Optical Performance (1 Viewer)

I am sure that, like some of you, I spend a good deal of time not only using binoculars but also thinking about them as well. One area that has plagued me for some time is the issue of a binoculars’ subjective optical performance. This may sound simple at first but it is not. It tends to fall into the range of discussion in perception but not entirely.

I have tried to put some type of terminology to what I am referring to but have had difficulty finding just the right terms. So, for lack of a better phrase let me clarify what I mean by “object performance, field performance and overall performance”.

Object performance refers to the binoculars’ visual presentation of a specific object. Simple right? So, if you are looking for a Snowy Owl in the middle of cornfield then the way the binocular represents the Snowy Owl to your eyes is the binoculars’ object performance. The distinction here is between object performance and the other two types. Object performance does not necessarily depend on issues such as the type of distortion surrounding the other edge of the field of view….assuming that the object fits snugly into the sweet spot of the binoculars’ image. It does depend on issues such as apparent sharpness, apparent contrast and color representation. A perfect example of this was noted in a discussion I had with another forum member a few weeks ago. He objected to the type of edge performance a particular model displayed when he was scanning the open sky looking for raptors. What he stated was “…it bothers me but when I find a bird and focus the binoculars on the bird then the edge performance issues disappear because all of my attention is focused on the bird itself (object).”

This is distinctly different from what I want to call “Field performance”. Field, in this case, is referring to the overall impression that the binoculars full field of view provides to the user. This is extremely dependent on the width of the binoculars apparent and true field of view. Case in point, I have really been dabbling with some of the older model 7x35 porros lately. Because of their use, many times, of both single coated lenses and possibly Bk-7 prism they do not excel in the optical performance areas that many of us take for granted these days. They are not as bright or as filled with contrast as modern roofs nor do they typically have the neutral color representation. Images appear slightly yellow in comparison.

These shortcomings do take away a bit from their “object performance” but their design does contribute greatly to very good “Field Performance”. Because their field of view is generally huge (10-12 degrees) and because they offer the porro 3D-effect the image is exceptionally relaxing and easy to use. They just have that natural “oh, here is what I typically see when I look at something without binoculars just much closer” feeling to them. I am guessing this correlates with a human’s normal width of focused, unaided attention.

Overall optical performance is a term I would use to describe binoculars which have great object performance but also provide better edge performance. Many of the Alpha binoculars would fall into this group. Models such as the Nikon SE, Premier LXL and EDG, the Swarovision, etc… The only issue these binoculars are lacking is in a true “ultra wide angle” field of view. To accomplish this, in my opinion, their fields of view would have to approach or exceed 70 degrees.

Now, you are probably wondering why I am taking the time to relate any of this. Well, the answer is not too complicated. As I mentioned I have been having a hard time putting some of my experiences into words. There have been several binoculars whose levels in “object performance” areas have been first rate….on par with binoculars costing quite a bit more. Other models I have been trying offer an equally satisfying viewing experience but lack in certain object performance areas.

I guess what I am trying to say is that different binoculars can please us for different reasons. Depending on what type of activity you intend to use them for you may find one type of performance equally appealing to another.
Just something to think about.

For me, there is only one primary need for a bin. to deliver to be worthy, they must give outstanding views of birds.

I may spend the better part of a day in the field looking at rocks and roofs for CA, or reading signs and testing the size of the sweet spot or edge performance, or trying to invoke glare or flare from some absurdly backlit situation.

There are times, during these ''inspections'', that I may find some apsects of the bin lacking. Then, I start looking at birds again and [in the case of my FL] they just look gorgeous, perfect, accurate. You can push a bin to perform in many non real world situations, while ignoring the simple fact that these are birding glasses and they must perform [for me] as such.

That's why I still sing the praises of my FL, as [sure] it doesn't have the edges of the EDG or SV, but the view of a bird is so pristine, so elegant and so satisfying, I do not feel the need to look for something else.

James,

Thank you for sharing your experiences. That is exactly what I was referring to. Different folks look for different optical performance areas in their binoculars. No one binoculars is going to please everyone as we each tend to put emphasis on different issues.

I was just looking to put terminology to some very specific subjective experiences.

Interesting Frank. I pretty much pay attention to three things. What you call Object and Field performance, and eye comfort; meaning relaxed eye muscles when viewing for an extended period, without let up.

Jay,

I understand where you are coming from. As I made reference to in my comments surrounding field performance and the older style porros, I just thoroughly enjoy putting them up to my eyes. Yes, the image goes soft in some models after 50% but it doesn't take away from the pleasurable viewing experience provided by the other optical areas.

On the other hand there are many binoculars that provide a wonderful object performance experience and good overall experience but lack in the field of view area.

I'd like to once again promote the PFOV concept as a part of your "field performance". While a binocular's AFOV may be modest, it may still provide a great sense of transparency. This is presumably achieved by big ocular lenses, collapsed eyecups and sleek design. The thinner the black circle around the image, the more of the out-of-image FOV will be perceived. This does not fully make up for a smallish AFOV, but it enhances the viewing pleasure and the ease of view.

I think I am following you but not quite. So you are basically saying that a binocular with a larger PFOV (perceived field of view?) but a smaller apparent field of view provides a sense of transparency via larger oculars? The collapsed eyecup part has me a little confused. The setting for the eyecups varies from person to person. Some folks cannot collapse the eyecups completely because it provides too much eye relief which leads to blackouts and/or a form of tunnelvision. The larger ocular part I understand as I often find myself leaning towards binoculars that do have larger oculars for a variety of reasons.

Do have a particular model(s) in mind so thought I can relate to what you are describing?

FrankD said:

I think I am following you but not quite. So you are basically saying that a binocular with a larger PFOV (perceived field of view?) but a smaller apparent field of view provides a sense of transparency via larger oculars? The collapsed eyecup part has me a little confused. The setting for the eyecups varies from person to person. Some folks cannot collapse the eyecups completely because it provides too much eye relief which leads to blackouts and/or a form of tunnelvision. The larger ocular part I understand as I often find myself leaning towards binoculars that do have larger oculars for a variety of reasons.

Do have a particular model(s) in mind so thought I can relate to what you are describing?

Click to expand...

An older thread where I have discussed this:
http://www.birdforum.net/showthread.php?p=1892964#post1892964

See attached image in post #5.
My understanding of these things may be slightly different than then, but the discussion is still valid, IMO.
Today, when I also own the Zeiss FL 10x32 with its enormous 69 degrees AFOV, I notice a marked difference when I switch between it and the Fury 6.5x32, but since I use the Fury exclusively with spectacles and the eyecups down, the PFOV still feels great.

However, my new spectacles rest closer to my eyes and I need to raise the eyecups a couple of millimeters. Then, the increasing width of the black rim is immediately notable.

Another bin that has been praised for its great transparency is the Meopta Meostar 8x32. Its barrels are sleek and don't obscure the FOV as much as the fattier models. And I guess even the Swaro EL 32s are made in a similar shape.

Frank,

Those are some useful layman's terms for categories of visual experience. Each of those terms, however, has a significant semantic "field" (i.e. breadth of meaning), and are subject to a lot of slippage and interpretation; but I think they are useful nonetheless if folks don't take them too technically and simply use them to represent visual priorities served by a given device. To these terms I might add practical performance as a general term encompassing ergonomics, ER, cold weather and wet weather performance.

In my case, 8x30 EIIs give me very pleasing object and field performance, but represent significant compromises in practical performance.

Thanks for the good thread starter!

David

Frank,

Thanks for starting this thread. :t:

I don't have time to participate right now, but if it's still going in a week or so I'll be there.

In brief, I think you hit the nail on the head. Everyone talks about the binoculars and almost no one talks about the view seen through the binoculars. "The view," of course, is the psychological reality not the physical one, the same elusive thing that Steve Ingraham struggled to illuminate in (many of) his BVD articles.

Keep it going.

Ed

Frank,

After reading countless postings on various forums, I agree (with elkcub) that you hit the nail on the head.

I think it’s best if writers with experience of several good binoculars tell the forum which are their favourites considering only those three variables/parameters/criteria and nothing else.

Frank, may I ask, what’s yours?! I don’t think my own experience is wide enough to volunteer, but please see below.

May I suggest that they do that and then if they wish comment on other variables.

One I have noted, or imagine Ihave noted, is “teleporting”, for want of a better word, which I have felt with Nikons. By this I mean that typically other makes of binocular “bring it to you” while Nikons “take you there”!

My main, and pretty much only, binocular is a Leica Ultravid 10x25, chosen over the corresponding Nikon for its smaller bulk and weight, after using Nikons for decades.

Because of an obsession with smallness, I have sacrificed “field” for the other two parameters.

Frank,

I was wondering when you would get around to posting this. As I mentioned before, this paradigm really helped me clarify and sort out what I was looking for in a binocular. It's nice to have the terminology to sort out and organize your experiences in such a way that you could then stand back and look at it and get a clearer idea of what your after. David's idea of practical performance is another one I find very useful also. I''ll have to say, that at the time that I was experiencing the dissatisfaction with the hazy donut on the edges at the hawkwatch, I was not even aware of edge sharpness, field curvature, pincushion or what have you. I just knew it was taking away from my overall experience of the day. I rather enjoy the spectacular views from the hawkwatch and part of the enjoyment is enjoying those views through a nice pair of binoculars while scanning for birds. True the objective experience of those binoculars were spectacular when I got on a bird, but I want the whole enchilada. By the way, that requirement in a binocular is only needed for me when I intend to use it on the hawkwatch. Otherwise edges don't matter to me. Of course I give up some field of view, which is a compromise, but I enjoy the overall experience more. I believe I am experiencing something similiar to what looksharp is suggesting also. I wear contacts when using binoculars and find with the eyecups fully extended I get a tunnel vision, like I'm very aware of the circular outline of the binocular view. Yet when I turn the eyecups down as far as I can without getting blackouts and I rest the eyecups on my eyebrows and tilt the bino up slightly, I get a more expansive field of view. Almost as if my awareness of the circular outline all but dissappears. I prefer this viewing technique and feel it gives me a better field performance on all of the binos I've used, with the exception of my se's, because of the non adjustable eyecups. (practical performance) I also find that practical performance could definitely have an effect on objective performance. If I am having trouble holding a peticular binocular steady because it's not comfortable in my hands, or too light or too heavy etc. it definitely has a detriemental effect on my objective experience. Anyway, nice thread Frank, I like it.

John

LS,

I didn't go back and read the thread you linked to but will do so shortly. However, judging by what you posted I think I know what you are referring to. Tunnel vision/eye relief issues sounds like it makes the most sense. Some binoculars don't have enough eye relief for some users so they end up with tunnel vision...even with the eyecups fully collapsed. In order to see the full field of view and actually experience all a binocular has to offer there needs to be enough eye relief for you to be able to see the field stop (the edge of the image where it goes from what you are viewing to the "black circle" that surrounds it).

The interesting part that you brought up is the Meopta Meostar and and issue that I personally run into with eye relief and binoculars. I don't wear glasses but I do require binoculars that have a larger than average amount of eye relief because of the shape of my face. I have a high and wide bridged nose plus my eyes are set relatively close together. Full-sized binoculars with average sized eyepiece/eyecup diameters don't pose a problem for me as long as eye relief is in the 16-17 mm range or greater. If the binoculars' eyecups are wider then I need more eye relief to be able to see the full field of view and avoid tunnel vision. Some binoculars, like the Meopta Meostar 8x32, have narrower eyecup diameters so the eyecups actually fit past my nose and into my eye sockets. This happens often for me with smaller objective models (28 mm and under) so even if they have short eye relief I can still see the full field of view because the eyecups fit past my nose and closer to me eyes.

David,

I understand what you are saying and agree with you. Those are the best terms that I could come up with...at least for the moment...to attempt to describe what I was referring to in a useful manner. If anyone else has suggestions as to different layman's terms to describe each of those experiences then please suggest it. I am sure someone could come up with some just as descriptive but more specific to each of these experiences.

I do like, and agree with, your suggestion of practical performance. I had wrestled with suggesting something along those lines as well but just couldn't come up with something that specifically described what I wanted it to. Practical performance sounds great as it does factor in such issues as eye relief, focusing speed and tension, etc... These are mechanical/design issues but they do play a part in a binoculars optical performance for many users.

Ed,

I was hoping you would chime in because, as I referenced in my original post, this topic is as much about perception as it is physical reality. Recognizing that one enjoys a binoculars view is one thing but being able to sit back and describe why they enjoy the view in reference to other models with different performance parameters is the tricky part.

I look forward to seeing your input on this when you have the chance.

Pomp,

That is a tough and easy question to answer. I said it is "tough" simply because my list of "favorites" is constantly evolving as I true new (or old) models with different designs.

If I take those 3 (now four if we consider the suggestion of Practical performance) criteria and apply it to some of the models I currently enjoy using then it may be useful.

My fascination over the last month or so has been on ultrawide angle 7x porros...typically 7x35 but also some 7x50. I will take one of them, a recently arrived Sears Discoverer 7x35 and apply it to the "equation".

Object Performance:

Good apparent sharpness and low levels of CA. Average brightness (compared to today's roofs and porros with modern coatings) and contrast.

Field Performance:

Excellent overall because of the huge 11 degree field of view. The sweet spot is only about 50-60% of the field but because the field of view is so huge you don't pick up on it in casual use. Magnification also plays a role in this since this a lower powered binocular. As a result the depth of field is very good so a great deal of the objects in the sweet spot are in focus and free of observable distortion. Great 3D effect because of the porro design.

Overall Performance:

This is one that does not excel in this area because it sacrifices edge performance in preference for the extremely wide field of view. I would say this is this binoculars design's weakest area. It does appear as if you are taking an unaided image and just making it larger because of the high scores in the three field performance areas but upon careful inspection (allowing your eye roam around the image) you do pick up on the edge performance issues.

Practical Performance:

Based on the criteria that David listed I would have to rate this model as average to below average for a few key reasons. For one it is not waterproof. Two, it is a classic porro which means that the focus stiffens in colder weather. I don't find eye relief an issue for me personally. See what I mentioned above to Looksharp. In the case of many of these classic porros you can remove the metal eycups which allows me to narrow the interpupilary distance thus giving me the advantage of the full field of view. In other words I can see the field stops despite the huge field of view. Ergonomically I enjoy the binocular as the shape of the dogleg prism housing fits my large hands very well.

To offer a counterpoint comparison I would offer up the Zeiss FL 7x42...probably my favorite current "alpha" for a variety of reasons....

Object Performance:

Very good for a variety of reasons. The image is sharp in the sweet spot with literally no observable CA. The image is also extremely bright with a neutral color representation. Everything I put into the center of the field of view is beautiful to look at.

Field Performance:

Very good for a modern roof since it sports a very large 450 foot field of view plus the apparent field of view for a 7x roof is 60+ degrees. The largest I have found for any contemporary 7x roof design. The excellent depth of field because of the 7x magnification also factors into its excellent performance in this area.

Overall Performance:

This is a tough one to classify with this model. The astigmatism in the outer 1/3rd of the image definitely impacts its performance in this area. It is the one area that it is deficient in in my opinion. Because of that I don't think I can rate this model and configuration as anything but average at best in this area.

Practical Performance:

I think it performs very highly in this area. The ergonomics are not ideal but are very good for my hands. I have had no problems with the focusing speed or tension. It is waterproof and is not greatly affected by cold weather. Eye relief is good for all users.

John,

Sorry it took so long for me to getting around to posting it. There was a great deal I wanted to try to relate/describe and it took a bit of time for me to be able to put into words on the screen. Glad it helped you out with your binocular choices.

Hopefully see you soon.

FrankD said:

On the other hand there are many binoculars that provide a wonderful object performance experience and good overall experience but lack in the field of view area.

Click to expand...

Hello Frank,

Very welcome thread Frank. Thanks.

Let me make some comments:

I wonder if I need your concept of 'overall field performance'. It seems to me that 'overall' is just 'object performance' plus 'field performance'. Your examples proof the point (why mention apparent or real FoV under 'overall performance' as it can be categorized under 'field performance' with no problem at all?).

The nice thing about your contribution is that it deals with subjective evaluation and the concepts used in this. However, I think it's important to keep aiming for objectivity to the best of our ability. For instance, we definitely need to specify our reference(s) when evaluating optics. It's completely without meaning to say for instance that FoV is disappointing if we don't mention against what we're comparing. That is, we will get lost in subjectivity.

Having said this, have a look at the quote please. You mention FoV here, which as you've said in your original post is an aspect of field performance, so I'll rephrase it somewhat and we get this: 'On the other hand there are many binoculars that provide a wonderful object performance and good overall performance but lack in field performance'. Now does this still make sense? No to me it does.

More later I guess.


Renze

Frank,

First, thank you very much for the so prompt and detailed reply to my query which is really useful to me.

I would like to write at greater length than this, but various commitments keep me from it, including a thread I started today (in which I am happy to see you’re a contributor) that demands a lot of attention (something you of all people must be quite familiar with!) For now:

1. I think the criteria should be kept to the original three to be effective. More on this when...

2. It seems to me that a major factor in your “field” parameter you have not mentioned is the exit pupil.

3. From point ‘2’: why else, I wonder, would you rate the Zeiss Victory 7x42 over the 8x32, which has a bigger apparent (or perceived) FOV and better edge performance. (I know about these bins only by reading about them.)

Renze de Vries said:

Hello Frank,

Very welcome thread Frank. Thanks.

Let me make some comments:

I wonder if I need your concept of 'overall field performance'. It seems to me that 'overall' is just 'object performance' plus 'field performance'. Your examples proof the point (why mention apparent or real FoV under 'overall performance' as it can be categorized under 'field performance' with no problem at all?).

The nice thing about your contribution is that it deals with subjective evaluation and the concepts used in this. However, I think it's important to keep aiming for objectivity to the best of our ability. For instance, we definitely need to specify our reference(s) when evaluating optics. It's completely without meaning to say for instance that FoV is disappointing if we don't mention against what we're comparing. That is, we will get lost in subjectivity.

Having said this, have a look at the quote please. You mention FoV here, which as you've said in your original post is an aspect of field performance, so I'll rephrase it somewhat and we get this: 'On the other hand there are many binoculars that provide a wonderful object performance and good overall performance but lack in field performance'. Now does this still make sense? No to me it does.

More later I guess.


Renze

Click to expand...

Renze,

What I was referring to in that sentence you quoted was a way of classifying some of the alpha class binoculars. They have very good object performance and their edges are good (overall performance). What some of them lack though is field of view potential. Many folks think a 60-65 degree apparent field of view is good but, as you mentioned, in comparison to what? Other modern roofs? Yes, it is in that case but what about in comparison to other binocular designs that have been on the market for 50 or 60 years? If we could design large ocular/wide field eyepieces at that time then what is stopping us now? Prism size and the limitations of the roof design? That is what I was lead to believe from what I have read on the subject so far.

To clarify what "overall performance" is....Overall performance is a combination of good subject performance but good edge performance as well. You can call that a large sweet spot or sharp edges. Whatever you prefer. It also includes other factors that I probably just cannot think of at the moment.

Pomp,

I am glad to see your contributions on the forum. I forgot to mention that in your other thread.

To answer 2 and 3, yes, I am sure exit pupil plays a role but in the case of the 7x42 and 8x32 comparison I think you also need to consider the greater depth of field that the 7x provides in addition to the larger true field of view. In my somewhat comparative example earlier I simply chose the 7x42 FL because it was a current Alpha 7x to use versus the 7x35 Sears porro.

Frank,

I share your concern with FoV in todays binoculars. It seems the concept of ‘wide angle’ is something of the past, a lost art, or maybe I’d rather say a lost concern. At some point in time manufacturers seem to have agreed on 60 deg. AFoV as sufficient for a satisfying view. The great majority of efforts to make us happy have since been in accord with this (debatable) standard.
I think that if we want something more from our manufacturers we have to express our dissatisfaction, criticize the wide angle standard, redefine the norm.

However I feel that this is something quite different from what you’re up to in this thread, if I’m not mistaken: clarification, sharpening up the concepts used by us to describe the visual experience as clear, as specific, as useful as possible. Great. Because it can be a mess. Take sharpness for instance: it’s often completely obscure whether people are referring to sharpness across the field of view or to center field resolution.
Again, I’m happy with your concepts Object performance and Field performance. I’m happy as well with David’s addition of Practical performance. But as I like to see the concepts as discrete as possible, I can’t see anything being gained in the concept of Overall performance. My impression is that Overall performance will be the place where the reviewer summarizes his findings, discloses his thoughts on how certain factors are balanced and – probably – will tell us whether or not he likes the instrument. In this way I think the concept of Overall performance will be used for generalization and subjective opinion, more than for specific observation. Now I’m very well aware of the inevitability of all this, but my point is that we shouldn’t regard the concepts of Object performance, Field performance and Practical performance as being on the same level as Overall performance. And because of this, I say: let’s drop the Overall performance concept. Really, no harm is done. Let’s call it Summary and everything’s fine.

Renze

I've tried to outline a vocabulary, making use of Frank's and David's concepts.

Object Performance

Sharpness (retrieval of fine detail, resolution)
Contrast
Color representation
Immediacy


Field Performance

Brightness
Transparency
Sweet spot
True field of view
Apparent field of view
Depth of field
3D-effect


Practical Performance

Balance
Focussing
Eye comfort
Weather performance


As this is off the cuff, please join in.


Renze

Renze,

I would agree that "Overall Performance" is the broadest and most subjective of the categories, as it offers the impression of averaging together the other categories. Unfortunately, this is how most reviewing is done, by tallying scores for individual areas into one aggregate score that can be compared to others in a given product category. All manner of products are reviewed this way, from binoculars to beer, and it is those final scores that sell products. All the more reason to resist an overall, "broad strokes" rating and insist on more accurate evaluations of specific criteria.

I really like your vocabulary; it articulates areas of evaluation that are often lumped together or confused.

Good discussion.

David

Renze de Vries said:

I've tried to outline a vocabulary, making use of Frank's and David's concepts.

Object Performance

Sharpness (retrieval of fine detail, resolution)
Contrast
Color representation
Immediacy


Field Performance

Brightness
Transparency
Sweet spot
True field of view
Apparent field of view
Depth of field
3D-effect


Practical Performance

Balance
Focussing
Eye comfort
Weather performance


As this is off the cuff, please join in.


Renze

Click to expand...

This is a good concept for a thread Frank, thanks.

Now I really like Renze's post. I agree with his summation. I would add an argument here that the fourth category Frank used should still apply here. Overall Performance is, in my mind anyway, the way the other three performance levels add up to the sum of the total package. It seems to me Overall Performance is the seat of the stool supported by the three legs as described by Renze. Mess with any one of the three legs and you fall off the stool. Keep them in balance and it can be a comfortable place to sit.

This reminded me of a post not too long ago by elkcub. I forget the thread, but he used the term "presence". He used it in a psychological sense and talked about the use of presence in design of such things as Heads Up Displays in some military vehicles, for example. They had to be big enough to have the presence to be seen, but not so big as to have their presence overwhelm the viewer. Anyway maybe I have that a little incorrect . But is seems that each binocular design projects a presence. That presence I think may well be the deciding factor in either "I like this one" or "I don't like this one". This thread seems a good place to sort this kind of stuff out.