Sorry about the title. After 15 minutes of thinking, I could not come up with anything better.
So guys (Henry, Kevin, Frank, Steve et al), I would like to ask you a couple of things that are a bit puzzling to me.
Let's begin with apparent field of view. We all know how to compute it roughly by multiplicating the magnification with the true field of view. And I am a big AFOV fan. A big AFOV provides a "Wow!" experience and simplifies the targeting.
I can't really see the need for pinsharp edges if the downside is a narrow TFOV/AFOV.
Anyway, it is not a secret that a couple of my bins have an AFOV of about 56 degrees. I would have wanted more but I can handle it.
The thing is, I use eyeglasses most of the time, and occasionally contacts.
When using glasses, and the eyecups are down, I have a feeling that the AFOV is greater. Of course it is not, but the "Wow!" comes when using glasses. When eyecups are extracted, and that wide black rim surrounds the image, I somehow get a feeling of tunnel vision. And reversely, when the eyecups are retracted so the rim appears thinner, the field seems to widen.
This leads me to thinking, if the ocular ends of the binocular's barrels are as thin as possible, and the exit pupil as large as possible, and the eye-relief generous, the "Wow!" experience would be granted. The "real AFOV" is easy to compute, but does it necessarily express what the perceived vision through a given binocular is like?
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The other thing I would like to make a comment upon is about the speed of the focusing knob. Here and elsewhere, it is defined in terms of "one and a half rotation from closest focus to infinity".
The problem with this generalization is that binoculars have different closest focus. And the closer, the close end of the knob rotation needs increasingly more space.
My Minox is a fast-focuser with only one full rotation from close to infinity, but it takes a few "jumps" with the finger to reach infinity. (The depth-of-field is quite shallow in this model)
But my Vortex can focus a lot closer, and needs something like 1,25 rotations from closest to infinity. Its depth-of-field is tremendeous however, so in real use, I rarely move the knob more than about 50 degrees, which is easy to do without "jumping" with the index finger.
I believe that a more veracious description of focusing speed would be obtained if we settled for a close focus of 3 m/10 ft, and then how many degrees of turning it takes to get the first sharp focus on infinity. That is, for binoculars with deep depth-of-field, when focused to the hyperfocal distance.
For binoculars with shallow DOF, it will take more turns to reach infinity.
The eyesight, pupil size and age of the individual tester will probably make some difference here but I guess the results could be made quite reliable if there is a reference binocular involved in the game.
Waiting for your gathered wisdom to comment upon this.
Kind regards
/L
I think the point is well taken. I really have no real idea of just how to address it. People are different from each other and prefer different things including binoculars. I do tend to think that people tend to obsess way too much about certain facets of "comparative binocular analysis". I tend to think that most people would be far better served to take a few binoculars from a list that you compile however you compile it. From reviews and comments here, from observations of friends binoculars, or observations from a store and if one suits you, the just get it and use it. The thing is that wondering if a brand x would be better than my brand y will usually just drive you nuts.
As far as focus speed goes, I have binoculars that go from a silky smooth fast one turn or even less to 2+ turns. Some go clockwise, some counterclockwise. I have no preference and could care less. Give me a few minutes and the thing is ingrained and I get along just fine. But users really like some certain point on the focus continuum. So yes you are probably right in that the focus should be defined in terms of particular distance parameters. Also close in birding with some butterflies thrown in for good measure is a different need set than waterfowl over some distances.
I really pay no particular attention to AFOV (just goes to show everybody is different), other than to pay some lip service to if it is wide angle or not. I can take 50* or so AFOV just fine, 60* is about right and much more than that seems superfluous to me. Get the field too wide and other things like pincushion, edge sharpness, and field curvature become more problematic. I also do not need glasses with binoculars despite having 62 year old eyes. I will use linear FOV more as a measure, but the thing is after a while you look through enough binoculars that you can get a pretty rapid "go or no go" determination, not necessarily a final performance grade, but is it good enough to warrant further inspection. It sometimes takes quite some time to sort out just what it was that caught your attention. Sometimes it is more obvious. AFOV in combination with some other aspects of the image presented may well be part of it. Sometimes other things beside AFOV will win the day, who knows. I have the idea youi never can tell just how one particular set of eyes will react to any particular binocular.
You will also never get a perfect binocular. They are kind of like your friends. They all have faults. So when you get a new binocular see if you can live successfuly with its strengths and forget about weaknesses, unless glaring. There is a process everybody goes through to get to the point where you feel somewhat comfortable with what you buy. I have a bunch of stuff for sale and am reducing my stable to maybe three or four. I still look at anything I have never seen before, but am far less inclined these days to make a deal on a new one. But I have no doubt something is out there that will reach out and grab my attention.
Hey, I have been out of the loop for awhile so my own part of the "collective wisdom" won't amount to much. If this was a year ago I probably would have more to say.
For starters, yes, you can use the magnification times the degree field of view equation to get a rough estimate on the anguler field of view. If I remember correctly though, based on a conversation that Kevin and I had, the lower you go in the magnification range (7-8x) the less it is accurate. There is an equation to determine the true angular field of view. Kevin probably knows it.
As for a general comment on that issue, yes, I do prefer a wider angular field of view to a narrower one. I love the Nikon E II 8x30 and the Zeiss 7x42 FL because of this. Their true fields of view are huge for their respective powers. This coupled with the depth of field gives the user an extremely satisfying viewing experience.
To touch about what you were trying to relate about eye relief, eyecup/ocular edge diameter, etc... I think I know what you are referring to. I think of the Meopta Meostar with this one. The ocular lens is huge and the rim around it is fairly small in comparison. It has a nice walk-in view because of this and, with reference to the 8x42 specifically, the huge true and apparent field of view make the image addicting.
Eye relief has a lot to do with this. I received a similar impression with the original Nikon Venturer 8x42. It has a large ocular lens and fairly narrow rims on the eyecups plus it has very generous eye relief. Also worth noting is that both bins utilized field flatteners in the design which makes the edges nearly as sharp as the center. All of it contributes to the "experience".
As for focusing speed....I don't really have a preference. If pressed I would say I prefer at least one turn. Focusing tension is much more an issue with me. I prefer there to be enough resistance in correlation with the focusing speed....and it needs to be consistant in both directions.
Hope this helps some.