View Full Version : How big an Objective Lens do you need?

July 25, 2006, 01:20 PM
Never mind varmints at long range, I'm thinking of deer, on that .280 I'm slowly stalking. Maybe a pig. If you want to make sure you can make a shot very early or very late, on an overcast day when the light's low (and very blue), do you want a large objective? Never mind magnification, this is a different question. I suspect that low light level, rather then great magnification, is the best reason for an objective of 40mm and up. BUT, I've never hunted. So what do you think? What properties do you want, in the scope on the rifle in your hand, when a large buck appears in your binoculars at 200 yards in the last minute of legal hunting hours on an overcast day?

July 25, 2006, 01:38 PM
I've always used 40mm and it has always worked well for me in deer hunting situations.

john in jax
July 25, 2006, 02:02 PM
Depends of the mfg, lenses and coatings. My Leupold 3x9x40mm Vari-X II with the "multicoated" lenses seems to transmit just a little more light at near-dark:30 than my 50mm Tasco world class.But the difference isn't all that much and I'm not sure the cheaper Leupolds with only "fully" coated lenses would perform as well.

I hunt with and have lots of confidence in both of the above scopes. I own other scopes by Tasco, Simmons and Bushnell BUT they aren't nearly as good as my Leuold and the Tasco World Class.

July 25, 2006, 02:23 PM
That seems reasonable - no one has a bad word about Leopold quality. There's a VX-III in the lineup, 2.5 - 7 I think, with a 36 mm lens; I might go that high, in price. Light transmission at low levels is probably too close to 40mm to matter, just a smidge up or down. I wish I could find a user's comment on any of the luxe Leopold glass, the LPS or (more interesting) VX-L series with that interesting cutout; but those are ....ahhhh ..... pricy. The VX-L at 3.5 - 10x is more magnification then I can imagine needing, but being able to put a 50mm lens that close to a barrel has GOT to be useful. So far, Google finds nothing about that lens save retailers' ads, no reviews of usefulness away from the range.

Anybody here do any shooting through LPS or VX-L scopes? I'm curious as heck. And any further comments on the optimal front-lens size for deer in very, very bad light are still very welcome. :)

July 25, 2006, 04:35 PM
First, I have no answer to your real question, but have one of my own to throw in...

Wouldn't a variable-power scope act like a telephoto zoom lens, reducing the effective aperture as magnification is increased, as well as being slower overall than a fixed-power scope with the same sized objective?

In other words, is a variable scope a handicap in low-light situations?


July 25, 2006, 04:44 PM
I have a VX-III with a 50mm on it. In hindsight, I should have gotten a 40mm. The 50 really brings in the light, but sits higher than the 40 would.

July 25, 2006, 06:15 PM
My 22-250's 4.5-14X has a 40mm objective, and I have fired it after sundown at coyotes. It was plenty bright. My 7X57 has a 2.5-7X Leupold VX-I on it, and the objective is 38mm, I believe. I have fired at game 1/2 hour after sundown and thought it was plenty bright. When I took the scope away from my eye and saw how dark it really was, it amazed me! So I think a 40mm objective is probably plenty. The higher the magnification, the smaller the exit pupil with a given objective size. So at higher powers, you might need a bit more.

July 25, 2006, 07:19 PM
I am happy with a 40mm. 32mms are a bit small for me, and the 50mms sit really high.

July 25, 2006, 07:46 PM
tube_ee, I think you're correct. BUT, who is to say that the deer that pops up in the blue ligh minute is going to do so at a particular range? A fixed 4x40, say, would be GREAT if it does so at 150 yards across a cornfield. OTOH if the two of you are looking at each other at 25 yards, if you're hunting a patch where ranges are short, it might be hard to find the deer in a 4x. You do want to be able to set up the scope for the range at which a deer is most likely ... I think. (Zero experience, 100% speculation.)

You've made an argument in favor of a modest range of magnifications ... and a large objective. I suspect that a 2x-5x with a large objective would be ideal for low light deer out to 300 yards, but AFAIK there is none.

Following the threads of adulation on the K-31, since those rifles are apparently accurate, and generally comparable to the .308, it occurs to me that it might be interesting to price out a VX-L on one of those, rather then purchase a .280 first and see what's left over for a sight. Still gotta leave money for reloading gear. I'm off to visit the optics zone, since he posts here and everyone speaks well of him.

July 25, 2006, 07:57 PM
Oh, yeah - John in Jax, the VX-II is my optical baseline. Definitely spend that much, might be willing to spend more. I'm educating myself all at once, on rifles, sights, and reloading.

July 25, 2006, 08:31 PM
Just came back from wandering around the optics zone, looking at rifle scopes.
Yeep. Some of that stuff, the US Optics and Schmidt & Bender ... that can get expensive, can't it?

July 25, 2006, 10:03 PM
Honestly, when I went to look at scopes, I was in a low light condition in Gander Mountain and could not see a difference between the expensive Leupolds and the Nikons. In fact, it seemed that the Nikon was a little easier to find the eye relief, but as for light, I thought they looked equally light, maybe even more so in the Nikon.

I still have yet to see more than buying a name with Leupold though, so I may be biast.

Anthony Terry
July 26, 2006, 02:18 AM
:D theres a thing about light transmission and how much your eyes can actually use, the rest is wasted. the human eye can only take in 7mm of light at the most, usually 5 or 6mm. knowing that, you can divide the objective lense size by magnafication level
ill give an example say i have a 50mm obj. lens and a 3x9 scope. i set it on 6. divide 6 into 50, answer is about 8.5 maybe, dont have a calculator on hand, but this shows that if youre eye takes in only a max of 7mm then the rest of that is not used and not needed. set it on 8 and the number would be6.3 or something which is still alot more than most eyes can take. so if you use a 3x9 50mm scope, the 50mm bell only comes into play on the highest setting.
my point is, you need no more than 42 on a 3x9, 40 is fine
2x7, no more than 36
only time a 50 would really help would be 4.5x14 or bigger but a 44mm would be adequate for a 4x12 and for 4.5x14 on most people.
this is peobably confusing but its true. trust me. scopes dont gather light, they only transmit what light is there. thats where the bigger bell comes into play, but if youre eye cant use it, you dont need it. unless you only use your scope on the highest power.

July 26, 2006, 09:11 AM
VA, I do understand .... interesting stuff. You post at ungodly hours. Make a good surfcaster, no doubt about it.

quack fiend
July 26, 2006, 11:13 AM
my thoughts, after shooting dozens of deer in failing light---3-9 or 2-7x40, quality scope like leupold, nikon, redfield etc. is all you'll ever need, just be sure to turn the scope down to its lowest setting for the last few minutes of light, as this will allow better low-light vision than even your naked eye (at least for me anyways). one more thought, i've never taken binoculars hunting--if you've got good optics on your rifle, why bother? plus if the deer is moving in dense cover you may not have time to fool with binocs. and get a shot off

July 26, 2006, 03:57 PM
for shooting legal hours around here (1/2 hour before and after sunrise/set) a 32 will work fine, but everyone still gets the 40's. oh, and i like the nikon monarchs for the money.

July 26, 2006, 06:38 PM
I took my vx-III with a 50mm objective down to south Texas for hogs a few february's ago. We were hunting at night under the light of a full moon with some scattered clouds. Hunting over feeders at about 100 yards. I shot a real nice boar and I was the only one out of six that could even find the feeder through a riflescope.

Sold me on the light gathering capabilities of large objective lenses.

Although this is an extreme condition, we get some hot weather during deer season and the best chance to shoot something is very early or very late. Its still pretty dark 1/2 hour before sunrise.

July 26, 2006, 07:22 PM
Quackfiend, binoculars would be easier to use for long periods, and would reduce the chance of doing something really, really dumb. I also think suitable binoculars afford the scanning user much better vision, especially at distance, then any monocular lens system could ever do, including better penetration of shadow.

kingudaroad, that's exactly the sort of situation I have in mind .... I know it'd make the collectors beserk to see a K-31 drilled & tapped to accomodate a Warne base and a high-end scope. Still, the price of a K-31 makes makes more money available for good glass. The latent accuracy of the rifle makes a 250 yard bang/flop reasonable for a thoughtful shooter, even a first-timer. For reasons discussed elsewhere, I'm going to be sitting in ambush, not stalking, and I might need to be some distance off from the clearing or whatever that I am surveying.

If I get a brief glimpse of a deer, as Quackfiend notes is certainly possible, I'm not going to take a shot. An ethical beginner should shoot ... thoughtfully.
Like someone said (I wish i could remember where I read this) "Slow is smooth, smooth is fast."

Anthony Terry
July 26, 2006, 10:41 PM
i can see all night on a clear full moon with my 40mm up to about 10x. if you have a 3x9, the 40 will do the same as the 50.

July 27, 2006, 11:05 AM
All you collectors can rest more easily. I've been looking over the general enthusiasm for Darrell's K-31 mounts. Sounds good. Be at ease. :)

July 27, 2006, 03:46 PM
i use a fixed 6x42 leupold and have shot bucks in low light at around 250 yards. so a fixed power scope can do the job.

July 27, 2006, 04:02 PM
My 2 cents worth:

1 to 3 power fixed = 20mm
1.5-4.5 power adjustable or 4 to 6 power fixed = 32 mm
3-9 power adjustable or 8 to 10 power fixed = 40 mm
4-12 power adjustable = 50 mm

But, and this is a big but...getting a scope with expensive coated lenses can reduce the need for size. A good 32mm 3-9 may be brighter than a cheap 40mm. Also there are conditions looking into a sunset when bigger cheap scopes seem to have more internal white-out.

July 27, 2006, 08:04 PM
That doesn't surprise. I have a fair bit of practice shooting near the water's edge (with a camera, that is) at dawn and dusk, situations of inherently high contrast. Coating and other minutiae of lens construction matters a LOT.

Anthony Terry
July 27, 2006, 11:09 PM
definetly, better quality optics go a long ways. what size scope are you wanting to get and whats the average distance youll be shooting?

July 28, 2006, 03:36 PM
I believe a larger objective lens helps on low light, but there are limits as to how much light your pupil will pass. I have had good results over many years with 20mm tube scopes, and only see a down side to those in late evenings. Frankly, I have killed more deer around 10am, than at sunset though, so to me its not really a factor.

Anthony Terry
July 28, 2006, 06:56 PM
alot of beginners buy huge objective scopes not realizing that the eye cant use but so much light. and they sacrifice a lower mount to have a big bell. definetly not a good tradoff. if you dont have a good cheek weld on a heavy cal. gun you will end up with a sore cheek:D

July 28, 2006, 07:21 PM
Anthony, at the moment, I'm just informing myself. I will take no shot beyond 200 yards, unless I have a rest (mechanical, or a well-settled sandbag on a well-placed stump) and a deer that stands still for a silhouette portrait. In that case, I might reach out to 300 - if I'm holding a sight picture well, and I like the picture. As a leg amputee, I'm not climbing trees, or stalking, or going more then a couple of hundred yards from where the horse or ATV drops me off. Neither can I track a wounded animal. More then most hunters, if I do this, I need to set myself up to reliably get that bang/flop.

The best way to deal with a deer's sensitive nose is to be somewhere with some fairly long sight lines, probably farm country or former farm country. That dictates a rifle that's useful out to my 300 yard maximum, and it dictates a scope (so do my eyeballs.)

The K-31 sounds like the ideal poor man's route to an accurate .30 rifle, certainly enough so for the kind of deer hunting I have in mind, and heavy enough that recoil shouldn't be a problem for practice - especially once I've started doing moderate handloads, another new hobby to get into. So ..... right now ...... my thoughts are: a K-31, some Prvi Partizan ammuntion to get started and provide Boxer-primed brass for reloading, one of Darryl's clamp-on mounts, and a scope. A VX-II is the baseline purchase. A good pair of binoculars to monitor my surroundings, orange blaze camo for some idiotproofing, and lots of caution in taking the shot. I can sit quietly for awhile, say, from mid-afternoon to the following dawn. Bang/flop.

I have some experience with cameras. I can see advantages to a large objective that haven't been mentioned in this thread or other threads. F'instance, those yellow Alumina filters that Leopold sells for its' scopes? You can sharpen contrast with a filter that way, but the filter will significantly reduce light reaching the eye, enough to make a difference in marginal lighting. Add the filter to better penetrate haze or dust, or add a grey filter if you're overlooking a lot of snow, or sand. A big enough objective makes the light loss irrelevant. Putting the filter on the scope, as opposed to wearing tinted glasses, means the filter'll be under the lens hood, where it should be to avoid complicating vision with reflections.

The Leopold VX-L would be perfect. It's too expensive to buy if you don't know you need it, but I doubt Leopold can patent the idea of a notched lens. The day it first hit the market, optical engineers at every other scopemaker in the world looked at each other and said "why didn't we think of that? ... it's so OBVIOUS ... now let's do it." Leopold's methods for securing a notched objective group in the lens tube may be proprietary and protectable, but the basic design idea is not. Within a couple of years there will be several different notched-lens scopes on the market, and most of them made with cheap, highly skilled Chinese labor. So, for now, Darryl's mount on a K-31 with a midrange Leopold, VX-II, that I'll purchase used. If I need more then that, I have time to wait.

I'm sure most guys here who hunt will be able to think of times and places where they had to decide to forgo a shot that they'd like to have taken. These are just my notions for how to deal with the problem.

July 29, 2006, 05:23 PM
Some people just gotta have it now!

Anthony Terry
July 29, 2006, 05:45 PM
youre on the right track bro. since you will be still hunting, the heavier gun will not affect you. and it will be easier to steady up on shots. id go with a 4x12 40mm. those k-31's have alot of drop on the stock so youll need to get the scope as low as you can. that will make shooting easier and funner. i really dont think youll need a 50mm bell. but if you want one, then go for it. id invest in a set of shooting sticks if you are sitting while hunting. they will help you out alot, especially hunting in feilds and such. i would really look into a modern bolt action firearm myself. maybe a used remington 700 bdl. maybe in 30-06 or 270. youll would like the feel better id say. k-31 are made for killing people. remington 700's are made for hunting. you can find used ones for 300-400 in perfect shape. you would like the way the stock fits your cheek better i bet. but it is your rifle so do what you want. just some suggestions to help out.

Art Eatman
July 29, 2006, 11:34 PM
Repeating myself again--and again--I think that if low light is an issue, quality binoculars are The Deal. I don't like the idea of somebody using a scope to see whether or not I'm a deer.

I've never had a problem seeing a deer in that last light before dark with a 40mm Leupold, or even with a Weaver K4. The binoculars take care of judging the quality of the deer. Most any old scope will let you hit it.


July 30, 2006, 02:29 PM
Art, I'm not disagreeing in the least. My shopping list, as noted, does include a good pair of binoculars. I have no intention of waving a rifle around experimentally and included blaze-orange to minimize the chance of someone else's doing so, and making a mistake.

Anthony Terry
July 30, 2006, 02:37 PM
shewwee! (wipes forhead) thank god!:D

July 30, 2006, 03:18 PM
Art you've got to admit both the Leupold and Weaver would probably have better coatings than a Wally World Special 40mm. All things being equal a 4x Weaver 28mm would probably be easier to see through than el cheapo scopes.

BTW, Art, I think the question is more how many horns the deer has rather than whether or not it is a deer.

July 30, 2006, 03:48 PM
A scope you might want to check out would be The Sightron 3x9x42 at Midway usa.com for 199.00. The 42 lets in a little more light than a 40. Their 3x10 is good also, but for more $$$.

Art Eatman
July 30, 2006, 07:23 PM
Aw, no argument that a lot of scopes of the El Cheapo variety are, at best, marginal. From comments here over the years, though, dealing with recoil is the biggest problem.

Look: My first '06 scope was a Weaver K2.5. Years later, it was a K4. Later on, I traded into a Leupold Vari-X II, and have mostly stayed with Leupold since around 1970-ish.

I've seen all kinds of scopes show up at hunt camp, and folks seemed to be able to kill their deer. My deal is that I've never had a problem; I guess that's why I don't particularly get excited about it. My father used an old Stith Bear Cub 4X on one '06, and a Weaver K6 on the other. He probably killed more deer than most folks ever see.

Common sense says avoid the El Cheapo stuff, on general principles that you generally get what you pay for. But, if a Rolls Royce type of scope makes for more confidence, go for it! :)

Y'all might have noticed that there's a lot of stuff that I don't get all worried about. :D


July 31, 2006, 05:53 PM
I DID notice that, actually. :) A dollar for every time you heard this discussion, you'd be rich. The hazard of letting NGs like me in is that you get to hear it again.

Anthony Terry, you make a good point about stock fit, and such, and the probable better suitability of a modern sporting firearm. There's food for thought in that ... OK, maybe go check the auction sites again.

Charles S
July 31, 2006, 07:18 PM
I personally believe lens quality is much more important than objective size. I have seen quality 36 mm objective scopes that are much brighter than cheap 50 mm objective scopes.

Fixed power are generally brighter than variable power scopes.

That being stated I would rather have a quality 4X32 scope (Leupold ect) than any 50 mm objective scope made.

I am a deer hunter, not a deer shooter. I find no joy in sitting in a box stand and trying to shoot deer from as far away as possible. I do find great joy in stalking, hunting in the deep woods and being successful.

I prefer a 40 mm objective on a scope of 3-9, but I really prefer a smaller objective. My current favorite scope is 2.5-8X32 mm objective for general purpose hunting. 1.5-6X32 for hunting in the woods.


Art Eatman
July 31, 2006, 10:33 PM
Brian, a primary purpose of this forum is to explain WHY a bunch of us Old Farts have the opinions we do. Sometimes the reasons even make sense. :D If a New Guy can pick up some help, great!


August 1, 2006, 04:19 PM
A suprisingly good low cost scope for late evening shots is a 50mm Tasco Worldclass pluss. Im pretty shure they still carry an over the counter warranty as well. During deer season exspecially in this region alot of nicer bucks are seen right at dusk. Currently I shoot a Kahles 56mm fixed 8 and I love it. The world class pluss I used to shoot is suprisingly close in low light conditions. I reccomend the tasco for the money, and I have compared it with 2 56mm kahles, and a 42mm swarovski. It should surprise you.

August 1, 2006, 06:28 PM
56 mm objective, that's .... big. I think you get a prize for Biggest Deer Hunter's Objective Lens In Thread.

Do you need an adjustable cheek piece to get a nice cheek weld to look through a scope like that?

August 1, 2006, 09:11 PM
No you need one of these.

Anthony Terry
August 1, 2006, 10:50 PM
8x56, according to the exit pupil rule, gives you just the right 7mm of light your eye can use. Most peoples eyes can't even take that. Me, Id rather use a 6x42 with med mounts than a 56mm with tall, very tall mounts and have to crane my neck just to get my eye in focus. :D

Anthony Terry
August 1, 2006, 10:50 PM
8x56, according to the exit pupil rule, gives you just the right 7mm of light your eye can use. Most peoples eyes can't even take that. Me, Id rather use a 6x42 with med mounts than a 56mm with tall, very tall mounts and have to crane my neck just to get my eye in focus. :D

August 2, 2006, 10:19 AM
I dont have any trouble sighting with the 56mm. The rifle is a browning high power with a laminated monte carlo stock. I get a good cheek weld, and the rifle scope combo is extremily easy to shoot. Ive had 4 of my friends kill their first deer with the rifle. Also killed alot of deer running with it. That older kahles is in my opinion the best deer hunting scope I have ever used. When it comes down to a late evening hunts the 56mm is unbeatable.

August 2, 2006, 04:18 PM
I've gotten into the habit of spending more money on my scopes to get better quaility with a small objective. I like to have my scopes mounted as low to the rifle as possible and most the scopes that I'm using now are under 40mm. I have a couple of dedicated varmint rigs that use the 50mm objectives and they are nice but not for carrying on the stalk. I also found that I usually don't use over a 6 power setting on my scopes so that makes it easy to stay down in the small objectives. Most of my scopes are Leupold VXIII in 1.75-7 and 2.5-8, I'm not saying that Leupolds are the best but their optics are clear and bright even in early morning or late evening IMO.

Charles S
August 2, 2006, 04:22 PM
ost of my scopes are Leupold VXIII in 1.75-7 and 2.5-8

That is interesting, those are also my two favorite choices.


August 2, 2006, 07:56 PM
Aaaahhh, one of the new Leopolds. You're the first person I've noted on the Forum to admit to having one. Interesting purchase ... what base and rings do you entrust with that very luxe piece of glass? And (maybe more important) over what ranges are you taking those last-minute-of-light shots?

Anthony Terry
August 2, 2006, 09:08 PM
That VX-L will mount with a Leupold STD base and STD low rings. I like them alot, and have been thinking about getting one for my next varmint rig. I say, if youre going to be using a power more than 8 most of the time, get a 50mm. If you usually keep it set around 3-6 a 40mm is right for you. If you use a power lower than that I wouldnt get more than a 32mm. A 50mm or bigger can come in handy in low light with a long shot, other than that, it's not needed.

Here's a good link to read for picking the right scope. Check it out...

August 3, 2006, 12:20 PM
I have a 4-12 with a 56mm objective. I mounted it on my Sako using Sako extra low rings. The extra low rings can handle up to a 63mm objective, so I didn't have to go with higher rings. So far, I am pleased, though I can't say I notice a huge difference between that and my smaller objective scopes.

August 3, 2006, 07:07 PM
Anthony, the VX-L series doesn't come with any objective smaller then 50mm.
I doubt there's a reason to do so; smaller lenses don't need the extra manufacturing cost and asembly complications of a notched objective lens group. In that series, it's either 50 or 56 mm.

A question for ANYONE with a big objective, 50mm or up, on their hunting rifle.
Aside from the VX-L series, am I correct that the point of an adjustable cheekpiece, as in sniper rifles, is to get your eye up high enough to see through the scope and still get a nice tight cheek weld?

Anthony Terry
August 3, 2006, 09:44 PM
Thats exactly the reason. Cheek weld is everything in shooting, IMO.

And yea, the vx-l is 35.x10 and 4.5x14 50mm only. I was talking about the vx-lonly in the first sentence. After that I was referring to scopes in general. It would be nice on a varmint rig, but anything more than 3x9 40mm is overkill in the woods where you;ll only be using 3x or 4x.