Home Forums Hunting & Shooting Ask The Gunwriters Ask John Barsness Questions About "RIFLESCOPE BRIGHTNESS"

Hi Folks:

I want to thank John Barsness (Mule Deer) for providing the Campfire with another exclusive article, entitled RIFLESCOPE BRIGHTNESS, to be found on the Home Page.

Please enjoy, and then please use this space to ask John questions about RIFLESCOPE BRIGHTNESS.

I hope you enjoy the article as much as I am.

Good hunting!

Excellent article, JB. I always take away something new from your writings on optics. Thank you.

You're welcome! And thanks.

Yep JB, good, succinct, and info packed.

Im gonna get my bud, who loves Hubble Scopes to read it!

I'd be interested in hearing his reaction!

Hi John

A good article. Your analogy of the cardboard tube prompts me to ask myself why eyepiece boots haven't become more popular on rifle scopes. Probably worth a try, especially for shooting in moonlight.

Have you tried them?

Excellent, excellent article, John!

dan,

Yes, I have--and they do brighten the view. Which is partly why many night-vision scopes have them.

A good article but I can't help but notice that every curent euro scope intended for hunting in the moonlight features a 30mm tube,as well as an illuminated etched reticle.

I have few scopes that match the above description and they do work well for shooting wild hogs on clear nights.

And none of my one inch tubes,including the euros work quite as well in this job.

My thoughts are that the euro manufacturers use their best lenses and coatings on the 30mm scopes which they know will be used for low light hunting.

Well thought out and put together piece that hammers urban myths and "snake oil" optical physics permeating the internet.

Thanks, John.

DF

Excellent article John......as usual.......

-Ted

Excellent article!

ruraldoc, I think you may have some of the answer. I also think that some of the 30mm tubes allow the makers to put whatever is holding the glass in place further away from the center of the glass, giving a bit wider space for light, glass and coatings to do their thing.

JMHO.

I'm not sure some of the 30mm erector systems are actually larger than 1" erector systems, just more room for adjustments/more elevation for LR shooting.

Comments on that are welcomed.

DF

ruraldoc,

You're absolutely right, many if not most scope manufacturers tend to use their best glass in 30mm tubes. But that doesn't have anything to do with the possible brightness of 30mm scope tubes. Instead it has to do with European tradition--and that's exactly why so many shooters swallowed the advertising claim that 30mm scopes "allowed" more light to pass through a scope.

Not all the scope manufacturers who make 30mm-tube scope use the best glass, because their customers (who aren't European) are more concerned with elevation adjustment range.

Yes, some Euro-manufacturers now make illuminated reticles for their 30mm scopes, but that doesn't mean illuminated reticles don't dim the view slightly. Instead it means they're making for scopes for the American market, where illuminated reticles aren't outlawed in many states, as they are in some European countries.

And just because illuminated reticles dim the overall view slightly (an optical fact first pointed out to me by a European company, for the reasons I stated) doesn't mean they don't help aiming. Being able to put the bullet where we want to is due to several factors, and seeing every hair on a deer, or every point on its antlers, isn't necessary to aiming. Instead we just have to be able to see the outline of the deer AND the aiming point. If we can see every hair on the deer but the aiming point is vague, then scope "brightness" is useless.

Thanks for the detailed reply,very good information. I know that the limiting factors are the exit pupil and the size of the lenses in the erector tube which are plenty big if they can handle the diameter of the light passing through them.

The question that I have is this, do the larger lenses of some 30mm scopes allow for a larger sweet spot? I know that the optical properties of lenses tend to be better toward the center and poorer toward the edges.

Perhaps it is poor analogy but tennis rackets work fine whether they are regular sized or oversized. But many players pick an oversized racket because it has a larger sweet spot and keeps a ball further from the edge.

There is a little bit of that effect in scope lenses, but it usually affects definition more than brightness.

For years Swarovski used larger interior lenses in all their 30mm scopes and claimed extra brightness, but they also used better glass in those scopes. One major side-effect, however, was a relatively narrow adjustment range. This year they finally came out with "tactical" 30mm scopes that essentially use lenses for 1" tubes, allowing for the extra adjustment so many shooters want these days, and they're just as bright as their larger-lenses 30mm scopes. They also cost around $3000.

Can you recommend any particular ones for a Z3 Swaro 3x10x44?

Most excellent article, J.B. Very well done and to the layman's level.

Thanks!

Don't know of any specifically for Swarovskis. In fact haven't looked for any for a while. There used to be an ad in many of the shooting magazines for them, but I haven't seen one in a while.

This is a very informative article, in typical JB style......easy to read, very well put together, therefore very easy to digest and understand, with no apparent bias. I enjoyed it very much.

Thanks for the article, John.

fwiw:
in addition to longer ER allowing stray light betwixt eye & lens, have noted that sitting in a tree/elevated stand with a clear sky overhead as opposed to a blind with just the barrel protruding and the scope's objective lens inside, definitely impacts the low light "performance."

Also, a matted blue barrel reflect less light back up to the objective lens than a SS barrel.

Found this comparing a S&B Summit with 4" of ER & a Leupold to a short 3.15" ER Euro. The Euro gave a considerably "richer" low light view due to the shorter ER and additionally it was sitting over a blued barrel. Switching the S&B & Lupes off to a matte blued rifle and wearing a cap over the ocular lens brought low light performance right up to par...:)

Very interesting!

Probably a big cowboy hat would help considerably....

Do cowboy hats go up trees?

Only after climbing cows.

Well I wasn't sure, but have never seen a guy in a tree with one on.

Another good reason for me to stick it out on the ground...:)

For a long time I have had a fairly simple test for my scopes. Two part test. When it's past legal shooting time the first question is how far can I see something I might shoot under the best the scope provides. A scope that gives me 200 yards is always better than one that gives me 100. The second question is how long does it take me to decide I can shoot.

The first test "measures" brightness, reticle,resolution and color fidelity one way, The second measures both by comparing how well my brain can make sense of what I see and what is actually being presented.

A scope give you a two dimensional picture with a limited depth of field. When you look at an animal with just your eyes, sometimes your eyes are better than the scope and sometimes not and usually low light conditions will aggravate poor perception. Contrast and color fidelity provide very important clues to your brain.

An example: Hunting under heavy canopy, like in a tamarack swamp here, late on a cloudy day. You see two deer, one facing left, the other right, standing one behind the other. Your brain can have a very hard time making sense of the picture even though you absolutely know you are not looking at a Pushmepullyou escaped from a Dr Doolittle movie. A scope might just make that problem worse if it provides a low contrast shallow depth of field view. Distance judgment when your brain cannot resolve the picture goes right straight into the toilet.

Critical distinctions like body angle probably cause a lot of bad hits and lost deer that people swear up and down were dead solid good hits, and those distinctions are even easier to lose than the example above. The scope must provide not only a bright picture, but one with sufficient color fidelity, contrast and depth of field to help your brain make sense of the picture. And, it must be sufficiently helpful that you can decide to shot, not shoot and where to place the shot in the time the animal is giving you.

Targets are vastly simpler to handle. The are almost invariably high contrast. They are just about always decently lit. They are one dimensional and you never need to worry about their angle. You never have to worry about is it a big target or a small target and you know the range.

Enjoyed the article. Thanks again for what you contribute here.

John, I don't know if this is true, but I've heard that larger lenses are easier to make than smaller ones regarding the grind and curvature. I don't know how much that would help the manufacturer in making internal scope lenses (between 1" lenses vs 30mm lenses) but perhaps that could be one of the reasons that the larger lenses produce a better image, potentially. With some of the mid-priced bino's I've owned over the years I usually liked the image of 42mm bino's compared to 32mm models in the same make and model

That’s part of it, but the biggie is “edge effect.” Most stray light comes from around the edges of lenses, because that’s where it’s hardest to bend, and also where runs into lens mounts. Smaller lenses have more edge per amount of surface, so tend to have more edge effect.

John -- I have a buddy looking for a new scope to use primarily at last light of day to shoot at deer coming into a field. Longest shots would be about 200 yards. He's looking for a "bright" scope.

What scopes would you recommend we look at in the $800-$1000 range?

Sorry not to answer sooner, but was hunting, then having computer problems.

The very brightest scopes all run over $1000. At those ranges really high magnification isn't going to help all that much, and the reticle may make more difference than the scope. I'd suggest a 6x42 Leupold with a heavier reticle as one possbility, but any 3-9x or 3-10x variable in that price range would also probably work fine. It's also may be more important for a particular scope's coatings to match up with his eyes than any tiny differences in actual light transmission.

Sorry to be so unspecific, but just about any new scope in that price range is about as bright as another thesedays.

MD,

"But I was hunting" is all the excuse anyone ever needs to give.

Thanks for the info -- I'll pass it along.

Rick Bin:

I could not agree More.

Two prise's John and Eileen.

Bill

John, Great article it really provides a lot of excellent information related to the manufacture of scopes. Thank you for the great article.

I just got around to reading this article. Great work, John. You provided lots of good information in a manner that was easy to comprehend. Your contributions to the Campfire are greatly appreciated.

Thanks very much!

Good article but I want to mention this thread is titled "RIFESCOPE BRIGHTNESS."

What is a RIFESCOPE?

It's a slightly shorter riflescope....

I very much like the article!

I am wondering how wide the light path is between the lenses (the body of the scope). Specifically, there are old 3/4" scopes that were used for big game. Any more the immediate reaction to a 3/4" scope is: "That is a 22 rim-fire scope."

Noted: You've mentioned edge and total area issues and adjustment issues. Does the 3/4' tube restrict light due to light path boundaries?

I have a couple of old Weaver scopes "J" series that I was told were once considered center-fire scopes. I have one on a model '92 Winchester that works quite well, but I use that rifle mainly for squirrels and rabbits as it is chambered for 256 Win Mag.

john: I just purchased a 300 win. mag. Browning BLR and will start loading and hopefully this gun will shoot decent,i do see an advantage to this gun. I also have read in your book first 5 years of looney news towards the end of the book you prefer straight 6X scopes and yes I agree why a straight power , I am thinking about a new leupold 6X ? is there maybe a better choice ? also your 5 year loonie book was very fine reading that your wife eileen and you have put together in this book,i went with the 3 book deal so I am also looking forward to next two books I purchased. and thanks for the loonie hat too ! pete53

Bugger,

Back when 3/4" big game scopes were common, glass was pretty mediocre and uncoated. As a result, the lenses couldn't "bend" light nearly as well as present glass and coatings, so 3/4" tubes didn't constrict the light-path much. Which is why older scopes were longer for the diameter.

You can tell if the tube is constricting the transmitted light by measuring the exit pupil. If it's smaller than the objective lens diameter divided by the magnification, then the tube is having an effect.

pete53,

In my experience, a 6x Leupold is still a good choice, but other companies also make good fixed 6's. In the same price range, the 6x42 Meopta is a great scope.

Glad you like the books, and thanks for ordering!

I'm confused by the word "smaller". Should it be "larger" instead?

Yes.

John,

Thanks again for yet another factual and comprehensible article.

Best,

Scott

So German glass isn't the best. What makes one scope better than another then ? Swarovski scopes have a better Image than Leupold scopes . Is it the coatings ?

Ironworker,

SOME German optical glass is as good as any made, but so is some glass from other countries. What I'm saying is that the best glass isn't only available to German companies.

It also depends on the particular scope model. Some Leupold scopes are brighter than some Swarovski scopes (which by the way aren't made in Germany but Austria).

As discussed in the article, brightness isn't due just to glass but coatings and other factors.

Thanks for quick reply . What do you think is the best long range varmint scope out there regardless of cost ?

Darned if I know! Maybe a Nightforce, but there are some that work well that cost a lot less. It would also depend on what you mean by "long range."

One of the favorite things I love about "brightness" are guys wearing dark sunglasses at the range.

A rifescope is what Layton uses.

VX 3 1.5-5x vs M8 4x compact. The VX 3 is new (never mounted) and the M8 is a bit older.

With the VX 3 set on 4x, which will be better at light gathering at low ambient light? I have these two scopes in my vault.

I'm a fan of fixed power scopes, but in this case I'm looking at light weight also. With the 4x scope mounted, no ammo, no sling my light weight 280 is under 6 lb.
hunting will be in very thick pine and shots will be ~ 50 yards or so according to my brother who has hunted there for cow elk for a few years. The hunting area is steep.

I have a couple of other Kevlar stocked rifles, 350 RM and '06, both a little heavier than the 280. I'll be taking two rifles, I always do. I'm trying to decide which two rifles I'll be taking.

I'm thinking the 280 will be one of them since It is new to me.

Probably the 1.5-5x will be brighter, because its lenses are multi-coated. The M8 has single-coated lenses, and they're also probably slightly "dinged" from years of cleaning, which happens with older scopes and tends to scatter light.

But the best way to tell is wait until after sunset and look through both of them.

Thanks. Yes I've done that with other scopes and have weeded some out. The old style Redfields made in Denver used to be one of the scopes I've kept. I think I still have one or two. I have a 6x Redfield on a 6mm for instance. But I use that rifle for prairie dogs and as a Antelope back up.

I'll be looking through those two scopes this evening.

Hi MD,

A question about the number of lenses inside a riflescope:

By design, are there or are needed more lenses, for example, in a 2,5-10x variable scope than in a 6x42 fixed magnification scope?

Thank you!

PH

Yes. Variable scopes have more lenses inside the erector tube. Changing the distance between these lenses is what changes magnification.

Thank you, MD. I am searching information about this mater and cannot find any cutaway scope view or drawing comparing in detail this point in variable vs. fixed rifle scopes.
Thinking about this, my reasoning is: the only difference would be the movement of the erector lenses between them in the variable to change magnification (and the other coaxial tube and parts needed to do this, of course). Cannot see the need for more lenses than in the fixed power scope as this also need erector lenses. Am I missing something...?

Thank you for your help, again!

PH

A simple fixed scope only requires one erector lens. Variables require at least three, since magnification is changed by camming the lenses to different distances from each other. (If there were only two erector lenses in a variable, the image would appear upside-down, just as it would in a fixed scope with no erector lens.)

OK! Thank you for your answer, MD!

Best Regards

PH

John: which Leupold 6X? The 36 or 42mm model? Thanks again....

I used to slightly prefer the 6x42, because Leupold started multi-coating its lenses in the early 1990's, while the 6x36's lenses remained multi-coated. With the multicoating and a larger objective lens, the 6x42 was noticeably brighter in dim light.

But since the fixed M8 Leupolds became FX's, the 6x36's lenses are multicoated too, and while there's still a difference it isn't nearly as much. Since the 6x36 is noticeably lighter and slimmer, I tend to use them more often than 6x42's anymore.

JB...correct me if Im wrong but the 6x36 should have an exit pupil of 6mm...a tad more light transmission than 40+ year old eyes are even capable of using. Should be bright enough without going to the 6x42....

Yep, a lot of us lose some pupil expansion as we get older, so the 7mm exit pupil on the 6x42 doesn't help as much.

However, larger objective lenses do provide a sharper image, regardless of our own pupil's size, though the difference between 36mm and 42mm isn't vast. This optical principle is most noticeable in binoculars, especially 10 powers.

Well, I don't know about you guys, but that's why I read the .223 AI thread---to work on my pupil expansion, and keep it where it needs to be.

Interesting the comment about 10x binoculars, John. Can you expand on that a little?

Because of the high magnification for hand-held binoculars, smaller objective lenses are more detrimental to the sharpness of the view in 10x than 8x binoculars.

The reason smaller lenses reduce sharpness is there's more lens edge for the total lens area, and lens edges scatter light. This cuts down perceived detail, partly through reduced contrast. More magnification exaggerates this effect, because it also shrinks the exit pupil, which also reduces contrast.

Years ago I guided for an outfitter in central Montana for a couple of years. This was when I was doing the optics column for Petersen's Hunting, so I had several binoculars to test, while we did some pre-season scouting, among them a Simmons 10x50 porro prism that as I recall retailed for $50. The outfitter wasn't much of a glasser--like many guys who grew up hunting in eastern Montana, he preferred driving closer.

But one of his previous year's clients had given him, as a tip, a 10x20 Zeiss pocket binocular. He was extremely proud of it, but that didn't last long after I showed up, and the 10x50 Simmons not only provided a much brighter but sharper view.

In my experience, any 10x binocular with an objective size less than about 40mm suffers from this effect, even the very best. I haven't ever looked through a 10x30 or 10x32 that provided as much detail as the same company's 8x30 or 8x32, even when rested very steadily, and perceived detail is why we use binoculars. I do prefer 10x over 8x for open country, and sometimes even in woods, but all my 10x binoculars have at least 40mm objectives, and one has 50mm's.

thanks John

I recently looked through a Swarovski and was amazed by how bright it was. It was almost like having a flashlight in your face, that was at 100 yards. You can still see the target.

Dang, you're smart about all this stuff, JB!