Experiencing image size in scopes and binoculars (1 Viewer)

[Renze de Vries]

Hello birders,

I'm rather new to this forum and so I don't know if this item has been discussed before, for instance in the scope-section. Anyway, I feel it belongs here. The problem is: I don't like scopes. I also know why: I'm addicted to binoculars, I don't like to look with one eye, and most importantly, I find the view through scopes very disappointing. Even the best telescopes don't come close to what I see (and feel) through my binoculars. Problem? Yes, for a whole bunch of people seem to like their scopes very much. They feel close to the bird, feel they can almost touch them, they love the view. This is what I hear and read all the time: scopes are tops. As I usually don't like to feel things alone, the first question is: are there maybe more people like me?
For the second question, let me explain a little better why I don't like the view through a scope. Yes. it's disappointing. Most and for all because the image feels small to me, at least smaller than what I see, feel, experience through binoculars. And that's strange. Because through a telescope the bird should be 30x or more larger, it is filling the whole field of view isn't it? Well, my experience is quite the opposite. Question: how to explain this?

Renze de Vries

 

[ranburr]

Renze, you are not alone. I have a rough time with scopes myself. I can always see better with two eyes vs one. I wish someone would develop a high quality 35 or 40x80, center focus bino. I would love to see someone like Minox do this.

ranburr

 

[elkcub]

Renze,

Your question really gives me a kick, or I should say your questions, since there are several mixed together it seems to me. I don't believe they've been discussed comprehensively, but they are certainly discussion-worthy. I'll just make a few observations of my own and run for the hills:

1. Being two-eyed beings our brains are wired to create an internal "spatial field" that allows us to operate in a three-dimensional world. This remarkable biological capability is so unconscious that we take it for granted. However, when normal visual cues are denied, enhanced, or distorted, the effects become conscious — and along with that come feelings and judgments (and optinions).

2. It is a rare person who prefers a monocular view to a binocular one. No doubt this is because the binocular view is closer to normal, where at low magnifications it is still possible to perceive a "spatial field," depending in part on the depth of focus, field of view, and binocular disparity afforded by the optics. The brain also adds it's own interactive dynamics which we refer to as "attention." I've proposed in other threads (now lost), therefore, that properties of the spatial field are not exactly the same as what can be surmised from the optics. In particular the sense of spatial extent and depth, as well as the ability to switch attention from object to object, are primarily properties of one's internal perceptual field.

3. The hyperstereo property of porro prism binoculars compensates, to some extent, for the raw effect of magnification. If the images are presented with normal retinal disparity (roof binoculars), objects are interpreted as being much larger and closer, within a relatively flat spatial field. Hyperstereo images (porro prism binoculars) add compensating distance cues (retinal disparity). The perceptual mechanism of size constancy is then able to produce a more "natural" percept, with less apparent magnification and closeness, and greater spatial depth. When it comes to perceptual tradeoffs, many birders favor the more natural percepts produced by porros. Some, like yourself, apparently prefer the "right there" magnification effect. I like each at different times, and a broad spatial field can give me quite a "wow."

4. Now consider telescopes that have no retinal disparity being monocular, huge magnification, narrow field of view, and shallow depth of focus. There are virtually no visual cues to construct a spatial field. The observer falls back on a flat image with minimum context and loses a sense of even how far away the subject is. Hence, in my opinion, it is not meaningful to talk about perceived size in the same way, or judge the "view" in the same terms. Telescopes are the domain of rendering detail in spite of the distance. Packing a telescope and tripod is the price one pays to get it.

Thanks for opening up this interesting subject. I hope there are more opinions expressed.

Elkcub

 

[elkcub]

... and furthermore, with regard to the apparent size of images viewed by telescope, try this experiment:

Get a roll of paper towels.
Using one eye, view an object (like pottery), about 20-30 ft. away through the center tube.
Now move the roll aside and view the object, again with the same eye.
Go back and forth. The apparent size should change quite dramatically, although the retinal projection (of the pot) is the same in each case.

Do you see how it appears smaller in the tube and larger with the full field? That's because there are distance cues in the full field (even monocularly) as well as other objects of known size. Hence the size constancy mechanism can work better with a full field than a restricted one. Similar principles apply to the telescopic view with the added complication of a magnified image.

-elk

 

[william j clive]

There is an instant cure for the problem of preferring two eyes. Buy yourself a small Mak, such as the Meade ETX90, then acquire a binoviewer and a pair of eyepieces. Hey presto, you have a two-eyed telescope, and it is brilliant!

I have a small mak I use mainly for astronomy, but I have used it occasionally for birding, at up to 150x, on days that have no shimmer. You can buy BC&F's Binomate now for around £170 in the UK, or the Burgess in the USA for $200 including a pair of free 20mm eyepieces.

The views of the moon using a Bino are quite amazing, much more of a 3D effect than observing with one eye, and detail seems to be much enhanced. There is also the advantage that you can observe longer and more comfortably with two eyes than you can in cyclops mode.

Problem solved!

 

[Renze de Vries]

I wish someone would develop a high quality 35 or 40x80

Thank you Rannburr for the moral support. But I doubt if large binoculars will solve our problem. I bought me a 20x60, admittedly of moderate quality, and learned it was absolutely useless for large distance viewing (and that's what you want to use it for, isn't it?). For large distances one needs all the light one can get, and my binoculars were simply incapable of transmitting enough of it. Then there's the exit pupil: I already felt uncomfortable with 3 mm, so I certainly wouldn't consider 2 mm. Maybe there are better solutions. Indeed, the binoviewer looks quite interesting, but there's very short supply of reports by birders. The other possibility could be image stabilized binoculars. Their magnification isn't quite on the scope level, but 15x or 18x Canons could bring the desired goal - get those damned sandpipers into view - a few steps closer. I certainly intend to try them out in the near future.

And Elkcub, many thanks. It's explained beautifully. I'm not so certain however of your proposition that birders who prefer telescopes over binoculars are rare. I know a lot of people carrying scopes and tripods but wearing binoculars of mediocre quality. In some cases I couldn't even imagine the owner could see anything through them.

Renze

 

[elkcub]

... I'm not so certain however of your proposition that birders who prefer telescopes over binoculars are rare. ...

Renze

Hmmm, I thought I wrote "... It is a rare person who prefers a monocular view to a binocular one." Well, based on William Clive's post, the generality may even extend to those who prefer the detail of telescopes to the spatial view of their low-power cousins. Using the traditional ploy "...but it's even more complicated than that," one notes that binocular viewing even gives rise to the impression of depth for the moon. I'm not a star gazer, but this must give pause for thought. Perhaps simply the use of two eyes in and of itself induces stereopsis? Since there are no retinal disparity cues (that the eyes could detect), it would appear the brain is free to create it's own world. Is it a case of mind over matter? :-O

PS. This may be a heretical question, but could it also be that biocular vision (same image to each eye) is superior to monocular vision (image to one eye only)? Superiority would be an improved ability to process information, rather than simply satisfaction at having both retinas stimulated.

-elk

 

[elkcub]

PPS. There are interesting writeups at the sites below concerning the superiority of binocular (or biocular) vision vs. monocular vision. Vision scientists seem to be agreed that through a process of "summation" the brain shows an improved ability to process visual information biocularly. In other words, more detail is seen even though identical information is presented to each eye.

In discussions with a friend who studies hyperstereo effects, rather curious 3-d illusions can sometimes be created when each eye is presented with the same image of a moving subject at different brightnesses. Apparently, one aspect of "summation" occurs at the retinal level, where it acts like a capacitor. Due to a time delay in transmitting the dimmer image to the brain, 3-d perceptions sometimes occur based on disparate (i.e., time delayed) retinal cues.

Not to take issue with anyone primarily interested in optics, it is clear that a full understanding of binoculars and telescopes needs to include how the brain processes visual information. Personally, I've become increasingly convinced that optical depth of focus and transmission efficiency have been unwittingly substituted for what are really complex perceptions of 3-space and image lightness.

http://www.foothill.net/~sayre/Why binoculars.htm
http://www.cloudynights.com/articles/binosvsscope.htm

Elkcub

 

[Tannin]

An interesting discussion, gentlemen. I'm going to have to go back and read it over more carefully before I can properly understand some of the concepts here. But first, before I get distracted by the remainder of the thread, an opposing view.

I am a scope man. I don't like binoculars, and when I do use them (rarely, for I am seldom without my scope, and tend to prefer the naked eye over bins even then) I usually close one eye. Why? I don't know. It just feels more comfortable, and I seem to be able to see more detail that way. Possibly this is partly because, looking at birds, you are always a little hurried - you want to get a good sight right away because - who knows? - the bird might fly off at any moment. So my natural urge is to keep things simple: just look through one half of the binoculars and close the other eye, rather than fiddle about adjusting them. But even with plenty of time, I prefer the one-eyed view. It has more presence, more apparent detail, more immediacy.

So I found reading your post very interesting, Renze. It's more or less the exact opposite of how I feel about optics - and one of the best ways to understand black is to spend some time studying white. (If you want to really understand how capitalism works, read Marx. If you want to understand the communist experiment, read some classical economics. And so on.)

Anyway, it was in that spirit that I started reading this thread. When I got to Elkcub's post, I tried a small experiment. Try it for yourself:

Look at an object in the room nearby, something of moderate size. (On the floor in front of me right now there happens to be a travel bag, a vacuum cleaner, and a large pile of books, each of them about 2 or 3 metres away. That's about the right size of object.) Study the object. Now, close one eye. Observe the differences. Open it again and observe again. Close the other eye and observe once more.

The views are quite different!

For me (and I'll be interested to see how different this is for other people) the one-eyed view is more immediate. The object stands out in sharper relief against the other objects in the room. It seems larger (though it isn't, of course), and there seems to be a sharper, more 3D distinction between the light and shade.

On the other hand with both eyes, though the object seems less prominent, I am much more aware of the general situation, of the other objects in the room, and of the room itself.

To try to explain by analogy, looking with two eyes is like being in a dark room and holding up a lantern - you can't see any single thing especially well, but you can see pretty much everything well enough. The one-eyed view, in contrast, is like shining a spotlight: you have an excellent view, but only of the thing you are pointing the spotlight at.

Elkcub writes "it is clear that a full understanding of binoculars and telescopes needs to include how the brain processes visual information." Absolutely!

With one eye, I find that I need to look more-or-less directly at the object of interest to see much detail, but with two eyes that effect is not so marked. Further, it is more difficultto pick out fine detail with two eyes - largely, I think, because it is much more difficult to concentrate properly on the object of interest.

PS: I have, so far as I know, fully normal vision; a fraction sharper than average for my age (45) but well within the normal range. But in any case, I don't think this is about eyes. It's as Elkcub says, about the brain and how it processes the signals our eyes produce.

 

[elkcub]

Tannin,

In looking over your posts on this thread and "Monocular Options?", the main difference seems to be your final choice of viewing instrument. I'm not sure you're all that "opposite," unless you have an underlying problem with binocular fusion. Going back to my post #3 (this thread), "... The brain also adds it's own interactive dynamics which we refer to as "attention." ... In particular the sense of spatial extent and depth, as well as the ability to switch attention from object to object, are primarily properties of one's internal perceptual field."

So my interpretation is that, barring a perceptual fusion problem, you simply choose to use one eye to eliminate aspects of the field that might otherwise distract your "attention." Since a telescope is almost useless for finding small objects, however, you prefer your unaided eyes for that purpose — which is okay within their limits of resolution.

So, let me ask you this. When scanning for things of interest with your unaided eyes, do you also close one of them? I'd be very surprised if you said yes. If you do not, why not?

The point I'm getting at is that in breaking with custom one can impose "higher order" preferential decisions based on private considerations. There is obviously no right or wrong to that, although it might come at the price of some inconvenience.

What did you think of the two articles I included in post #8?

Elkcub

 

[RAH]

You can buy large binocs, as mentioned above, that are 20x60, 30x80, etc. I do not agree that you don't get as much light thru them as with a scope. A large binoc like a 20x60 is just like putting 2 20x60 scopes together.

I think one problem is that folks seem to associate binocs with handholding, whereas with a scope everyone thinks of a tripod. With large binocs like a 20x60, you MUST use a tripod for long term viewing, just as with a scope. Of course, such an arrangement is much less streamlined than a scope.

 

[Renze de Vries]

Hello Tannin,

It gradually gets more complicated, and even more interesting. Yes, let's look at white for better understanding black. I'll make some comments.

1. I wonder if you are really, as Elkcub wants it, the exception to the rule. Maybe there are a lot more people out there who prefer the monocular over the two-eyed view. As I would like to hear of them, I posted a call for help in the telescope section (Happy cyclops, please join in).

2. Elkcub's argument for his statement that it is a rare person who prefers a monocular view to a binocular one (now I quoted you right, isn't it Elkcub?), is that the binocular view is closer to normal. At first sight this seems perfectly logical, but after your report of your favorite way of seeing I'm not so sure anymore. The problem is: what exactly is normal? As our perception is highly selective, i.e. equally capable of increasing as well as reducing information, the monocular view could be just as normal as the two-eyed one. Then there's the problem of the seeing aids themselves. I would say that the view our magnifying instruments (any instrument, be it binocular or monocular) present us with, is in no way normal. How hard we try (but we never do!), we will never see the bird 'as it is'. The bird we see through our binoculars and telescopes is not true to life (i.e. true to normality) but it is something else, something better, something brighter, something larger than life. I'm convinced that this is the reason why we enjoy our bins ands scopes: not because we can't see the birds otherwise, but because we are seeing them in an abnormal, more spectacular way.

3. What strikes me in your report, Tannin, is not so much the opposing view, as well as the rigorous way you stick to it. However, I do recognize some of the things you mention (more presence, more apparent detail, more immediacy, object standing out in sharper relief, spotlight), be it that I associate these more with the roof versus porro-view: because of the relatively flatter image of the porro-view, objects appear more acute. To me there's a strong analogy with high fidelity audio here. Or maybe I'd better not call it high fidelity but simply audio, as the fidelity to reality is to some listeners of no importance at all – they simply like to hear things as up-front and immediate as possible. And why not, as in most music there isn't even such a thing as 'reality' or 'the original sound'. Question is, do I care? Yes, I do. Because this wouldn't work for me. Because it doesn't suit my taste, my priorities, my values. And here we arrive at the real complexity of the issue at stake: I feel this isn't only about eyes, and about how the brain works, but also about who we are, how we want to experience the world. But maybe now the philosopher in me has taken over? Correct me if I'm wrong please.

4. Your experiment is amazing! It looks very much like a variation on Elkcubs tube, but the outcome is quite the opposite: the objects seem larger with one eye than with two. That is, through your eye(s). Not through mine. Really strange!

Renze

 

[elkcub]

...
2. Elkcub's argument for his statement that it is a rare person who prefers a monocular view to a binocular one (now I quoted you right, isn't it Elkcub?), is that the binocular view is closer to normal.
...
4. Your experiment is amazing! It looks very much like a variation on Elkcubs tube, but the outcome is quite the opposite: the objects seem larger with one eye than with two. That is, through your eye(s). Not through mine. Really strange!

Renze

#2. I guess so. I believe there is a species preference for binocular vision. My assertion was that a binocular view provides more visual information for the observer to build a 3-d percepual world, and that we're wired to do that. I'm willing to accept that only eccentrics navigate with one eye closed.

#4 Yes, that part has me puzzled too. Generally, closing one eye leads to a smaller image percept not a larger one. Having thought this to be universal, it led me to conclude that Tannin was really referring to his ability to focus "attention" on the object rather than its perceived size. Only he can say if that's correct. However, to quote his post #9: "...Further, it is more difficult to pick out fine detail with two eyes - largely, I think, because it is much more difficult to concentrate properly on the object of interest."

This also explains his stated ability to see more detail with one eye than two. Everyday experience and the references sited above suggest just the opposite for the population; however, that may be "average" findings and not indicative of each individual in the study samples. I was not intending to track down the data to find out, but average results can fool you sometimes. For example, there was a study done many years ago to determine the relationship between driving behavior and blood alcohol level. As expected, average driving performance got worse with increasing blood alcohol — BUT one or two individuals actually improved! (Nope, judges will not accept that argument.)

I think we share the analogy to high-fidelity music. To me, Porro = analog; Roof = digital. The former creates smooth auditory space, the latter crystal hard clarity. |=)|

Nice discussion guys.

Elkcub