Scope ratings
01-18-2004, 04:33 PM
#1
Fork Horn
Thread Starter
Join Date: Jan 2004
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Posts: 482
Scope ratings
I see the different ratings of scopes (2-7x33mm, 3-9x40mm, 4-12x40mm, etc...)and was wanting to know what it means? If I do most of my shooting at 100 yds. or less what would be the best scope? How about up to 300 yds? I want to learn how to select a scope to fit my shooting. Thanks.
01-18-2004, 05:49 PM
#2
Boone & Crockett
Join Date: Feb 2003
Posts: 10,679
RE: Scope ratings
The first two numbers represent the scopes magnification. The last number represents the scopes objective lense (farthest lense from the eye) size in milimeters.
A 3-9X40 would make an object to appear 3 times to 9 times larger than actual size. The larger the objective lense is the more light it will permit to enter your eye all other things being equal.
Many folks will place a scope of 1.5-5X or a 2-7X if they are expecting only short range shots. On the oposite end folks might jump up to a 4-12X or a 4-16X if they are hunting in very open terrain, such as would be the case for western pronghorn and plains mule deer. A 3-9X scope is a good all around magnification to use where you plan on having close in as well as farther shots.
A 3-9X40 would make an object to appear 3 times to 9 times larger than actual size. The larger the objective lense is the more light it will permit to enter your eye all other things being equal.
Many folks will place a scope of 1.5-5X or a 2-7X if they are expecting only short range shots. On the oposite end folks might jump up to a 4-12X or a 4-16X if they are hunting in very open terrain, such as would be the case for western pronghorn and plains mule deer. A 3-9X scope is a good all around magnification to use where you plan on having close in as well as farther shots.
01-18-2004, 06:28 PM
#3
Giant Nontypical
Join Date: Feb 2003
Location: fort mcmurray alberta canada
Posts: 5,667
RE: Scope ratings
Be sure to check the manufacturers websites as some scopes labels do not actually represent their true magnifications.For example the 3.5x10 leupolds are actually 3.3 x9.7 power.
01-19-2004, 06:21 AM
#4
Giant Nontypical
Join Date: Feb 2003
Location: Texas - BUT NOW in Madison County, NY
Posts: 6,270
RE: Scope ratings
If I do most of my shooting at 100 yds. or less what would be the best scope? How about up to 300 yds? I want to learn how to select a scope to fit my shooting. Thanks.
01-21-2004, 09:58 AM
#6
Giant Nontypical
Join Date: Feb 2003
Location: Texas - BUT NOW in Madison County, NY
Posts: 6,270
RE: Scope ratings
3-9X40 would make an object to appear 3 times to 9 times larger than actual size. The larger the objective lense is the more light it will permit to enter your eye all other things being equal.
EXAMPLE: An 8X56mm scope will give you 7mm of exit pupil, ALL of which your eye can use if completely dilated. A 4X with a 40mm objective gives you a 10mm exit pupil, of which your eye can only use 7mm (MAX) when completely dilated.
01-21-2004, 05:36 PM
#7
Fork Horn
Thread Starter
Join Date: Jan 2004
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Posts: 482
RE: Scope ratings
ORIGINAL: eldeguello
The clear diameter of the objective lens, divided by the magnification = the exit pupil diameter (size of light beam coming out of the ocular lens). Your eye can only open up enough to use a 7mm exit pupil - anything larger than 7mm is wasted!
EXAMPLE: An 8X56mm scope will give you 7mm of exit pupil, ALL of which your eye can use if completely dilated. A 4X with a 40mm objective gives you a 10mm exit pupil, of which your eye can only use 7mm (MAX) when completely dilated.
3-9X40 would make an object to appear 3 times to 9 times larger than actual size. The larger the objective lense is the more light it will permit to enter your eye all other things being equal.
EXAMPLE: An 8X56mm scope will give you 7mm of exit pupil, ALL of which your eye can use if completely dilated. A 4X with a 40mm objective gives you a 10mm exit pupil, of which your eye can only use 7mm (MAX) when completely dilated.
01-21-2004, 06:16 PM
#8
Boone & Crockett
Join Date: Feb 2003
Posts: 10,679
RE: Scope ratings
Interesting. So a 3-9x40mm scope will give you an exit pupil diameter of 4mm. Which the eye, when fully dilated, will see everything in the lense. (Nothing wasted) Is that correct?
With an exit pupil size the same size as your eyes pupil you will get the maximum ammount of light. If the light is smaller than your eyes pupil then as the ambient light gets dim the less light your eye will have to use and your sighe picture will be dim. If the light is larger than your pupil size then some of the available light is not being used.
01-21-2004, 07:41 PM
#10
Giant Nontypical
Join Date: Feb 2003
Location: fort mcmurray alberta canada
Posts: 5,667
RE: Scope ratings
Lens coatings also have a big effect on the brightness of a scope.A 40mm scope with top quality coatings can be brighter than a 50mm scope with poor quality coatings at the same power setting.
