Rifle Scopes in low light conditions....?

[offroadr1]

which is more benificial, a larger objective diameter or a larger tube size. i have a friend who is dead set on getting a ziess conquest 3x12x56 simply for the larger objective. but im curious if she is barking up the wrong tree. her family has quite a bit of land that they hunt regularly so this would only be used for hunting purposes. she has another rifle with a ziess conquest 3x14x50 that she is happy with, but is convinced the larger objective will benifit her more in dusky dark situations. the guy at the sporting goods store wants to push a scope with a 30mm tube instead of a 1" tube. which will have more impact and provide a clearer picture in low light conditions, a larger objective or a larger tube diameter?

 

[ccoker]

Re: in low light conditions....?

30mm tube allows for more internal adjustment
period

glass and coatings are what's the most important

bigger objective (assuming the same scope) will be a tad brighter at the highest settings

if the Conquest 3-14x50 is not bright enough or have enough resolution, go to better glass...

If she is shooting in such low light she can see the animal but is losing the reticle (say she has the standard Z Plex reticle) a bolder reticle like a #4 or better yet, a GOOD illuminated reticle with nothing more than a small dimly lit dot and great glass will help...

Perhaps she should look into a Trijicon 2.5-10x56 Accupoint
Glass on par with Conquest and a perfect ill reticle system

If she wants to drop big coin, then S&B, Swarovski, Zeiss illuminated reticle scopes should be on the list.

Whatever she does, don't go down in glass quality just to get an ill reticle!
Nothing worse than a poorly done ill reticle scope

 

[offroadr1]

Re: in low light conditions....?

to clarify, she is very happy with the 3x12x50, but has passed it on to her daughter. if that was not the case she would still be using it. i think she is just hoping to get a slightly better edge with the larger objective since she is going to make a new purchase. i was just curious if what the gun store guy had any truth about the tube size allowing more light to enter.

 

[ccoker]

Re: in low light conditions....?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: offroadr1</div><div class="ubbcode-body">to clarify, she is very happy with the 3x12x50, but has passed it on to her daughter. if that was not the case she would still be using it. i think she is just hoping to get a slightly better edge with the larger objective since she is going to make a new purchase. i was just curious if what the gun store guy had any truth about the tube size allowing more light to enter. </div></div>

gotcha
according to everything I have read, no
and the Conquest series are all 1" tubes
to go to 30mm she would have to step way up in price in the Ziess line... then she would have a better scope

 

[Nostradumbass]

Re: in low light conditions....?

I think the magnification power makes as much difference as the objective......what I mean is the more you crank the magnification, the darker it gets. I have a S&B 5-25X56mm and at dusk, I can turn up the power, and it's like turning the lights out.....just my .02$
Phillip

 

[bward]

Re: in low light conditions....?

Here's how I understand it. The exit pupil of the scope determines how much light your eye picks up. Exit pupil = objective diameter / magnification.

 

[deadly0311]

Re: in low light conditions....?

in a perfect world the bigger the objective, the less light you can shoot in with the higher magnification.

You dont with both scopes the 3-12x50 and the 3-12x56 i doubt you will see a huge noticeable difference of shooting time when it gets low light.

Dawe's Limit explains this....

http://en.wikipedia.org/wiki/Dawes'_limit

 

[offroadr1]

Re: in low light conditions....?

so she likely wont see much of a difference if any with the 56mm over the 50. but the tube diameter isnt costing her anyhting either. since the ziess is a 1" diameter, store guy was suggesting a 30mm tube and said it could allow her another 15 minutes of hunting time. lol

 

[deadly0311]

Re: in low light conditions....?

the tube diameter has nothing to do with. All that will gain you is a little more adjustment range.


Ask the guy where in the scope the focal length is set and see his reaction......either will serve fine, the only way she would see a drastic (15-20 minutes) difference would be going to the 72mm Diavari

 

[264win]

Re: in low light conditions....?

never owned or been impressed with the zeiss conquest scopes , but on some optics it apears to my eyes that a larger main tube size helps both light transmission and field of veiw . perhaps you can vist a store that has both around dusk and see what you think

 

[doc76251]

Re: in low light conditions....?

As was said:

The coatings make all the difference in the world in low light (or any light) as to what the eye can see and the brain can register.

The exit pupil is a factor of Objective Diameter / Power. That being said the human eye can only handle an exit pupil of about 7mm before it starts to constrict and over ride it. You can have an exit pupil of 12 or more but the eye (pupil) will constrict to reduce the amount of light and therefor the "picture" sent to the macula (the place where you see at). When you get too much constriction the loss of vision become exponentially because the cell receptors for night vision are mostly located on the periphery of the macula.

Most scopes on the market today will transmit more light to the exit pupil than the eye can use. The coatings are what make that light usable to the brain.

Cheers,

Doc

 

[dcjs]

Re: in low light conditions....?

When you have two variable scopes with different size objective lenses, the bigger objective will allow you to use a bit more magnification in low light, that's all. Assuming your eye pupil opens to 6mm when adapted to low light conditions, a 56mm objective will allow you to crank magnification to ~9,3x without the image getting dimmer, while a 50mm objective will a low a magnification of ~8,3x. Since more magnification means more resolution of detail, the image with more magnification at the same brightness allows you to see more detail of the target.

Below those magnifications, the image will be equally bright with both scopes, only the one with the bigger objective will allow a little more error when aligning the eye pupil "inside" the bigger exit pupil of the scope, making for an easier sight picture.

As has already been mentioned, tube diameter does not play a role in this, the fact that the more low light-capable scopes tend to have bigger tubes is more of a coincidence due to other factors (reticle adjustment range, FOV in variables).

Dawe's limit is about diffraction limiting the theoretical resolution of an optical system depending on aperture, it has nothing to do with the subject at hand.

 

[deadly0311]

Re: in low light conditions....?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: David S.</div><div class="ubbcode-body">When you have two variable scopes with different size objective lenses, the bigger objective will allow you to use a bit more magnification in low light, that's all. Assuming your eye pupil opens to 6mm when adapted to low light conditions, a 56mm objective will allow you to crank magnification to ~9,3x without the image getting dimmer, while a 50mm objective will a low a magnification of ~8,3x. <span style="font-weight: bold">Since more magnification means more resolution of detail, the image with more magnification at the same brightness allows you to see more detail of the target.</span>

<span style="font-weight: bold">Dawe's limit is about diffraction limiting the theoretical resolution of an optical system depending on aperture, it has nothing to do with the subject at hand.</span> </div></div>

It most certainly does, theoretically in a perfect world the bigger the objective the better the resolution. Also going with that, the bigger the objective, the higher mag range can be used with less light to gain more resolution......am I wrong?

 

[dcjs]

Re: in low light conditions....?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: HDC-Deadly</div><div class="ubbcode-body">It most certainly does, theoretically in a perfect world the bigger the objective the better the resolution. Also going with that, the bigger the objective, the higher mag range can be used with less light to gain more resolution......am I wrong?</div></div>
Edit: After refreshing my memories with some reading and putting some more thought into this I'll have to conclude that diffraction plays <span style="font-weight: bold">no</span> role at all here, not even a minor one. As long as you can crank your magnification higher (in good light) and see more detail, resolution of the image presented to the eye is not limited by diffraction at a certain magnification. Since we are talking middle of the road magnifications here, the point is moot anyway. Imagine the resolution of a 6-24x56 scope was really limited by diffraction at 8x (with a resultng exit pupil of 7mm as a reference for night shooting, the situation we are talking about here). You wouldn't be able to resolve more detail by turning the magnification higher even in daylight, which is obviously not the case.

Since this is approach at an explanation is much more to the point, I deleted my previous attempt.