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is there an optimal eye relief ???

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/15/2007 at 08:42
rooshooter View Drop Down
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i'm not asking this in reference to recoil but rather field of view. i've just bought a new scope with 4" of eye relief and a 44mm objective, and yet the sight picture is smaller than another scope i have with a 42mm objective and something like 3.5"-3.75" eye relief.i expected the larger objective to give me larger field of view. this maybe a newby question but is field of view directly related to eye relief? [both scopes have large european style oculars.] can't you have both long eye relief and large field of view?




Edited by rooshooter
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/15/2007 at 09:32
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There is a term used by some optical engineers called the "optical triangle" that probably best answers your question. The triangle consists of eye relief, magnification and field of view. When you increase one side the others decrease. For example, Leupold's have longer eye relief than comparable scopes and tend to have a narrower field of view. In my experience, the size of the objective len's contributes less to field of view than eye relief design. Larger ocular (eye piece) designs do allow for increased field of view in general. Hope this makes sense.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2007 at 05:08
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so would it be fair to say that shorter eye relief always means greater field of view---given that the magnification is the same and the ocular is the same size?

hence my original question---is there an optimal eye relief length for good field of view while maintaining good non-critical eye relief? once again recoil isn't an issue as i'm using a 223.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/16/2007 at 10:51
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as the generalization becomes more accurate it looses more definition in the specific, it always depends on the required magnification, as an example a scout scope set will always give the most eye relief.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 00:16
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I generally think that people should consider to have the correct stock fit and learn how to use the gun instead of having longer eyerelief as the price for eyerelief is narrow FOV.

Leupold have in my opinion totally failed when it comes to eyerelief as they have a non consistant eyerelief that is variable and follows the magnification.

I am mostly using european scopes and short eyerelief.

 

Regards Technika

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 05:24
rooshooter View Drop Down
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technika, how short eye relief are you talking about. is there a point if you go too low where the eyebox is too small and you find it hard to acquire the full screen easily?[ by eyebox i mean the zone in which you can see the whole picture through the scope-related i believe to eye relief as the longer you go the more forgiving or less critical is the eye relief which all amounts to bigger eyebox].

back to my original question then. can you give some ballpark figures where the field of view is good and the eye relief not too critical? say 2.75"-3.75"??

on that topic then, can one tell by simply looking at a scopes eye relief figures on the internet whether the view through the scope is going to be pleasing when the scope is bought and arrives on the door step?

lastly, is the sight picture that i see when i put my eye to the scope[the size of the circle]engineered into the scope??? i ask this because as i move the magnification from lowest to highest the circle size doesn't change even though the field of view does. therefore what i really want to see is a big circle and a large picture not necessarily a large field of view. is this a correct understanding??
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 08:06
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technika wants a shotgun mount in a rifle and it ain't going to happen with any combination.

technika have you put yourself on a timer as to mounts (mounting the gun not scope mounts) and timed shots, to see if it is slower or is it a just a personal preference?? (which is ok, it just needs to made apparent).

rooshooter -- do you shoot with both eyes open? I'm glad to see you are using more qualifications so the topics can be addressed.

 

on that topic then, can one tell by simply looking at a scopes eye relief figures on the internet whether the view through the scope is going to be pleasing when the scope is bought and arrives on the door step?

generally no because the scopes never mount up, the same on the gun, such things as bolt clearance, etc. generally euro type scopes "stick out the end" to much for americans. (which increases with mag. range with any brand).

 

the what you see is what you get aspect of scopes is a result of not a we want this. A zeiss I have certainly changes the size of the "circle" as magnification is changed. (size of picture gets smaller). Is this what you mean?

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 10:54
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what i mean is this.if i have two scopes;one a 4-12-42 with eye relief ranging from
2.7"-3.1" and the other, a 5-20-44 with eye relief ranging from 3.2"-4.7"..........

if i put both of these scopes on 10x the picture that i see[field of view] is still going to be bigger on the scope 4-12-42 because that scope was engineered with shorter eye relief and greater field of view correct???

to clarify what i was saying about the 'circle' being different to the field of view. i said that because it appeared on first glance that the circle didn't change as the x was changed...on closer examination it does seem to change size ever so slightly. so all along i guess the sight picture[circle] i've been raving on about is plain and simple 'field of view'.

i was asking about good ball park figures of eye relief and that i now see is dependent on whether the scope is fixed or variable and magnification.my 5-20-44 with eye relief of 3.2"-4.7" has smaller field of view than i would ideally like....however on 20x there is still good non-critical eye relief which can't be said about many other high power variables, and i mostly shoot on 20x. so i quess what i really want to know is, how much less than 3.2" can one go before things get too critical???
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 11:23
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Roo, 3.2 of eye relief should be acceptable with up to a 300 win mag. If your shooting posture is correct. I know of two people shooting 300 RUM with only 3 inches of eye relief, They do shoot all the time though, and their posture is nearly flawless.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 18:02
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maybe this whole 'long/non-critical eye relief' thing is over rated. if posture/cheeckweld is good, having a short critical eye relief shouldn't be a problem.true???
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/17/2007 at 18:13
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does 1 metre of field of view at 100y translate to that much bigger a picture i see through my scope??? i'm comparing a zeiss conquest 6-20-50 with field of view of 5.8'@20x@100y to my monarch 5-20-44 with 5' of field of view@20x@100y.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 07:06
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I think it's important to have good exit pupil for close hunting, and in general moving targets which we see as hunters, A forgiving sweet spot if you will. In these instances cheek weild is often not good any way, unless it is practiced alot, and becomes automatic.

A good forgiving exit pupil will mean other compromises, FOV is one of them, as is eye relief. the intended application of the scope is where you determine which is more important.

Most hunters need eye relief, exit pupil and field of view. so manufacturers make sporting scopes to accomodate you will find there are all manner of theories as to which is more important, thus all manner of combinations to choose from.

Which is more important to you will often dictate your scope of choice. this is why (one reason any way) optics are so subjective.

Once you know which of these are the most important to you for your intended application, you can then choose the scope you would most enjoy using.

Exit pupil gives you 2 things 1 forgiveness, and 2 lowlight use, (Glass quality not withstanding)

Field of view allows you to see more of the surrounding area Important for moving targets, and proper lead.

eye relief well thats obvious, no one likes cuts and black eyes.

All are related to power, lens diameter, scope size, and all the various formulas for the grinding of the lenses.

Being an Engineer I have a natural curiosity towards designs and have looked into some of these things you would be amazed, Building and designing Bridges is a piece of cake compared to the optical science. 

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 07:22
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thanks. most helpful. though you leave me a ittle confused. you speak of exit pupil which i thought has to do more with objective size than anything else. but you also speak of a forgiving sweetspot that sacrifices eye relief, when i thought the long eye relief is what gives good forgiveness?? maybe you are speaking about another aspect of the same topic that i'm unaware of?? please go on to explain, or anyone else reading this.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 07:43
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Oh I forgot, You may or may not agree here, but the additional .8 in the field of view is really moot as at that magnification for hunting atleast, you wouldn't need it, just back down on the power ring, for a moving target. For most people 100 yrds for a moving target is a good shot. much past that and you run the risk of wounding the intended quarry. so 20x would be way too much mag. 4x, or 5x is plenty at that distance. 20x should be your mag for 500 yrds and more, unless you're  target, or bench rest shooting, in these applications FOV is not necessary, nor is exit pupil a big concern here hence the huge power zooms that they employ.

 

Yes it is true longer eye relief is related to exit pupil, which is related to ocular, and objective ratio, and is limited by the power whether variable or fixed.

As I stated all are related, and can get confusing. There are several things involved. Focal lengths, Grinding prescription, etc

Eye relief is related to focal length, which when designed into a scope determines alot of other things.

Exit pupil is determined by lense diameter ratios, and the designed magnification range.

 

All are limited by the scope size which will detrmine the maximum in any one of these areas, due chiefly to the necessary focal lengths to obtain certain aspect ratios.       

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 08:22
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 08:35
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thanks.sounds complicated but helpful all the same. cheers

Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 08:38
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/18/2007 at 08:39
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I hope this helps friend, and yes it is complicated designing bridges is easier
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 09:05
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is the image i see through the scope[be it any scope], the same as field of view?

or to put it another way, can two different scopes, both 3-9-40's, both given the same field of view stats, appear different to look through...the image in one is bigger than the other?? and if that is the case one really needs to look through a scope before one buys to know what they'll be getting[seeing] true??
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 12:54
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Let me see if I can simplify some things for you.  The image you see through a scope is not the field of view, but has a FOV that can be measured.  Two scopes, will say 3x9 40 mm scopes can have different FOVs, as their internal lenses are goint to be different.  Finn talked about the optical triangle, so various things can affect the FOV.  Magnification makes the FOV smaller, as you are presented with a smaller portion, or will say a cropped and enlarged portion, of your initial image.  Of course if you measure that FOV from your original image, it will be much smaller.  Objective size affects the FOV, the larger, the smaller the FOV.  Hope this helps.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 13:17
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FOV is nothing more than the width the viewable image spans at a given distance and at a given magnification and is, in fact, the full extent of the image you see in the scope.  The objective size does not affect the FOV; the ocular size and focal length does.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 17:21
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Ted, actually, the larger the objective, the smaller the FOV.  The difference, compared to other variables may not be as great, but it is true.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 17:43
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doliphin, or anyone else, please explain how a larger objective yields a smaller field of view???
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 19:11
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I sure hope the Dark lord comes around but I belive FOV is determined by the magnification and the focal length of the ocular lense.

I think what both Ted and Roy say have merit. Though, the radius of curvature of a single lense has an effect on focal length, too. This may not come much into play regarding the thin lenses in scopes.

 

http://opticstalk.com/forum_posts.asp?TID=80&KW=fov+diam eter&PN=0&TPN=1

 

http://opticstalk.com/forum_posts.asp?TID=5556&KW=fov+di ameter&PN=0&TPN=1



Edited by tahqua
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: October/23/2007 at 21:07
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Frankly, I would like to know how a larger objective lens reduces FOV. I have heard that one, but it doesn't make a whole lot of sense to me. Pretty easy to compare specs to find out if that has merit or is boulder dash.

 

Roy

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