How Magnification Influences Target Size And Clarity

by
posted on August 26, 2019
1-imageclarity.jpg

A reader submitted this question about target size at long distances when viewed through a scope with a higher magnification level, and at shorter distances with lower magnification.

Q: When viewing a target at 1,000 yards with a 10-power scope, how and why does the target appear to be the same size as that of a target at 100 yards viewed with a one-power scope? 

A: The basic idea is that the two factors of 10 (the distance between the scope and the target, and 10 times the magnification) will cancel each other out, even though the 1,000-yard target is 10 times the distance from the scope. 

This occurs because the human eye interprets the size of a distant object based on the angle it subtends, or seems to occupy in space. For target-size objects at typical shooting distances, the subtension of the target decreases in direct proportion to the distance. So, when viewed with your naked eye at one times the magnification, a target at 1,000 yards has ⅒ the size of the same target at 100 yards.

A scope’s job is to create an image of the target that has a subtension greater than that seen by the naked eye. This is made possible by using a number of lenses with precisely defined focal lengths and spacings. A 10-power scope will magnify the subtension, or apparent size of anything you look at by a factor of 10. So, even though the 1,000-yard target is 10 times as far away, a 10-power scope will boost its subtension exactly enough to make it seem to be the same size as a 100-yard target viewed with a one-power scope.

Subtension and magnification in long range optics
Environmental factors also influence optical image clarity at long distances.


Even though the 1,000-yard target may appear the same size as the 100-yard target with a 10-power scope, it may not appear as clear. This is due to either the construction or quality of the scope, or environmental factors that can influence the image perception. If the construction or quality of the scope is poor, the picture will not be as clear as that seen with a well-made scope. If you throw environmental factors into the picture, the image will be even poorer. With a 1,000-yard target viewed with a 10-power scope, you have 1,000 yards of humidity, heat mirage, airborne particles, etc. that will be magnified by the scope as well. In magnifying all of these environmental factors, the clarity of the target is sacrificed.

A large оbјесtіvе lеnѕ can provide а brіghtеr іmаgе, however both clаrіtу аnd brіghtnеѕѕ are influenced by glаѕѕ quаlіtу. Іf уоu don’t want to suffer from a subpar vіѕuаl ехреrіеnсе when using уоur ѕсоре, lооk fоr quаlіtу optics thаt include anti-glare and anti-reflection coatings that іmрrоvе lіght trаnѕmіѕѕіоn.


Do you have a question about competitive shooting or equipment? Send your questions to us at [email protected]We look forward to hearing from you.

Latest

Weisz Maddalena 1
Weisz Maddalena 1

USA Shooting: Weisz, Maddalena Both Earn Bronze At 2022 ISSF President’s Cup

Alison Weisz and Sagen Maddalena captured Women’s 10m Air Rifle bronze medals on December 2 at the 2022 ISSF President’s Cup in Cairo, Egypt

Henry Repeating Arms Makes $50,000 Donation To First Responders Children’s Foundation

The First Responders Children’s Foundation supports the children and families of first responders who have been killed or injured in the line of duty

USPSA Area 5 Championship: Every Challenging Target You Can Think Of In One Match

Results of the 2022 USPSA Area 5 Championship held this past July in Brooklyn, Michigan

2022 IPSC World Shoot: Luke Cao Wins Production Optics Light Division

Team Walther’s Luke Cao captures Production Optics Light title at 2022 IPSC World Shoot in Pattaya, Thailand

SIG Sauer Romeo2: A Modular Red Dot

SIG Sauer’s Romeo2 modular red-dot reflex sight gives users the choice of open- or closed-emitter styles

ISSF President’s Cup: Ali Weisz, Sagen Maddalena Capture Bronze Medals In Cairo For USA Shooting

USA Shooting’s Ali Weisz, Sagen Maddalena land bronze medals in 10m Women’s Air Rifle event at 2022 ISSF President’s Cup in Egypt

Interests



Get the best of Shooting Sports USA delivered to your inbox.