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Shallow depth of field in the 8x32 format (1 Viewer)

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1. I don't think that an empirical test showing that the two bins being compared (8x42 vs. 8x32 of the same series) measure the same or nearly the same DOF invalidates Lulubelle's or anyone's perception of lesser of depth in the midsized version.

2. Something goes on between the bin and the observer that can produce different perceptions of depth, and reports of this are too widespread to be discounted.

3. I've mentioned some external reasons why midsized roofs in general could give a lesser perception of depth than their 8x42 counterparts, but my gut feeling is that where the actual difference resides is in the depths or shallows of our brain's convolutions as explained in this short article:

Hello Brock,

Thanks for your many interesting thoughts, this being no less engaging than most. I mean that.

In responding to the first point, my position is that one never proves that there is no difference between two things, be they experimental treatments, performance of binoculars with different glass types, coatings, ...whatever. Why? Because 'no difference' is the null hypothesis, which in my religion of science is only accepted through lack of sufficient evidence to reject it. So, the ultimate question is not whether there is a difference if one looks hard enough, but whether the difference is large enough to be significant. This is the basis of statistical decision theory (of the Neyman-Pearson type.)

Perceptions of stereo depth, can be triggered by a great many visual stimuli and vary considerably between individuals. The real question is whether some of the variability is accountable to instrument parameters other than the ones I mentioned earlier. Lots of people draw incorrect conclusions from scant evidence, which is OK by me. I gave up on religious evangelism when I reached middle age. At that point I figured out that arrogance was a far better approach. LOL

With all due respect to the author, that short article was way, way, way too short, and not quite ... accurate. But I do think your gut feelings are relevant as much of our understanding points to the enormous capacity of the brain, which is not fully understood by any means.

Thanks again,
Ed
 
...When you substitute a camera instead of the human eye, you lose another element in the human-bin optical train, namely, the brain, which processes the data and interprets it.

Oh, I overlooked this point. Yes, I agree. Most folks don't wish to consider the biological side, and for those keenly interested in binoculars and telescopes it's often an annoying distraction. The brain, however, anatomically includes the retina of the eye, and a good deal of data processing is known to occur there. Too bad. It's like talking about a camera without interest in the sensor array. More is being discovered all the time, such as visual "receptive fields" that were only unearthed during our lifetimes. The properties of these biological structures have a great deal to do with the peculiarities of how we perceive, and how we adapt to visual stimulation. End of polemic.

Ed
PS. Delve into this at your peril. http://en.wikipedia.org/wiki/Receptive_field
 
I believe that it has been pretty well established here that Depth of Field is............................................................ ............................................................................................................

Other people will add more information here and it probably will be easier to understand than my comments.

Bob

Oh Well! :brains::h?:

Bob
 
Bob,

I can’t speak for Ed but I believe we both believe that magnification is the overwhelming controlling factor of DOF, he can correct me if I am wrong. We just differ on the source.

Ed, Brock;

A couple of years ago I set out to prove what I was “seeing” with binoculars and other optics.

This turned out to be a rude awakening, at least as far as I am concerned. It turns out that what I see is not all that reliable; I think I see more what I “expect to see” rather than an “absolute” memory record.

Consider some of the following:

1: Studies in eyewitness testimony has become very suspect because of factors such as memory, suggestion and other outside factors. Turns out that eye witness identification in test scenarios is wrong a very high percentage of the time. I will not go into detail, but just one such study by Stanford (http://agora.stanford.edu/sjls/Issue One/fisher&tversky.htm) is linked for reference. I follow this with interest because I testify in court a lot and talk to witnesses of accidents, property cases, industrial accidents, etc as an expert witness.

2: I used to be an avid reader (now days, I pick up a book and immediately go to sleep). When I am “in the zone” in a good book, I see the images in my mind, more like watching a movie. I do not remember the book at all, turning pages, etc. When I think of the story, I revisit the mental imagery, not the retinal image; I have absolutely no recollection of the actual book. I have to assume most readers have the same experience.

There seems not to be much of a correlation of what I actually see versus what I remember and “visualize”.

I am very surprised Brock, as a writer, has not made mention of this before.

3: Consider dreaming. Very clear imagery with no retinal input.

I have come to the realization that I am far more dependent and comfortable with devices that show measured data like light meters, spectrometers, CCD arrays and other hardware that shows, and repeats, levels and values.

They seem to be more reliable than what I “see”, which seems to change with every light level, my mood, or my state of fatigue.

Just rambling, been thinking of this for a while.

Best
 
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Bob,

I can’t speak for Ed but I believe we both believe that magnification is the overwhelming controlling factor of DOF, he can correct me if I am wrong. We just differ on the source.

Ed, Brock;

A couple of years ago I set out to prove what I was “seeing” with binoculars and other optics.

This turned out to be a rude awakening, .................................................

Just rambling, been thinking of this for a while.

Best

Ron,

I agree with you and Ed in your first sentence above about magnification and stated so in the deleted portion of my earlier post.

I was really just making a wry comment about my rather optimistic last sentence. ;) No real criticism was intended. In fact I rather enjoyed the discussion. I hope Lulubelle did too.
Bob
 
Bob,

A couple of years ago I set out to prove what I was “seeing” with binoculars and other optics.

This turned out to be a rude awakening, at least as far as I am concerned. It turns out that what I see is not all that reliable; I think I see more what I “expect to see” rather than an “absolute” memory record.

Best

I think you are on to something here. I think a lot of us see what we want to see. I also am coming to some realization, as I look further that maybe the differences in percieved depth are not as great as they seem if I try to measure them. However, they still look to be there. So I think "percieved" is key, and may be one reason why one binocular is ultimately preferred by one particular user over some others.

I will add something here. I recently got a new Kruger Caldera 8x42. I ordered this one from a dealer. I originally looked at this glass in the Kruger factory which is about a two hour drive north of where I live. I was quite impressed with the one I looked at in the Kruger facility. I was less than impressed with the one I ordered. The two binoculars would have yielded the exact same images as posted by Norm Jackson of the chess pieces. The one I ordered was the second image, the one at Kruger the first. You would never have guessed they were the same model binocular. I wound up back at Kruger with this binocular. It turns out the one I ordered had some issues. One barrel was about 2.0 arc seconds less resolution than the other barrel. The collimation, while nearly within specs, was not real good. I was with the Kruger engineer when he checked this glass out, a pretty interesting experience. This should not have made it through QC, but did (or maybe had some shipping damage). With the binocular I ordered, looking at a tree full of Yellow Headed Blackbirds, you could get any one in perfect focus, but never two. There was no depth of field or focus, however you choose to look at the definition. So I am now wondering if some perceived depth issues may be telling us we have a binocular that is somewhat on the less than spec end of the acceptable spectrum of tolerances.

Issues aside, the Caldera is a very good binocular BTW.
 
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... Just rambling, been thinking of this for a while.

Ron,

A pleasure listening to you ramble :t: (or was I really "listening"? Hmmm.).

The article by Fisher and Tversky was great! Barbara Tversky, incidentally, was the wife of a very great psychologist and decision theorist, Amos Tversky. http://news.stanford.edu/pr/96/960605tversky.html

Many decision theorists contend that an accumulation of circumstantial evidence should be given greater weight than eyewitness testimony. But, I figure that's as hard to sell as the argument that binoculars don't possess depth of field.

I'm sure you and Bob know what I mean. Well, Bob anyway. :-O

Ed
 
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The 8x42s generally have a flatter field, the sweet spot bigger, than the related 8x32. So the depth of field may appear less as the whole picture gets slightly worse. You gain wider field but lose focus toward edges.
 
Hello Ed,

Not being one to take your ideas lightly, I gave more thought to a way to either verify, or change, my thinking.

I came up with the idea of throwing together a simple focus distance collimating lens (being way to lazy to go outside and do all the measuring required) and used a fork with 6 mm spaced tines, turned at an angle to bring the distance to about 5.5 diopters between them. I wanted to keep the spacing larger than the DOF of the bino used, a 7x50 Pentax to make out of focus obvious. With one end tine focused at infinity that made the other tines approximately 8.9 m, 4.6 m and 3 m distances using the lens law. I checked this with the calibration scale left on from a recent review of the bino.

The setup was the fork at the focus of a 50 mm, f:/4 lens, the bino under test and then a frosted glass projection screen in exit beam. This takes the eyes and camera out of the equation. There is only one tube being used, so no stereopsis, and since the image is projected to a flat glass, there should be no visual cues with a distance difference on the back side of the glass, just a flat image. See first picture attachéd, pardon the mess, I worked on a new setup all weekend and piled a lot of stuff on that table and have not finished and got around to putting it up yet.

It took a lot of light to project back to the screen, but believe me, I checked by focusing on each element individually and looked at the out of focus tines. There was great detail in focus because of the large apparent angle at infinity focus which does not show up in the projected image, but the out of focus blurring is consistent. The last picture was focused at about 6 m, about half way between the middle tines (approximately).

Since there is no brain, CCD, stereo effect or 3D artifacts to be processed on the back side of the screen, I have to conclude, at least to myself, that the DOF blurring is coming from the binocular. I feel somewhat more comfortable with my earlier posts now.

Best
 

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I think you are on to something here. I think a lot of us see what we want to see. I also am coming to some realization, as I look further that maybe the differences in percieved depth are not as great as they seem if I try to measure them. .....

Interesting twist, instead of "seeing is believing," the new mantra is "believing is seeing".

From reading the reviews, my expectations of the Nikon 8x and 10x42 LXs were that the views were going to be like the 8x32 and 10x42 SEs - sharp on-axis and sharp at the edges, but with better color saturation and contrast.

When I finally got to try them, they met those expectations, but what I hadn't expected was the severe "rolling ball". I had never even heard of "rolling ball" before, and not one reviewer even mentioned this "funhouse effect" in their review.

Believe me, I don't want to see "rolling ball". I don't like it, but despite trying an 8x42 LX for a month and a 10x42 LX for a month and from my friend Steve's experience, expecting I would adapt, I couldn't stop seeing it.

As we now know from Holger's contributions, it is the property of your eyes that determines whether or not you see "rolling ball". However, from the adaption response some people experience who see it at first and then don't see it, I suspect that for some users it also involves a "trick of the mind".

It's like the famous experiment with putting the upside down mirrors on chickens who adapted to an upside down world. Some users of bins w/out or with very low pincushion see the "rolling ball effect" and then adapt to this steeply curved "world" until it looks normal. Others like myself can't make that adaptation.

With the 8x32 LX, I was expecting some "rolling ball" and a similar level of 3-D perception as the 8x42 model (which was decent in that regard for an 8x roof), but neither of those expectations panned out. The midsized model had enough pincushion to make the "rolling ball" a non-issue for me, but the image was so compressed that it was like I was transported to Flatland.

When I got out the yard stick and measured the DOF in the 8x32 SE and 8x32 LX, I found to my surprise that the two bins were a lot closer in DOF than they appeared to be while looking through each bin.

Unlike at the quantum level, the act of measuring didn't introduce uncertainty. The view through the LX still looked just as compressed and 2-D as it did before I measured the DOF. Perhaps a less pig-headed person's perceptions might have changed, but for me, the "song remains the same".

Going back to my post about how the brain interprets visual cues, the cues from the 8x32 SE and 8x32 LX vary in this manner...

1. 8x32 SE. Objects in front or in back of the target are blurry but not totally out of focus, and it takes more focus travel to get them in focus than it does with the LX. It is easy to see the "space" between the objects in front of in back of the target.

2. 8x32 LX. Objects n front or in back of the target are very out of focus and in some cases unrecognizable. However, just a tiny movement of the focuser one way or the other brings those objects in the foreground or background into focus. There seems to be very little space between the objects in front or in back of the target, as if they were very close together. Reminds me of the sticker on my passenger side mirror that says: "objects in the mirror may appear closer than they really are" except in reverse, the objects in the 8x32 LX are farther apart than they appear.

Somehow my brain or the mini-me brain in my eye (thanks for that info, Ed) takes these cues and interprets them as the LX having significantly less DOF than the SE.

But wait, there's more. The compressed view and fast focuser played havoc with my focus accommodation. At different distances I had to reset the right diopter like I do on most 10x bins. And what is the difference btwn 8x and 10x bins besides the magnification? Tens have less DOF. Bingo. My brain "reads" the 8x32 LX image as if it were a 10x bin.

If the views weren't so damn gorgeous, I would have flipped it in 60 seconds since it required way too much work as a trade off for the conveniences of using a midsized bin, and at 25.4 oz, lighter weight wasn't one of those conveniences.

From what I've read, my expectations are that the 8x32 EDG would obviate the issues I had with the 8x32 LX including a bit too much CA and difficulty handling. But my expectations have been wrong before...

Brock
 
Hello Ed,

Not being one to take your ideas lightly, I gave more thought to a way to either verify, or change, my thinking.

I came up with the idea of throwing together a simple focus distance collimating lens (being way to lazy to go outside and do all the measuring required) and used a fork with 6 mm spaced tines, turned at an angle to bring the distance to about 5.5 diopters between them. I wanted to keep the spacing larger than the DOF of the bino used, a 7x50 Pentax to make out of focus obvious. With one end tine focused at infinity that made the other tines approximately 8.9 m, 4.6 m and 3 m distances using the lens law. I checked this with the calibration scale left on from a recent review of the bino.

The setup was the fork at the focus of a 50 mm, f:/4 lens, the bino under test and then a frosted glass projection screen in exit beam. This takes the eyes and camera out of the equation. There is only one tube being used, so no stereopsis, and since the image is projected to a flat glass, there should be no visual cues with a distance difference on the back side of the glass, just a flat image. See first picture attachéd, pardon the mess, I worked on a new setup all weekend and piled a lot of stuff on that table and have not finished and got around to putting it up yet.

It took a lot of light to project back to the screen, but believe me, I checked by focusing on each element individually and looked at the out of focus tines. There was great detail in focus because of the large apparent angle at infinity focus which does not show up in the projected image, but the out of focus blurring is consistent. The last picture was focused at about 6 m, about half way between the middle tines (approximately).

Since there is no brain, CCD, stereo effect or 3D artifacts to be processed on the back side of the screen, I have to conclude, at least to myself, that the DOF blurring is coming from the binocular. I feel somewhat more comfortable with my earlier posts now.

Best

Hi Ron,

Sorry, I don't understand this. What is a "focus distance collimating lens"? You refer next to the DOF of the 7x50 binocular, which theory says it doesn't have (at least at zero diopters). So how do you know what it is? My confusion gets worse after this, so no point saying more without clarification. :stuck:

Ed

PS. Let me add to that. If you believe that binoculars do have a finite focus and DOF (at zero diopters), please explain how this squares with the definition of an afocal system and the basic lens equations. I'd really prefer to be corrected than continue in ignorance. Seriously.
http://en.wikipedia.org/wiki/Afocal_system

e
 
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I think you are on to something here. I think a lot of us see what we want to see. I also am coming to some realization, as I look further that maybe the differences in percieved depth are not as great as they seem if I try to measure them. However, they still look to be there. So I think "percieved" is key, and may be one reason why one binocular is ultimately preferred by one particular user over some others.

I will add something here. I recently got a new Kruger Caldera 8x42. I ordered this one from a dealer. I originally looked at this glass in the Kruger factory which is about a two hour drive north of where I live. I was quite impressed with the one I looked at in the Kruger facility. I was less than impressed with the one I ordered. The two binoculars would have yielded the exact same images as posted by Norm Jackson of the chess pieces. The one I ordered was the second image, the one at Kruger the first. You would never have guessed they were the same model binocular. I wound up back at Kruger with this binocular. It turns out the one I ordered had some issues. One barrel was about 2.0 arc seconds less resolution than the other barrel. The collimation, while nearly within specs, was not real good. I was with the Kruger engineer when he checked this glass out, a pretty interesting experience. This should not have made it through QC, but did (or maybe had some shipping damage). With the binocular I ordered, looking at a tree full of Yellow Headed Blackbirds, you could get any one in perfect focus, but never two. There was no depth of field or focus, however you choose to look at the definition. So I am now wondering if some perceived depth issues may be telling us we have a binocular that is somewhat on the less than spec end of the acceptable spectrum of tolerances.

Issues aside, the Caldera is a very good binocular BTW.

Steve:

Interesting your post here, but it seems it has not much to do with the
topic of DOF of the 8x32 optics.

I suppose you could start this out as a new thread, about your experience
with the Kruger Caldera, and how you like them. :t: Issues aside.

Jerry
 
Here's another example of a midsized roof with a fast focuser that gives some users the perception of shallow depth of field...

Here's Kentucky Bob's take on the Minox 8x33 HG (which, btw, he likes if you read the entire post, I'll post the link to the thread below so you can read his comments in context):

"First the Minox HG 8x33 BR. True, if there is one criticism that is aimed at this binocular, it is from those who find the quick focus and narrow depth of field too difficult to reach sharp focus. If you want slow focus with precision--this is not the model to buy. The time and place for quick focus is hunting and other on-the-go applications where you do want quick focus."

His reply was in response to BinoBoy's post:

"The Minox have good optics but the focus is too fast for my tastes. The HG line goes from close focus to infinity in one turn. I find it takes a very delicate touch to get sharp focus. The IPD is very sensitive too. Using them is a lot of work. They've gotten good reviews from other members, though, so I guess it's a matter of personal taste."

Here's the thread:

http://www.birdforum.net/showthread.php?t=165887

But they are sure are cute...
 

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Steve:

Interesting your post here, but it seems it has not much to do with the
topic of DOF of the 8x32 optics.

I suppose you could start this out as a new thread, about your experience
with the Kruger Caldera, and how you like them. :t: Issues aside.

Jerry
The post was intended as a query about possible near defectsthat may or may not be present that may effect the percieved dof. That the example I used was a larger glass seems beside the point. I will post a Caldera review.

Brock

It has been said that you should be careful believing what you think. Maybe we should be a little more careful in believing what we see. As far as believing is seeing, I would submit that there is a powerful placebo effect that may well let people think they are seeing what they want to see, or perhaps to see what they think they should see. "This is a very expensive glass and I bet it will be really good"...and it is. Or maybe "this is just going to be a piece of junk"...and it is.
 
please explain how this squares with the definition of an afocal system and the basic lens equations. I'd really prefer to be corrected than continue in ignorance. Seriously.
http://en.wikipedia.org/wiki/Afocal_system

e

Hi Ed,

It will take me awhile to make a sketch or two for the rest, but the link you show is to what I term Teleconverters in cameras and beam expanders in other fields (laser, for instance).

A beam expander takes only collimated light input and multiplies its diameter by its focal length ratio factor and reduces the divergence by the same amount. One of my beam expanders (pictured) is a 3x, I put a 1 to 10 mm beam into it and get a 3 to 30 mm beam out, with one third the divergence. Useful for improving collimation and spreading light over a sensor to keep from saturating portions of the sensor while not getting any light to other portions.

The teleconverters, again, only take collimated light in and output collimated light, their purpose is to extend focal length by their factor, usually 1.7x or 2x while maintaining the lens aperture. There are ones that attach in front of the lens, do not remember what they are called, but the one for my old Nikon increases the focal length while maintaining the f#.

Neither of these devices are capable of being focused. The ring on my expander that looks like a focus control is actually an internal iris for cleaning up scatter.

Neither can be used with the eye very well, unless you have perfect vision. Focal systems (with focus controls) can match to eyes several diopters in either direction by changing the focus distance.

I will get back to you on the rest when I have time to put together some basic points.

Best.

PS: Since no focal plane (some, depends on type), these cannot form a real image, but pass virtual images.
 

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The post was intended as a query about possible near defectsthat may or may not be present that may effect the percieved dof. That the example I used was a larger glass seems beside the point. I will post a Caldera review.

Brock

It has been said that you should be careful believing what you think. Maybe we should be a little more careful in believing what we see. As far as believing is seeing, I would submit that there is a powerful placebo effect that may well let people think they are seeing what they want to see, or perhaps to see what they think they should see. "This is a very expensive glass and I bet it will be really good"...and it is. Or maybe "this is just going to be a piece of junk"...and it is.

Ron,

There is definitely a "group mind" at work. Otherwise, media ads would be ineffective in convincing people that their products are superior. Or as Mick put it many long years ago:

When I'm watchin' my TV
And that man comes on to tell me
How white my shirts can be
But he can't be a man 'cause he doesn't smoke
The same cigarettes as me....

Jack Trout, author of the popular marketing book "Positioning: The Battle for Your Mind" would also agree with you.

In it he says: The mind accepts only that which matches prior knowledge or experience.

What throws a rhesus monkey into his theory is that some people have more finely tuned BS detectors than others and not only can think "out of the box" but also see what the Madman marketing machine doesn't want them to see.

As I commented above, I wasn't expecting to see "rolling ball" in the full sized HG/HGLs, but I did, and the views were otherwise so good that I really didn't want to see and even used them every day for a month in hope that my brain would finally adjust to their curved world, but it didn't.

I think experience and age are also factors. You've heard the saying: You can't teach old dogs new tricks.

I think today in particular with the fast pace of change not just in technology but in all arenas of life, it makes people want to cling to old familiar ways. Put on the blinders and see what they want to see rather than what's actually before them.

Other people are simply too lazy to think for themselves and buy into the "party line" without question.

However, there are some of us, I call us the Toys 'R Us Kids ("I don't want to grow up, I'm a toys are us kid") who have retained that youthful malleability which enables us to see the world (and in this case, the world through binoculars) with "fresh eyes".

Not something I really cultivated, in fact, considering all the naysayers around me, my sensitivities can be as much a curse as a blessing.

If Kentucky Bob is reading this, I will let him speak for himself, but I don't think his perception of shallow depth of field in the Minox 8x33 HG is due to "group mind". I think it is what he actually sees, and in his case, he finds it an asset.

It's hard for me to imagine what it is like to be you, with your sharp, analytical mind and lab full of measuring devices, most of which I can't comprehend.

If I thought as you do and could see what is objectively there in bins through my measurements, I might experience a shift in perception to match the results of my research. Far better that than shifting perception to what the madman tell us.

Being mathematically challenged and naturally pig-headed, I sees what I sees and reports it as I sees it. If the experts and their lab devices say differently, that's fine and I accept those results, I'm not a Luddite, but those objective tests won't change my perceptions and neither will the madman's propaganda.

Brock
 
Hi Ed,

It will take me awhile to make a sketch or two for the rest, but the link you show is to what I term Teleconverters in cameras and beam expanders in other fields (laser, for instance).

A beam expander takes only collimated light input and multiplies its diameter by its focal length ratio factor and reduces the divergence by the same amount. One of my beam expanders (pictured) is a 3x, I put a 1 to 10 mm beam into it and get a 3 to 30 mm beam out, with one third the divergence. Useful for improving collimation and spreading light over a sensor to keep from saturating portions of the sensor while not getting any light to other portions.

The teleconverters, again, only take collimated light in and output collimated light, their purpose is to extend focal length by their factor, usually 1.7x or 2x while maintaining the lens aperture. There are ones that attach in front of the lens, do not remember what they are called, but the one for my old Nikon increases the focal length while maintaining the f#.

Neither of these devices are capable of being focused. The ring on my expander that looks like a focus control is actually an internal iris for cleaning up scatter.

Neither can be used with the eye very well, unless you have perfect vision. Focal systems (with focus controls) can match to eyes several diopters in either direction by changing the focus distance.

I will get back to you on the rest when I have time to put together some basic points.

Best.

PS: Since no focal plane (some, depends on type), these cannot form a real image, but pass virtual images.

Ron,

I've quickly reviewed basic optical lab equipment and practices as described by my all-time hero, Warren J. Smith in Modern Optical Engineering. Not that I've ever used this stuff, but I now have a better understanding of what you said and probably where you're going. If you have a copy of the book that would be great.

Part of my concern is statements like "... but the link you show is to what I term Teleconverters in cameras and beam expanders in other fields (laser, for instance)." The link was to show the universal understanding that telescopes are afocal. Yes, other devices are also afocal, but I have the sense you are trying to refute this fact. Assuming that I misunderstand (i.e., you concur that telescopes are afocal), however, then it is still entirely possible that conclusions I have drawn about DOF and related properties are incorrect.

The basis for my conclusions is summarized in this attachment, which is copied from post #50, thread http://www.birdforum.net/showthread.php?t=81438&page=2. "The Bino's New Clothes" came from my personal epiphany at the time, that like the Emperor of old we all see what really isn't there. See the paragraph after eq. 8. (I guess this discussion is really a continuation of what we said four years ago.)

I didn't mention there that the same lens combination equations show that the focal length of the combined eye-telescope system is that of the eye itself. Very helpful. What happens when the telescope is not set to zero diopters for terrestrial viewing is more complicated. However, literature research seems to indicate that it can be understood mathematically by the introduction of two related concepts, effective magnification, and effective afocal telescope. Although encouraging, I didn't pursue it further because dynamic parameters within the eye guarantee lots of variation in moment-by-moment perception. The need for differential equations is almost inescapable.

Ed
 

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Hi Ed,

I am getting ready to hit the road right now and got some new equipment in the big brown truck today, so going to play with that awhile. I will read your links later tonight.

This is just a quick, off the cuff remark, and I may want to take it all back later. A thought that occurred to me, afocal is ok as long as everything is collimated (parallel rays), whether physical or optical. Parallel rays imply infinity focus and I agree that as long as objects are at infinity and the focus is at infinity, there is no DOF. The condition falls apart though when objects, or light, is closer or starts diverging. Once divergence is apparent then focus blurs and this is where DOF comes into play. Say for a 10x bino, all you look at is farther away than, say, 200 meters, then focus is irrelevant. Move that same object to 30 meters and you have to change something.

I have never seen a lens, of any type, that can focus all distances at the same time, if you have one of those I want one.

Got to run. Later.

Have a good day.
 
Here's another example of a midsized roof with a fast focuser that gives some users the perception of shallow depth of field...

Here's Kentucky Bob's take on the Minox 8x33 HG (which, btw, he likes if you read the entire post, I'll post the link to the thread below so you can read his comments in context):

"First the Minox HG 8x33 BR. True, if there is one criticism that is aimed at this binocular, it is from those who find the quick focus and narrow depth of field too difficult to reach sharp focus. If you want slow focus with precision--this is not the model to buy. The time and place for quick focus is hunting and other on-the-go applications where you do want quick focus."

His reply was in response to BinoBoy's post:

"The Minox have good optics but the focus is too fast for my tastes. The HG line goes from close focus to infinity in one turn. I find it takes a very delicate touch to get sharp focus. The IPD is very sensitive too. Using them is a lot of work. They've gotten good reviews from other members, though, so I guess it's a matter of personal taste."

Here's the thread:

http://www.birdforum.net/showthread.php?t=165887

But they are sure are cute...

I made a contribution in that thread. I liked the Minox in most ways but not really in the field - my Fury 6,5x32 outperformed it in speed of use.
The reasons are its much easier eye placement and greater eye relief, its clockwise focuser and way better DOF.

The Fury's focusing speed is very fast, but thanks to the enormous DOF I make very little back-and-forth movement. I found the Minox much harder to obtain perfect focus with, and I have described it as a zone of confusion.
(sharpness is so-so within a certain depth, and this makes the pinsharp focus hard to find)

My Monarch X 10,5x45 seems to have a similar eye relief as the Minox, but is easier to just grab and see with. Its focus is very speedy as well, but I would claim that the shallow DOF makes it much easier to find pinsharp focus, so there's surprisingly little back-and-forth turning with the knob.

Perhaps 8x is a very bad compromise for me... Consider getting a Fury 8x32 and let you know how it compares with the 6,5x. I assume it is the same objectives but other eyepieces.
 
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