The End All FL Edge Sharpness Thread (1 Viewer)

Pileatus said:

The market, i.e. sales, will provide the answer.

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Then why does only one binocular, the Swarovision market the sharp edge, much less achieve it? If that price tag is what it takes to get a truly sharp edge, then that may skew any sales figures.

That may well take awhile before the ability becomes more common in mid range binoculars, much like pentax finally phase correcting a good mid range binocular.

I tend to agree with Henry here too.

Alexis Powell said:

Sounds like you just need asymmetric eyecups. Maybe the winged type, with the wings shortened a bit and rotated to the top?

--AP

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Alexis, I just received winged eycups for my Swarovski 8x30 SLCneu today and this comes the closest to being what I have been searching for.

Sorry to be off topic some, I don't think the OP will complain much about it.

John Dracon said:

My comments probably have little relevance to this discussion, for I feel the commentators have superior knowledge of optics than I possess. I'm really a pragmatist , however. When I am using my eyes without binoculars. I see what is directly in front of me. Without moving my head or eyes, the further from the center of view the less is in focus. If there is something I want to look at on the edge, I move my eyes or head. I apply the same to binoculars. My subjective opinion is that high quality optics such as the older Zeiss models actually have better resolution in the center than the newest stuff. John

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John,

I just chanced upon this statement, which I meant to comment on earlier. Your observations, as well as others, are largely consistent with what we know about human oculomotor systems. The unaided eye has considerable rotation ability, but built-in biological mechanisms are designed to rotate the head and counter-rotate the eyes so as to center an object of interest. Prolonged viewing is almost always done near the median plane.

However, the unaided eyes also have considerable ability to see clearly in a wide range of asymmetric scanning positions, primarily to detect objects of interest, which can then be centered by the normal oculomotor mechanisms. Until recently, binoculars tended to limit that functionality (to see clearly at oblique orientations), which in my opinion is what has motivated optical designs to overcome this limitation. The metric is so-called 'edge sharpness,' although the relevant benefit is visual scanning.

It may or may not be true that scanning performance comes at the expense of center viewing performance. I'd like to hear more about the optical necessity of that. I do know that it comes at a dollar cost that I am currently unwilling to meet. So, at the moment I'm happy with what I've got until the industry catches up with my retirement income. Or, I fall off the edge.

Regards,
Ed

Ed,

Just briefly to the last point. Although it has been often stated that in order to have optimum off-axis performance, an optical design has to slightly compromise center viewing performance, I have never been able to see satisfactory empirical evidence of this. In all the binoculars I have tested, it has been overwhelmingly a matter of assembly/manufacturing "sample" defects if and when central resolution has been compromised, with meaningful contribution coming from scatter control (coatings/baffling influencing contrast). I have never been able to see a slightest hint of evidence that a field-flattener or an otherwise complex eyepiece construction would be detrimentally contributing to central resolution. The easiest way to see this has been using different eyepiece designs on the same spotting scope, where it has been very evident that the scope body (objective, possible focusing lens system and prism assembly) is always the factor limiting resolution. The only exception I could possibly think of would be scope planetary viewing with the highest magnifications possible for a given scope, where the very marginally better light trhoughput and lesser scatter of some of the very simple "planetary" eyepieces could give that last hair's breadth of advantage - providing the scope itself was truly diffraction-limited. With binoculars, the assertion that our design has soft edges because we want the center to be as good as possible is, in my opinion, only a marketing p.r. excuse.

Henry can probably chime in to prove me wrong if need be...

Kimmo

elkcub said:

John,

I just chanced upon this statement, which I meant to comment on earlier. Your observations, as well as others, are largely consistent with what we know about human oculomotor systems. The unaided eye has considerable rotation ability, but built-in biological mechanisms are designed to rotate the head and counter-rotate the eyes so as to center an object of interest. Prolonged viewing is almost always done near the median plane.

However, the unaided eyes also have considerable ability to see clearly in a wide range of asymmetric scanning positions, primarily to detect objects of interest, which can then be centered by the normal oculomotor mechanisms. Until recently, binoculars tended to limit that functionality (to see clearly at oblique orientations), which in my opinion is what has motivated optical designs to overcome this limitation. The metric is so-called 'edge sharpness,' although the relevant benefit is visual scanning.

It may or may not be true that scanning performance comes at the expense of center viewing performance. I'd like to hear more about the optical necessity of that. I do know that it comes at a dollar cost that I am currently unwilling to meet. So, at the moment I'm happy with what I've got until the industry catches up with my retirement income. Or, I fall off the edge.

Regards,
Ed

Click to expand...

Ed,
Thank you very much for this simple and all inclusive explanation! Your students must have voted you Educator of the Year at least once if we live in a just universe!

Your post alone makes this thread worth 5 stars!

Now if I can just find where to do that?

Good birding!

Bob

Kimmo,

My experience agrees with yours.

The only place I've found actual measurements of eyepiece resolution is the German website below. I've linked to a test of the Pentax XW 20mm which is a reasonable stand-in for a complex binocular eyepiece. It has 6 elements in 4 groups with an internal focal plane quite similar in layout to the SV eyepiece. It's center resolving power is about as good as any eyepiece in these tests no matter what their design and excellent (better than eyesight) resolution is maintained across a 70 degree field.

http://www.astro-okulare.de/English/pentax/penxw20e.htm

Ed,

I'm not sure just how expensive good off-axis corrections should be. The cost of the SV field flattener is imbedded in what would surely be a very expensive binocular even without it. The Canon 10x42 uses an even more complex eyepiece to achieve similar corrections and costs half as much as the Swaro. My Fujinon 8x30 FMTR-SX uses a field flattener for very good off-axis corrections and cost less than $400. These things have been around for decades in some binocular models from Fujinon, Nikon, Pentax and Canon. The European alpha brands have been curiously behind the curve.

Henry

So, to sum up this part of the discussion then, the FL’s “fuzzy edges” are not a “deliberate design feature” as some people (including myself) have assumed/asserted, but a simple fault. Is that a fair statement?

henry link said:

Kimmo,

My experience agrees with yours.

The only place I've found actual measurements of eyepiece resolution is the German website below. I've linked to a test of the Pentax XW 20mm which is a reasonable stand-in for a complex binocular eyepiece. It has 6 elements in 4 groups with an internal focal plane quite similar in layout to the SV eyepiece. It's center resolving power is about as good as any eyepiece in these tests no matter what their design and excellent (better than eyesight) resolution is maintained across a 70 degree field.

http://www.astro-okulare.de/English/pentax/penxw20e.htm

Ed,

I'm not sure just how expensive good off-axis corrections should be. The cost of the SV field flattener is imbedded in what would surely be a very expensive binocular even without it. The Canon 10x42 uses an even more complex eyepiece to achieve similar corrections and costs half as much as the Swaro. My Fujinon 8x30 FMTR-SX uses a field flattener for very good off-axis corrections and cost less than $400. These things have been around for decades in some binocular models from Fujinon, Nikon, Pentax and Canon. The European alpha brands have been curiously behind the curve.
Henry

Click to expand...

I would think this would be indicative of the very low level of 'need' or interest in this technology [for birders at least] up until now, it seems.

If birders had wanted flat fields and super sharp edges, they would not have kept buying multi-thousand dollar FL's, EL's and BR's. If the big brands figured they would make more money with models with edge-to-edge sharpness, I would think they would have built them years ago.

Have needs and desires of birders changed? I guess the SV will tell the tale....

fugl said:

So, to sum up this part of the discussion then, the FL’s “fuzzy edges” are not a “deliberate design feature” as some people (including myself) have assumed/asserted, but a simple fault. Is that a fair statement?

Click to expand...

My FL's have no more fuzzy edges than any EL, Ultravid, Elite I have tested. And ''fuzzy'' is an exaggeration, more recently used as a pejorative than a description of the model.

I was out with my 10's today.......fabulous view as ever, especially in the gloomy overcast, no fuzzy edges just a bit of fall-off towards the periphery...if you force your eyes out there. Really, now, how is this different from anything else out there? [without field flatteners]

I have let many of my birding friends use my bins.......all have commented on the brightness and clarity, none have mentioned edge sharpness, none read this forum either, I would think or they would have been all over it!

I’m not arguing a point just to argue, it’s just as clear as day that I don’t see what some others do, and it’s not for lack of trying or technical ineptitude. It’s as though you are telling me the FL’s are purple when, as I hold them in my hand, I can see they are black.


Here is some differing opinion,

Andy Bright said this, BF review

''I'm not going to bother with the meaningless optical performance of the peripheral edge of view, other than to say that the typical edge distortion isn't much different to any other bino and doesn't have any impact for the real world user.''

And later, added,

‘’Amazing that so few of the people with 'issues' against the FL haven't actually looked through one? Similarly curious that just two people who see a 'problem' have had such a huge impact on the threads against all those who have seen no problem AFTER using the bino.... another odd fact, probably of no relevance, is that of the geographical location of those with a concern.’’


24 Hour Campfire review, [Cornell]
‘’In terms of pure image quality, six models received “perfect scores” from our reviewers, indicating an absolutely flawless, bright, and crisp-from-edge-to-edge image. Of these, the Zeiss 8x42 FL T* scored the highest for overall quality of any binocular tested, combining its exquisite image with perfect eye relief, a relatively wide field of view, and excellent close focus. The similar Zeiss 10x42 was the only 10x model in our test to receive this highest image rating’’

Kimmo Absetz, Alula,‘’Image quality near the edge of field: It is generally easier to make higher magnification binoculars have better edge resolution, and this was also the case with the Zeisses. In our most recent test, the older 10x40 Victory had the best edge quality. The new 10x42 Victory FL is not quite as good, and fell a bit short of the Nikon SE. The sharp area in its image also does not extend as far out from the centre as in the Nikon. The 7x and 8x models are a little better than average for their magnifications. The Swarovski EL 8.5x42 has perhaps marginally better edge performance than the Zeiss 8x, although there were conflicting views about this among our team members. Pincushion distortion, which is almost always very prominent in binoculars, is exceptionally well corrected in the new FLs.’’

Funny, the EL’s seemed about the same at the edge as the FL’s. Why don’t we hear about this obvious defect when discussing the EL? Odd…….

He continued,

‘’Our favourite among the models was the Victory 8x42 FL, which our test team considered to be narrowly but unequivocally better than the number one of recent years, the Swarovski 8.5x42 EL.’’


TLB, Cloudy Nights
I've had a pair of the 7x42 FLs for almost a month. I am exceptionally pleased with them...enough so that I am seriously considering selling my Nikon 8x32 SEs.

The 7x42s do suffer from the edge sharpness issues attributed to the FL line but in practice the field of view is so large that I rarely notice it at all. In fact, the "field of apparent sharpness" (to make up a term) is larger than that of the 8x32 SEs.

What I mean is that, even though the SEs are sharper closer to the edge, the sharp portion of the 7x42s is larger than than that of the SEs even though they don't hold the sharpness as close to the edge. (Did that make any sense?)

Hinmark, Cloudy Nights
‘’the Zeiss 7x42 FL performs better than the Zeiss Classic 7x42 B/GA T* in respect of edge sharpness. You have to do a second look at the edges to detect the softening. In fact I don´t know any other binocular with that wide fov that have an edge sharp as the 7x42 FL. ‘’


AllBino’s.com [very good technical site for binocular reviews] 10 x 42 FL review

Astigmatism Properly corrected. 8.5/10.0

Coma Perfect. Minimal even at the very edge. 9.7/10.0
Blurring at the edge of the FOV The blur appears in the distance of 88% +- 4% from the field of view centre. 7.5/10.0

His complaints about the bin were distortion, not astigmatism or edge sharpness. Maybe we need a new thread to beat on the FL’s for distortion!
This site still ranks the 10 FL #1, with caveats.


So, there is some evidence that the Birdforum view isn’t universal…I’m not blind or delusional and maybe, just maybe, this perceived problem has been blown way out of proportion. I have no problem with those that opine about the FL’s shortcoming’s, but please don’t assume those opinions are universal or that others might have different experiences. From what you see above, there is a hugely divergent POV when it comes to these bins. Considering they have been [widely] considered the best roofs for 7 years now, they just can’t be as bad as some would like us to believe. The use of terms such as ‘’fuzzy edges, halo, distracting blur’’ is [IMO] intentionally derogatory and without merit. This comes from an owner and user, not a bystander.

And ,going back in time, it is very interesting to read about the EL’s [or Leica’s], which seem to have about the same edge performance as the FL’s, only it didn’t seem to matter for the El’s.

Same with the old Victories, best edge sharpness of the expensive roofs but, alas, in this case edge sharpness didn’t matter……….

james holdsworth said:

My FL's have no more fuzzy edges than any EL, Ultravid, Elite I have tested. And ''fuzzy'' is an exaggeration, more recently used as a pejorative than a description of the model.

I was out with my 10's today.......fabulous view as ever, especially in the gloomy overcast, no fuzzy edges just a bit of fall-off towards the periphery...if you force your eyes out there. Really, now, how is this different from anything else out there? [without field flatteners]

I have let many of my birding friends use my bins.......all have commented on the brightness and clarity, none have mentioned edge sharpness, none read this forum either, I would think or they would have been all over it!

Click to expand...

Well, here we go again. Some people notice the fuzzy edges, & are bothered by them (I’m in this camp), some notice them and aren’t bothered by them, & some (you, for example) hardly notice them at all. For those that are bothered by them, they’re a “fault”, for those that aren’t, they’re not. But they’re certainly “real” in the sense that people who notice & object to them see them in the FLs but not in the other alphas.

With regard to “fuzzy” being “pejorative”, of course it is, and-why shouldn’t it be since it refers to a phenomenon regarded as a “fault” by most of the people who notice it?

Anyway, I think we’ve probably said all there is to say on this tiny corner of the subject. And I hope you continue to enjoy your new binoculars. I’ll almost certainly be replacing my elderly Swaros in the not too distant future, but probably not with the FLs (because. . .I DON’T LIKE THE FUZZY EDGES).

Happily, the off-axis astigmatism in a star test can be photographed and as it happens I recently did some photographic experiments with rows of artificial star targets designed to graphically demonstrate the off-axis behavior of different binoculars.

The row of defocused pinhole artificial stars in the photos below show the aberrations and vignetting in the right half of the fields of two binoculars; one with astigmatism and one without. The edge of the field is on the right side. The photo on the left is a Zeiss 8x56 FL. The gradual change from round to oval shaped disks indicates increasing astigmatism toward the field edge. The photo on the right is a Nikon 8x32 SE in which you can see increasing vignetting (the vertical almond shapes) and field curvature (the shrinking size of the disk toward the edge) but virtually no astigmatism.

I'm perfectly happy for everyone to decide for themselves how subjectively important the astigmatism is, but it is there for all to see. That part is not debatable.

Henry:

Good of you to post some pictures of how many may see how some of these premium optics perform, when some real pictures deal with their performance.

I do see it like this, as I have found the premium Nikons and the Swaros. seem to
widen that sweet spot much further than some of the others. I like good edges.

And yes, that does make a difference in what optics I favor.

Jerry

fugl said:

So, to sum up this part of the discussion then, the FL’s “fuzzy edges” are not a “deliberate design feature” as some people (including myself) have assumed/asserted, but a simple fault. Is that a fair statement?

Click to expand...

No.

As I asserted earlier in the thread the Zeiss FL astigmatism at the edge of field (with low or zero field curvature) is an explicit design decision. One one Zeiss has been making since the non-FL Victory. Previously the design strategy seems to have been low astigmatism with field curvature at the edge of field.

I wonder if it's an strategy to remove field curvature given an increase in the average age of a binocular user. Or at least a recognition of accommodating the lack of accommodation amongst their older users.

Does the flat field (with astigmatism) change the perception of distortion when panning the field? Maybe that's another reason to make the change?

So there is a sort of logical progression from the old 3 element (Kellner and similar) eyepieces with both field curvature and astigmatism, to more complex EPs with field curvature and little astigmatism (you can see these in the current mid-range Chinese bins), to similarly complex EPs with zero (or little) field curvature and some astigmatism ("flat field"). Or in the SE case a little field curvature (right at the edge) and no astigmatism. And ultimately to no field curvature and low or no astigmatism ("sharp to the edge"). You can see before you get to nirvanha there are a range of field curvature versus astigmatism choices that can be made.

What decisions did Leica make with the Ultravid and Swaro with the original EL and original SLC? And Nikon with their LX L?

The reported differences are not assembly or manufacturing issues they're in the head of user. Different folks appear to have different sensitivities to this design decision.

fugl said:

With regard to “fuzzy” being “pejorative”, of course it is, and-why shouldn’t it be since it refers to a phenomenon regarded as a “fault” by most of the people who notice it?

Click to expand...

Because you don't prefix your opinion (and use of a loaded but ill-defined term fuzzy) with IMHO. You say "the bins are fuzzy at the edge" which is a universal statement. Of course that will wind up some Zeiss users

Do you only use "fuzzy edges" for bins with astigmatism at the edges? Not field curvature? I'm sure younger users will say "What blurry edges" but when you had the same bin with field curvature over to a older user they'll point out the "blurry edges". That's lack of accommodation but it's an observer dependent effect.

What about the Swaro ELs and Lecia Ultravids (or "Your favorite not sharp to the edge" bin)? Are they not fuzzy too? Or is "fuzzy" a threshold term for which you set the threshold.

Ultimately it's not a useful term. It doesn't convey any information other than you don't like the edges of the bin. Unlike say other reviewers. So the warning is people should try the bin to see if it works for them or not. Just like seeing the "rolling ball effect" in the SVs.

Henry: Very interesting photos. What other bins have you looked at with this technique?

Henry,
That's a nice demonstration of astigmatism. I wonder if the unfocused condition makes the red and blue fringing unrealistic somehow, but there it is, similar in roof and Porro. Oop, Ack, as Bill the Cat used to say.
Ron

ronh said:

Henry,
That's a nice demonstration of astigmatism. I wonder if the unfocused condition makes the red and blue fringing unrealistic somehow, but there it is, similar in roof and Porro. Oop, Ack, as Bill the Cat used to say.
Ron

Click to expand...

Ron:

This photo stream of Henry, shows much more than just astigmatism. I think it shows a nice visual of how the sharpness and sweetspot can vary between
optic designs. It shows how the Zeiss FL compares to the less distorted Nikon SE.


I, as a youth had astigmatism, and my eyeglasses had to be corrected each time to correct the problem.

For me, now that I have corrected vision without eyelenses, I am free to
appreciate a view through binoculars without any issues.

So that means, I like the Nikon view, along with the Swaro. EL and SLC, and how they offer a pleasing view, better edge performance and that is what many prefer.

Give me the best, flat, undistorted view that the optic will allow.:t:

I do not want any added astigmatism that the engineer could prevent.

Jerry

Kevin Purcell said:

No.

As I asserted earlier in the thread the Zeiss FL astigmatism at the edge of field (with low or zero field curvature) is an explicit design decision. One one Zeiss has been making since the non-FL Victory. Previously the design strategy seems to have been low astigmatism with field curvature at the edge of field.

I wonder if it's an strategy to remove field curvature given an increase in the average age of a binocular user. Or at least a recognition of accommodating the lack of accommodation amongst their older users.

Does the flat field (with astigmatism) change the perception of distortion when panning the field? Maybe that's another reason to make the change?

So there is a sort of logical progression from the old 3 element (Kellner and similar) eyepieces with both field curvature and astigmatism, to more complex EPs with field curvature and little astigmatism (you can see these in the current mid-range Chinese bins), to similarly complex EPs with zero (or little) field curvature and some astigmatism ("flat field"). Or in the SE case a little field curvature (right at the edge) and no astigmatism. And ultimately to no field curvature and low or no astigmatism ("sharp to the edge"). You can see before you get to nirvanha there are a range of field curvature versus astigmatism choices that can be made.

What decisions did Leica make with the Ultravid and Swaro with the original EL and original SLC? And Nikon with their LX L?

The reported differences are not assembly or manufacturing issues they're in the head of user. Different folks appear to have different sensitivities to this design decision.

Click to expand...

Deliberate design feature. The issue here, I guess, is whether edge fuzziness is something the designers let through because they thought it was too unimportant to spend time & money correcting or whether it was a more or less inevitable consequence of the pursuit of some other goal, e.g. superlative center sharpness. I have no idea which of these 2 alternatives apply in the Zeiss case, or even if they are legitimately posed in the clear-cut way I have done. But be this as it may, my reading of the posts immediately before my last, was that the first alternative was being favored & I was simply asking in my post if this impression was correct. So far no answer (but fair enough, maybe not a sensible question).

Kevin Purcell said:

Because you don't prefix your opinion (and use of a loaded but ill-defined term fuzzy) with IMHO. You say "the bins are fuzzy at the edge" which is a universal statement. Of course that will wind up some Zeiss users.. . .

Click to expand...

Here’s the relevant portion of my original post on the subject:
“When I compared the Zeiss 8 x 32 with its Swarovski & Leica equivalents at Eagle Optics a few months ago, I found the fuzzy edges of the Zeiss quite noticeable & quite distracting.” How you get a “universal statement” out of what is obviously a mere statement of personal perception is beyond me. I do, however, plead guilty to underestimating the strength of brand loyalties & the passion with which many people respond to even a hint of criticism of their favorite toys.

Anyway, as a layman with no knowledge of optical science at all, I always enjoy these discussions--& generally learn something from them--however silly and arcane they sometimes appear to me to get at the fringes. So, keep it coming!

Kevin Purcell said:

No.

As I asserted earlier in the thread the Zeiss FL astigmatism at the edge of field (with low or zero field curvature) is an explicit design decision....

Henry: Very interesting photos. What other bins have you looked at with this technique?

Click to expand...

Kevin,

In this case "zero field curvature" is a kind of mathematical fiction. The midpoint between the tangential and sagittal foci may be close to the plane of central focus, but good focus can't be achieved at the field edge at that midpoint because the two foci are so far apart. If you place a star point at the field edge the best focus of it will look like a little cross with bars of equal length (the midpoint between the foci) but it cannot be focused to a point.

The photos were an experiment to see if I could find a way to "track" the progression of off-axis aberrations in a single photo. I only tried those two binoculars because of their different off-axis profiles. Any static image, however, will fail to show just how dynamic and variable the aberrations and vignetting are when the eye is looking through the binocular and roaming around the field. Try looking at a single defocussed star point and move it around the field to see what I mean. It's no wonder people can't agree about what they see.

Ron,

Yeah, this isn't the best way to image lateral color. Since the out of focus colors form only on tangential edges the white bar target works much better.

Henry

Here's one more set of photos that might make the effects of astigmatism clearer.

The first three photos from the left show a lined piece of paper positioned near the bottom edge of the field in a Zeiss 8x56 FL (notice the curved fieldstop at the bottom). What happens to a target like this in the presence of astigmatism is that the vertical and horizontal lines cannot be brought to sharp focus simultaneously. The first photo on the left shows the tangential focus (horizontal lines focused), the second photo shows the sagittal focus (vertical lines focused) and the next photo shows focus set at the approximate midpoint between the two (best focus) where really neither set of lines can be sharply focused. In this case "best" focus at the edge is close to the plane of center focus, but it's not very good because of the astigmatism. The photo on the right is the same target positioned near the bottom edge of the field in a Nikon 8x32 SE at best focus. In the absence of astigmatism both sets of lines can be brought to sharp focus, but in this case "best" focus at the edge is about 3 diopters away from the plane of center focus due to field curvature.

I would have to keep my comments to only the 10 FL, as it is the only model I have any significant experience.

But I find it intriguing that the only site that has imperical data for astigmatism [Allbinos] rates the 10 FL nearly identical [for astigmatism] as the EL and the Nikon HGL. Assuming the methodology isn't flawed, it seems fair to say that these three bins share similar characteristics. Is that a fair assumption?

And, if so, why are there not numerous threads discussing the astigmatism of those models as well?