Home Forums Hunting & Shooting Hunting Optics When does 50 mm + objective become useful?

As a younger person I thought those big 50mm scopes were ugly and unnecessary. These days I'm using a Zeiss HD5 in 3-15x50 as my go to hunting scope and can't imagine going back to a 40mm given a choice. I still shoot targets and varmints with down to 32mm scopes but for hunting bigger seems better now.

I like the 50mm VXIII’s by Leupold.

Perhaps this is most people's experience. I compared Swarvoski z5 5-25X52, Leupold VX-6 4-24X52, Bushnell 6500 4 1/2-30X50 side by side on deer antlers at 131 yards. They all went down at the same minute. Then on another day I compared the 6500 with the new Leupold VX-5 3-15X56. The VX-5 lasted six minutes longer than the 6500.

On another evening I compared a Swarovski z8i 2.3-18X56, Swarovski z6 5-30X50 and a Bushnell 6500 4 1/2-30X50 side by side. The z6 went down at 7:13PM, the 6500 went down at 7:24PM and the z8i lasted until 7:44PM. That means the z6 went down eleven minutes before the 6500 and the z8i lasted an additional twenty minutes. The owner of the two Swarovskis told me, "I knew that z6 wasn't very good."

The z6 and the first three z5's I bought proves beyond a doubt one doesn't get what one pays for.

A large objective diameter has two useful effects:

a) it increases the size of the exit pupil of the riflescpe
b) it increases the theoretical resolution of the riflescope

The effect (a) in turn does two things:

(a1) It gives you a larger more comfortable "eye box" behind the scope so precise eye position becomes less critical.
(a2) It provides a brighter image at dawn or dusk if your eye pupils enlarge enough to be able to use the wider exit beam.

To me, the effect (a1) is the most desirable for hunting. It makes it very easy to look through the riflescope and acquire the target. Effects (a2) and (b) are good to have too. If you have a high-power scope (say more than 10X), then you do want to have a large 50 or 56 mm objective so that the image resolution is sufficient. With power more than 20X, the air turbulence effects become so noticeable that adding more power or more objective diameter doesn't add much to image quality. Also, hand shake becomes very distracting.

In the good old days, the diameter of the exit pupil of a riflescope was it objective diameter divided by its magnification. With the advent of large zoom-ratio scopes such as Swarovski Z6 and Z8, this is no longer true. At low power, the internal apertures limit the light beam diameter passing through the scope so, for example the Swaovski Z8i 2-16X50, has an effective aperture of only16.3mm at 2X so it is actually a 2X16 scope at its low power!! As a result, it only provides an 8mm exit pupil at 2X. For comparison, a 2.5-10X50 Zeiss Varipoint riflescope provides a 15mm exit pupil at its lowest power, making it it a much "faster" scope for shooting at running game at low power.

While the extra zoom ratio is loudly advertised, the limitation of the internal apertures is not.

-Omid

Omid,

In my last post you will notice the z8i lasted twenty minutes longer than three good scopes; and 31 minutes longer than a Swarovski z6. What do you think allowed this. By the way, both the owner and I agreed when the scopes went down.

I have been able to shoot deer using a Zeiss Victory HT 2.5-10x50 that I would not have been able to shoot using my VX6 2-12x42. The 50mm is worth it to me. In fact, as I am getting older I am considering going to a 3-12x56 for hunting out of blinds or when still hunting.

IMHO the two go hand in hand. You need to be able to safely and properly pick out the "right" target when looking through the rifle's scope. This is important in very low light when transitioning from binoculars to scope when there are more than one animals in close proximity to each other.

I’m curious. Do you think that having an illuminated Firedot reticle would negate the need for a 50mm objective over a 40mm objective? Wouldn’t almost any quality optics of say a 36-40mm be able to resolve the animal enough in low light to make the shot unless we are talking a fairly long range shot?

Hi Rigman,

My comments above don't contradict your observation. The Z8i's exit pupil is sufficiently large for low-light observations at low powers (8mm is still larger than max dilation of human eye pupil) and at high power it will act like any other scope and its brightness will depend on the "actual" objective size. The Z8 scope you tested had a 56mm objective lens compared to 50mm in others. A 56mm objective collects 25% more light than a 50mm objective (lens area is 25% larger) so it will look brighter at medium/high power. What power did you use for your observation? Did you compare all three scopes at same power, say 10X?

-Omid

Ringman, did the owner of that Z6 talk to Swaro customer service about it?

I don't remember what they advertised as light transmission data for that scope, but the current Z6i says 90% and that is comparable to most of their stuff. Interesting that the Z8i is 3% higher.

tomk,

I don't know. He's owned that z6 for several months so I doubt it.




Omid,

As much as is possible all the optics I play with are set on the same magnification setting. I called Swarovski, Leupold, and Bushnell about the accuracy of their magnification ring settings. All were adamant the numbers are accurate.

The owner of the two Swarovskis was a little late arriving. Since the z6 was the poorest performer we used it on the lowest setting on which we could clearly make out the 13” wide deer antlers 131 yards away. That was 15X. The z6 and the 6500 both have 50mm objectives. And yet the z6 (costing about 2 ½ times more) got beat by eleven minutes.

In my comparing I discovered exit pupil when looking for good low light performance is a joke. Along those same lines I compared my Minox 13X56 (two 56 mm objectives) with my Bushnell 6500 4 ½-30X50 (one 50mm objective). I set the 6500 on 13X. It lasted two minutes longer than the Minox. I traded the 13X56 for a Minox 15X58 (two 58mm objectives). It was so much better I thought it might be as good as the z8i. Not so; although it did beat the 6500 set on 15X by nine minutes. But the z8i (one 56mm objective) lasted eleven minutes longer than the Minox 15X.

No,

I'd trade my Minox i 20 x 56 for a good 40 mm. Don't get me wrong, it performs well. But it's too damned big.

How does tube diameter affect the objective. I like the 30mm tube with a 40mm objective on my Leupold 4.5x14.

Gentlemen:

For the record, as I wasn't clear about this, the comparisons I was referring to were at the same aperture, i.e. the same exit pupil. I get good results in low light down to 5mm area.

IMHO, no, and yes. As mentioned earlier in this thread, using my SWFA 6x42, I could see my "targets" (various darkish objects in the shadows of my yard) but not the reticle. I think that the two problems are separate issues. If anything, a lighted aiming point will make it harder to see the target under very dim light because it will cause your pupil to close a bit. Possibly the larger objective would help overcome that.

The deer I shot moments before legal shooting time ended last year was quite visible at 20 yards or so through the Mark AR Mod 1 1.5-4x20 on my .308 and the green dot, set very low, stood out very well. After the shot, she ran off with the others and stopped about 80 or 90 yards away. At that point, I could see the others well enough that I thought briefly about dropping another one. With my naked eye, the only way I could tell when she flopped over seconds later was by the flash of her white parts. If a 20mm scope let me see that well, I feel pretty certain a 40 would have been even better.

One of the things I often do while waiting for legal shooting time in the morning is checking to make sure I can see my sights. I've always been able to make out my ordinary duplexes in 2-7x33, 4xwhatevers, and 3-9x40s before it was legal to shoot. Until last year, I usually left the woods a bit before the end of legal shooting time for safety's sake, but last year, hunting on private land, I stayed late several times. Again, checking through my scope, I could see well enough to shoot until the final gun, at least in the open field I was watching. A little more light wouldn't have hurt though. If a larger objective helps YOU, go for it.

when does a 50mm obj become needed for hunting? unless its some sort of specialty hunting I am going to say hardly ever. I have been using a 2.5-10x32 NXS compact on my calling rifle the last couple years. seeing a coyote in sage brush is hard even with excellent light, seeing one in bad light well that is really tuff. With the distances you should be shooting at or should I say NOT shooting at. 5 or 6x is all you need your scope at, even with the small 32mm objective its still plenty bright at that power. 5 or 6x with my little 32mm obj I can make a shot on a coyote out to at least 250 yards until its not legal light to shoot anymore.

The one that surprised me the most was my 1.5-5x20 Leupold with the Heavy Duplex. I put it against my 30 mm tube Zeiss & Swarovski 42 mm objective Euro scopes and that Leupold Heavy Duplex stood out well past legal light. The standard Duplex reticle in the Leupold 2.5-8x36 disappears in low light much faster.

And THAT my friends is key. Our own JJ Hack pointed this out to me years ago and a HD really helps to close the gap of superior glass. For example, my Z6's incredible glass, but thin crosshairs, when compared to one of my Leupolds VX3s both set to the same magnification and similar objective lenses (42mm V 40), the heavier X hairs on the Leupold allowed that scope to hang in there and in some cases surpass the Z6, all due to the heavier reticle. The down side to this is of course target fidelity, but it is a tradeoff.

I can't afford alpha optics so getting them with their excellent glass and coatings won't happen for me.

I do have a Bushnell Elite 4200 in 2.5-10x50 that I use on my 270 WSM. I use this where the shots are often 200 yds plus and often shots are closer to dusk than any other time. It has served me very well.

For my eyes, I find that this scope does stay slightly brighter than other scopes of the same price point with smaller objective diameters.

Dan

I wouldn't sweat not buying alphas, as we are talking low light hunting here, not shooting at 1000yds. A great low light reticle in a good scope ought to do. If you are having trouble with the seeing the target as the OP stated, you can pick up performance with some more magnification and an applicable objective to brighten things up without breaking the bank.