Rifle Scopes sight picture question

[Dantrom]

Is there a way to tell if a scope will have a large sight picture by the specs of the scope size?
I always thought that you could tell by the size of the front bell diameter. I thought it was the larger diameter bell the larger the picture will appear.
But I have a 3-9x40 conquest and a SS 10x42 HD. I thought the SS would have a larger picture seeing that it has a larger bell. But I conquest has a MUCH larger picture. The SS seems to be more consitrated on a smller area.
So is there a way to tell if a scope is going to have a larger picture than another?

For instance the burris XTR 1-4x24 and the burris XTR 1.5-6x40.

http://swfa.com/Burris-1-4x24-Xtreme-Tactical-XTR-30mm-Rifle-Scope-P45510.aspx

http://swfa.com/Burris-15-6x40-Xtreme-Tactical-XTR-30mm-Rifle-Scope-P48170.aspx

I would think the 40mm tube would give a larger picture? I wouldnt think it is something as simple as smaller mag equals larger picture?

Probably sounds like a redicules question, but I honestly am at a loss.

thanks in advance

 

[gstaylorg]

Re: sight picture question

The larger objective diameter has more to do with the amount of light the scope passes. For example, look at the NF NXS 3.5-15x50 vs 3.5-15x56. The exit pupil is different, but the field of view at 3.5x through 15x doesn't change <span style="font-style: italic">noticeably</span> between the 50 mm vs 56 mm objective diameter.

http://nightforceoptics.com/nightforcesc...3_5-15x56_.html

Although field of view is a function of both magnification and focal length of the objective/eyepiece lenses, often it is the change (increase) in magnification that causes the <span style="font-style: italic">most noticeable</span> decrease in field of view (ie. more so than a smaller objective at the same magnification).

The best thing to do is simply look at the field of view specs from the scope manufacturer for which you're interested. Try to think about those numbers in terms of what you will actually be able to see (or not see) in the field of view at a given distance in order to get a better idea of what they mean from a practical viewpoint.

EDIT: Just out of curiosity, how does the field of view compare on your 3-9x40 conquest and a SS 10x42 HD set on 9x and 10x mag, respectively? It would be a more fair comparison if you could set them at equal mag and then see how the fields of view compare.

 

[Dantrom]

Re: sight picture question

seems like I have the same field of view just a considerably larger picture with the conquest.

 

[Jon A]

Re: sight picture question

I think you're talking about "apparent field of view," which you'll see some manufacturers list in the specs in degrees. This is mainly determined by the size (diameter) of the ocular and eye relief.

With a large ocular assy and short eye relief, it's sort of like sitting really close to a big screen TV; the "picture" is big to you, regardless of what's on the screen (no relation to actual FOV).

There are other aspects of the ocular design that go way beyond my understanding that can influence this and other aspects of the way the picture looks, but for scopes that don't list the apparent FOV in the specs, I think ocular diameter and eye relief will give you your biggest clues.

 

[kombar]

Re: sight picture question

It's definitely an apparent field of view issue. I have one of the Leupold ultralight 2.5x scopes on a pistol, and while it has a fairly large actual FOV, it doesn't seem that way. This is due to the combination of a very small ocular lens and long eye relief, which results in a low apparent FOV.

Objective and tube diameters shouldn't have an effect on either apparent or actual FOV.

 

[Dantrom]

Re: sight picture question

Not saying there any issues with the scope, the picture is REALLY clear just not as large as the conquest. I think I see what you guys are saying. Has to do with ocular diameter and eye relief. I don't think I have ever seen ocular diameter ever mentioned in a scopes specs before.
So I'm guessing the only solution is to physically handle the scope and see for yourself!?