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Rifle Scope Light Transmission Comparison: Why It’s Needed

Rifle Scope Light Transmission Comparison

How do you ensure the scope’s quality low light performance?

Are there any other factors about light transmission that you should know about? More importantly, are there any misconceptions that you are better off knowing?

If you’re STILL asking any one of these questions, then it may be high time that you read through this article.

We’re here to break down light transmission to what it really just is: BRIGHTNESS.

Let’s Talk About Brightness

Brightness

Does the concept of low-light performance still sound too technical for you? It would help to remember that it simply refers to how well and bright you can see in a low-light environment.

There are FIVE ESSENTIALS for a riflescope to perform well under such conditions:

  • Large exit pupil to maximize your eye’s light processing ability
  • Large front objective compared to other parts to absorb more light
  • Ample size of the main tube to facilitate passage of light
  • Good light transmission to ensure better imaging
  • Allowance of lens coating to minimize reflection

It’s sacred for hunters and tactical shooters to equip their rifles with scopes of low-light performance. How else would you expect a hunt to go at dusk or dawn without this feature?

Great! Now that’s out of the way… why is this important again?

Comparing Light Transmission Among Rifle Scopes

Comparing

Believe it or not, light transmission is more complex than the five essentials for scopes. There’s a different kind of approach to assessing your rifle scopes.

In truth, MORE light transmission DOES NOT necessarily translate to better light transmission.

What may be more important is HOW the riflescope manages specific light waves transmitted onto your eye. This is what supposedly gives you better contrast and resolution for low light performance!

We understand how this may feel counterintuitive to what you’ve known so far.

Let’s go ahead and finally address these questions to set the record straight once and for all.

The Bigger Lenses, the Better?

Remember these two among the five essentials?

  • Large exit pupil
  • Large front objective

Would you believe us if we tell you that this isn’t always going to be required?

Large objective lenses indeed need more light passing through a riflescope.

What scope manufacturers don’t tell you is that the low light performance of your riflescope also depends on its MAGNIFICATION.

Let’s Clarify the “Magnification” Part

If the magnification is low enough, then a small objective lens would also be as bright as a larger one.

This is because the exit pupil is EQUAL to the objective diameter divided by the magnification.

The logic shouldn’t feel all that different since this is also how CAMERA LENS work!

  • Reflected light passing through a SMALL HOLE results in a SHARPER image.
  • A SHARPER and clear image can result in a more defined image DESPITE low light conditions. It lets you see more detail.

Keeping your resolution sharp is as important as the inherent scope brightness of the optics.

Yes, a larger objective lens allows more light into the riflescope for added brightness. However, bigger DOES NOT always mean better. Balance your features!

What Does the Main Tube Have to Do with It?

What Does the Main Tube Have to Do with It

Nothing much, really.

The size of the main tubes only matters in relation to the sizes of your riflescope’s optics.

  • The LARGER the main tube diameter, the MORE ROOM for knob adjustments.
  • The LARGER the main tube diameter, the larger the lenses that it can CARRY.

Do remember that larger lenses are also just inherently sharper than smaller ones. This means that the light transmission is assumed to be better.

At the end of the day, the amount of light that exits the eyepiece depends on the magnification of your lenses and NOT the size of the main tube.

Do Lens Coatings Improve Light Transmission?

Yes. Riflescope brightness DOES improve with the use of anti-reflection coatings.

Applying anti-reflection or anti-reflective coatings on your lenses can easily DOUBLE THE SCOPE BRIGHTNESS. Anti-reflection coating does this without all the necessary bulkiness and weight of lenses or accessories… with better specifications!

Anti-reflection coatings achieve this visual marvel through wave phase cancellation.

What Does That Mean?

To summarize this science to you:

  • Raw glass loses 4% of the light that hits and exits through it.
  • This is caused by the air-to-glass interaction that is translated through reflection.
  • The coatings of some earth minerals reduce reflection loss.

Why are these important? Visualize your riflescope right now… You should notice that it has around 10 optics and a high air-to-glass surface area.

Having all of those glass surfaces uncoated lets the light EASILY get reflected against your scope.

How Do You Choose the Best Coatings for the Brightest Scope?

You won’t be able to distinguish through the anti-coating layers using your naked eye.

The only method to achieve this is by comparing the views from each riflescope individually.

This is how an experienced hunter or shooter would test the coats:

  • Find the time to test during low light conditions like sunsets.
  • Point your optics towards a dark shadow or in low-light, and make sure that the sun rays are hitting your optics.

You can finally tell your coatings are working based on the resulting color: there should be LESS orange flare and MORE details in the shadows.

Coatings DEFINITELY have redefined how light scopes work. This development from scope manufacturers is a testament to how brightness does not JUST depend on their sizes.

Our Light Transmission Comparison Verdict

Coat your lenses.

More than this, there are essentially two main takeaways:

  • Having MORE materials doesn’t always result in more gains and better brightness. Sometimes, all you need are new coatings.
  • A scope can only ACCEPT light and NOT gather light.

Some scope accessories are unnecessary and could incur unwanted expenses!

What If I’m Still Unsure?

It should be imperative that you first consult with hunting peers or professionals for what exactly your scope needs.

When in doubt, ask yourself the following questions:

  • Do you really need to improve your brightness?
  • Would it be better to ensure the quality of features such as the riflescope’s durability, precision, or reticle position?

Try to come up with an answer you’ll be content with.

Lastly, riflescopes can transmit SOME of the light it lets pass through, but in no way does it CREATE nor GATHER light.

Simply put: You cannot contain light.

FAQs

#1 Why is the exit pupil important?

#1

The higher the exit pupil (EP), the higher the perceived brightness.

The exit pupil is a result of both the objective lens and scope magnification level. This is essentially the beam of light that exits through the scope’s eyepiece.

You can derive this mathematically by dividing the diameter of the objective lens by the magnification level.

Some examples for a better picture:

  • A 30 mm diameter lens with a 12x magnification gives off a 2.5 mm EP
  • A 30 mm diameter lens with a 6x magnification gives off a 5 mm EP
  • A 42 mm diameter lens with a 6x magnification gives off a 7 mm EP

We can get TWO MAIN TAKEAWAYS from these examples:

  • The LOWER the magnification level, the LARGER the EP = MORE light exiting the scope.
  • The LARGER the lens, the LARGER the EP = MORE light exiting the scope.

These are the two scenarios that arguably result in brighter resolution and color settings.

This also further implies that: the brightness level of a scope does not ONLY depend on the lens sizes but more so on its magnification.

One method you may try doing is turning the power ring on your variable power scope to see how the EP shrinks and enlarges.

#2 What are the limitations of the exit pupil?

Our own pupils limit the exit pupil size.

Having a large EP does NOT always guarantee the maximum amount of light your eyes can receive.

The human eye pupil is MORE DILATED during low light performance times. Your exit pupil size now may be ideal for a regular day hunt, but it will be DIFFERENT when you reach dark or low-light.

Likewise, one large EP of 5 mm diameter exudes a waste of light if the human eye pupil is only dilated at 4 mm.

This one thing doesn’t matter that much, especially if such human eye dilation isn’t normal for you. If it is, you might want to consider downgrading your scope specifications to save on money and resources.

Here’s a professional scenario that we can advise you: TURN THE MAGNIFICATION DOWN.

  • Consider a 42 mm optics with a 6x magnification gives off a 7 mm EP
  • Notice how you can get scopes of a higher power in the market.
  • Ask yourself: do you NEED it? Especially now that you have a recorded 7 mm EP?

It’s enough to know what you need and what your devices offer.

What is Light Transmission?

What is It

Light transmission occurs when light moves through something.

In hunting, light transmission is important since it helps produce the clearest sight picture for you on your rifle scope.

Let’s walk you through the journey of light as you imagine the anatomy of your scope:

  • Light first enters the objective lens.
  • Light is then transmitted through several lenses within the scope.
  • The right amount of light is finally transmitted back to your eye.
  • An image is created to aim your shots, adjust the reticle and knobs, and finally shoot your shot!

As a hunter and shooter, the choice of optics is IMPORTANT because it effectively reflects the light and images back to you for clarity and better low light performance.

What’s important is that you remember why you’re making all of these adjustments in the first place, especially when you’re in low-light.

The quality of your power scope and hunting scopes makes all the difference in aiming at a target and long-range shooting.

Light Management is Key

More importantly, hunters should be more concerned about the light management of their scope optics rather than maximizing light transmission.

This is the best way to ensure the best low-light performance in hunting. Low-light hunting is trickier since, obviously, it’ll be harder to see.

PRACTICE your shooting. Use one or two methods to test which hunter low light performance arrangement is best for you.

Final Thoughts

Final Thoughts

There are a lot of other factors that you should consider when choosing your scopes.

A good indicator would be its low light performance. The comparison of riflescope light transmission factors summarizes this scope’s low-light performance debate by highlighting the importance of:

  • Multi-Coated Lenses
  • Exit Pupil, Magnification, and Objective Lens
  • Size of Lenses and Scopes

Our professional opinion is: Be aware of your needs and device specifications, especially with low-light performance.

Have you hunters encountered any one of these light transmission factors for your riflescope? Has anyone been able to use at least one of the shot improvement methods?

We hope this article helped you out.

 

CHANGELOG:

September 14, 2021 - Reviewed and updated article links

About the author

Christopher Wade

Christopher Wade is a true outdoorsman. After spending most of his career as a firearms expert and instructor in Nebraska, he retreated to the great outdoors to enjoy retirement.

Christopher’s expertise in handling firearms and hunting gear are what propelled him to create the Shooting Mystery blog. He hopes for all readers to gain useful and practical knowledge for enjoying their time outdoors.