...Loco









Replies:
Posted By: Toad
Date Posted: December/12/2009 at 14:33
So I went to scope school on the FAQ looking for some answers.... I figured out that it has less to do with the magnification and more to do with the focal length of the scope... But I still dont quite get it...


Posted By: silver
Date Posted: December/12/2009 at 14:33
There a lot of stuff you are missing like how things focus on the ocular (back) lens. There a lot of techincal issues that have to deal with where the eye focus for the ocular.  It has to do with eye relief and field of view.  Those two are opposites of the same coin, as one increases, the other decreases.  The magnification affects other factors, but the eye relief and field of view is not dependant on magnification.  Magnification may affect over all factors, that may in effect limit field of view and eye relief.  You are getting the cart before the horse.
 


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Posted By: Ed Connelly
Date Posted: December/12/2009 at 18:45
The higher the magnification ---the smaller the field of view.......imagine a film camera zooming in on a subject.....
 
Back in the Middle Ages people figured a 4X scope gave you anywhere from 22 to 30 feet field of view at 100 yards.  Pretty good for all around use.  Nowadays people think a straight Six Power with 17 feet at 100 yards is okay......some people want EVEN MORE Magnification.....Shocked   6X would be the top for me in a fixed power scope.  If I had a variable I wouldn't be moving it past 6X unless I was shooting TOO FAR AWAY to begin with............


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Posted By: RONK
Date Posted: December/12/2009 at 19:16
Originally posted by Toad Toad wrote:

After looking at a lot scope specs on the net something is just not connecting in my brain so I thought I would ask the experts...

Why does a 10x scope have a field of view measured at 100yds of around 10-13 feet?

Shouldn't a 10x scope have a field of view that is 10 yards at 100 yards???

100yds/10x = 10yds right?

But according to the specs 100yds/10x = 4yds (or apx 12 feet)

What am I missing here...Loco






 Your equation, (In red) is mathematically correct, but absolutely irrelevent to your question.
 There is no optical law that says that the distance to an observed object must be divisible by the magnification, and still equal the F.O.V.
 
No direct correlation whatsoever.
 
 
 


Posted By: Toad
Date Posted: December/12/2009 at 19:25
I used the 10x as an example as I was checking out the Bushnell elite 3200 10x40. I used a friends 10x40 at the range and was impressed with it. I try to keep the KISS (keep it simple stupid) with all my gear. I like the simplicity of a fixed power scope. I've been looking at fixed 6x scopes for my new 7mm/08.

I have it narrowed down to 3

Sightron SII 6x
Weaver K6
Burris Fullfield 6x

Any other suggestions in the $300 or less category?




Posted By: RONK
Date Posted: December/12/2009 at 19:33
The point I was trying to make is that your question was something on the order of asking:
"I drove 100 miles on ten gallons of gas.
100 /10 equals 10, right?
 Then how come it equals 10, and not my tire size, which is 14 inches?"


Posted By: RONK
Date Posted: December/12/2009 at 19:35
 But aside from that, all three 6x scopes you listed should be pretty good ones, for the money if that is what you want on your rifle.


Posted By: Toad
Date Posted: December/12/2009 at 19:47
Originally posted by RONK RONK wrote:

The point I was trying to make is that your question was something on the order of asking:
"I drove 100 miles on ten gallons of gas.
100 /10 equals 10, right?
 Then how come it equals 10, and not my tire size, which is 14 inches?"

I think I get it now. A 10x scope only refers to the magnification not the field of view which is something totally different. I got the two confused thinking the they were correlated. Brain fart I guess... Looking at scope specs on the net for hours at a time can make stuff melt together in nonsensical ways sometimes...


Posted By: RONK
Date Posted: December/12/2009 at 23:55
 Exactly.
 
 All else being equal, more magnification generally means a smaller F.O.V., but there isn't a direct mathematical correlation such as you attempted to make.
 
Incidently, take a look at the IOR 6X at around $350. If you can stretch your budget a little, that one is a very nice 6X , much better by most accounts than the three you mentioned.



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