Brock, I suppose what Bryce and others were referring to was that distortion is a complex phenomenon with myriad aspects to be considered. The two referred to here are a linear average of the distortion through the entire FOV (represented by a k-value) and the variation in the distortion pattern through the FOV.
Dr Merlitz's fine representations of the theoretical impression of various k-level distortions offer a great tool for understanding distortion but they do not necessarily represent what one experiences when one looks through a particular pair of binoculars, amongst other reasons because distortion through the FOV is very rarely linear. One can see this in the ELs, the Z SF and a plethora of other examples. The trick is to find the right set of compromises through the entire FOV; not only in the pattern of distortion, but also with myriad other image factors. Optical design is a sticky spider web of complexity and unfortunately it seems a cultural misunderstanding of seeing distortion as a largely independent factor within an optical design has developed. One does not simply design an optical system around distortion and see what comes out in the other optical parameters (or vice versa): changing either the overall linear distortion or the distortion pattern would always result in positive/negative effects on many other optical parameters, sometimes critically (it is not just a simple screw that one can twist and adjust at will). FOV, edge sharpness, centre field sharpness, CA, eye relief, tangential field curvature et alia are all integrally linked.
I beg of you: please, pretty please, try a variety of optical products yourself, including the ELs and the SFs before continuing to knock them or any other expression of distortion. Try to do it with an open heart and an open mind, and take your time to do it so that you can really get a feel for what they might be like in the field under real conditions (maybe a store owner will allow you to walk around a little for counters are notoriously bad places to test optics because we "test" them in a seemingly completely logical but invariably artificial and unnatural ways at a counter). I am sure that many on birdforum, my colleagues at other companies, and I would all read about your real world experience with great interest as we all benefit from the insight, thoughts and ideas shared here.
Theoretical insights and second hand experiences can be very useful but nothing beats personal experience: if one has never tried Asian food then no amount of stories, ingredient lists or images will ever really help one understand what a Thai Green Curry tastes like (a crusade from someone who has read the bible is way more believable).
Dale,
Thanks for your comments. I think if you've had spicy Indian curry dishes, you have a pretty good idea of what Thai curry dishes taste like, I've had both and they are similar to my tastes buds. Similarly, I know that very low distortion bins cause me to see RB, although I'm trying to understand your point about how the "other optical parameters" might impact whether or not one who is susceptible to RB sees it in a bin.
My "cultural understanding" is that if a person is very sensitive to RB, and his k value falls in the mid moderate distortion band, all these "other optical parameters" can't compensate and make a bin who k value falls below .085 such as the 8.5x SV EL workable for him, though perhaps they could influence a bin that's on the borderline of k=0.7 like the SFs or even a bit more like the 8x32, 10x50 and 12x50 SV ELs. I don't know what those "other optical parameters" are or how much they can influence one's perception of RB in low distortion binoculars. You're the first person to mention that, and you seem to be implying that those "parameters" can influence one perception of RB independent of what the bin's k-value is, is that what you're saying?
From my POV, if some people see RB in the 8x42 SF model, that means that others will, too. I don't think it takes an optical engineer to figure that out. But like the SV EL, most people won't see it or will adapt, so I don't think they have any worries about RB in the SF affecting sales, particularly from my comments on BF. But Swaro might if the SF catches fire.
Besides which, unless those other optical parameters
increase the perception of RB, Zeiss should have nothing to worry about since the SF's k value is near the borderline of k=0.7, which is head and shoulders above the 8.5x and 10x SV ELs, so most people will be able to tolerate it.
However, from what you wrote above it sounds like you are saying that the SV EL or were you referring to the SF was designed without regard for its distortion level, i.e., "One does not simply design an optical system around distortion and see what comes out in the other optical parameters (or vice versa)".
Surely the optical engineers at Swarovski and Zeiss know what happens when you pour all the optical "ingredients" together in the "soup" what the final result "tastes like," and that it's not just a trial and error process?
It would be helpful to me, and I think others, if instead of being abstract, you explained in more detail what you mean by this, that is, how binoculars are designed with all the "parameters" you referred to taken into consideration, how they affect each other, and most importantly, if how they balance out were part of that design process with the SV EL, with the end result in mind that the optics would produce smooth panning for most users?
It was Carl Zeiss Jena that first introduced pincushion into the design of binoculars in the 1940s for the expressed purpose of making panning smoother, but other optics makers including Swarovski soon followed suit.
As to trying an SF or SV EL, I live in rural area without large stores such as Cabela's so it's hard to try an SF even if they were already available. However, there is a Swaro dealer that's closer. It's about a 120-mile-trip to the nearest store that might carry the SF and Kowa, already tried the LXL/Premier. It probably won't be until late spring of 2015 before I even have a chance to try an SF (provided there aren't further delays). Meanwhile, all we have to go on are the reports of the fortunate few who have had the privilege of trying one of the prototypes.
And to clarify your comment, there really aren't a "variety of optical products" with low distortion to try. AFAIK, only Nikon (HGL), Kowa (Genesis), Swaro (SV EL), and now Zeiss (SF), and each make only one binocular series with low distortion. I think there are also some military binoculars, too, with low distortion, but they have IF EPs and reticles, and are not useful for birding.
As Holger wrote:
"Most binocular manufacturers followed Zeiss' example, so that by the Mid 1950s a certain amount of distortion, according to the "angle-condition", had become the new industry standard. ....
"About 2005, a few manufacturers began to re-introduce binoculars with very low distortion, the Japanese Kowa and Nikon among them. The globe effect, virtually forgotten over the decades, was thus raising its head once again, yielding an unpleasant panning behavior of these binoculars and promoting motion sickness with some of the rather sensitive observers.
"Swarovski began to experiment with low-distortion binoculars along with their introduction of the Swarovision line in 2008. User reports about the emergence of the globe effect in these binoculars were contradictory. In short, it was getting time to understand these phenomena better, and I intensified systematic studies and computer simulations of these effects, which I had begun in 2005. The results of these studies have subsequently been published in a scientific paper [4] and are also discussed in detail in my recent book."
I'm glad he brought this issue to the fore, and in a scientific manner, since I have been trying to raise awareness of this and getting a lot of static for it, and apparently, still am, but I think this should not be "swept under the rug," and that it should be known that the binoculars mentioned above represent a departure from past designs, and it remains to be seen whether or not people will like that in the SF or prefer it over the SV EL.
I'd have to sell "the farm" to buy either one, and I'd really miss my animals.
Lastly, I'd like you to either or confirm or deny what Holger and Pier have said, namely, that Swarovski has been increasing the amount of distortion (or in your new parlance tweaking those "other optical parameters") to make panning smoother for more users in the SV ELs? Yes or No?
Brock
