I had this in the optics thread, but it was suggested I post it here. This is concerning binoculars mostly, I've been reading and trying to edumicate myself a bit on optics. I've come across this field flattening terminology that sounds like a bunch of physics and engineering speak for edge to edge clarity. Is that all it refers to? From what I read, it seems Swaro is about the only brand to offer it in their lenses. Obviously it doesn't refer to a lack of perceived 3d image as that is what stands out to me when I look through a set of Swaro's. I don't own any myself, but I'm saving to upgrade at some point. Thanks for any all help for my ignorance.

In a nutshell, yes it allegedly offers more edge to edge sharpness. In my slightly humble opinion Swaro got carried away with the whole field flattening thing about 15 years ago and that contributed to the "rolling ball" effect in some of their models of binos during that era. Swaro apparently backed off a bit on the field flattening and resolved the issue.

I'm pretty sure other optics manufacturers also have field flattening coatings, they just are not as vocal about it as Swaro.

In most optics, flatness of field refers to the shape of the object plane vs. the shape of the image plane. For example, many camera lenses will render objects that are on the inside surface of a sphere (i.e., everything 20 feet out in front of the lens) into a flat field at the film or sensor. An enlarging lens is flat field (the film negative) to flat field (the photographic paper). Some lenses have a poor design, and image the inside surface of a sphere (everything 20 feet out in front of the lens) into a spherical surface at the sensor. With that arrangement, you can get the edges in focus with the center blurry, or you can get the center in focus with the edges blurry.

Rickshaw,

Image flattening also depends on the individual viewer's eyes. Everybody's eyes differ in various ways, including color perception, astigmatism, etc., and tend to change as we age. As a result, the "rolling ball effect" is more apparent (and can be a problem) for some people, and not others. Which is why it always helps to actually look through various binoculars, if possible, before you buy one.

I don't consider myself particularly susceptible to the rolling ball effect but several different examples of 8x30 and 8x42 SLC's of about 15 years ago practically made me seasick after a couple minutes of looking through them, especially the 8x30's.

A friend had some 8x32 Victory's about 10 years ago that had slight rolling ball effect to me, but was much worse for him. He ended up selling them.

The rolling ball effect is geometric distortion, barrel distortion to be exact. It makes the image look like it is on the surface of a sphere. This effect comes from an inexpensive ocular lens design.

Flatness of field is a different effect. It has to do with whether the real image formed by a lens lies in a flat plane, so that it can all be in focus at once on a flat sensor.

Two different, but easily confused effects.

denton,

That was one of my points. Geometric distortion is also affected by the sensor--which can vary considerably in human eyes, cameras, etc. In eyes, part of the "problem" is yet another lens (the eye's) between the optic and the image plane--which itself is not flat.

It's also affected considerably, in "viewing" optics or photography, by the diameter of the exit pupil or f-stop.

So, is there a particular element in bino's that provides a better 3d depth of field (if that's the proper term) or does it come from sharpness and color rendition. I appreciate the advice to go look at a bunch and see what my eyes like. It seems binoculars have come a long way in the past 20 years.

The farther apart the objective lenses, the more 3D effect. Which is one reason full-size Porro prism binoculars still have some optical advantages, despite the nearly universal switch to roof-prisms since the phase-correction coating revolution of 30+ years ago.

That's interesting because those binos aren't flat field optics.

A good question and I would like to know the answer also. As I mentioned in previous threads, I have updated 7x30 and 8x30 SLC's. The 7x30's SLC's have always been noted for their excellent 3D image, and is noticeably better than the 8x30's. This was true before and after the updates. The 8x30's also have new and improved (according to Swaro) prisms, while the 7x30's kept their original prisms. Both have new dielectric coatings on the prisms, new coatings on the objective lens, 4th gen eyepieces.

I can't recall if Swaro was advertising their field flattening coatings at the time, but the last year or two of the 3rd gen and the first year or two of the 4th gen 8x30's had the rolling ball effect more apparent. I looked through a number of different examples at that time and they all seemed to have it. The last few years of 4th gen production I stopped seeing the rolling ball effect. Later I read where Swaro did change the coatings (I believe I first read it on BVD).

Thanks for the responses guys. I appreciate your knowledge and willingness to share.

The field flattening is done with an special lens element introduced in the light path, in other words, yeah it's another lens. I burst out laughing when I read that it was done through coatings and it took a while to clean the coffee off my 4K display and my keyboard. What a mess.

Edited for typo. I hate typos.

Lens coatings have nothing to do with whether or not an optic has field flattening technology, zero.

Although I believe I understand most of the terminology and some of the technology I try to ignore it and the add copy as much as possible and just see how a bino looks to me. Rolling Ball or lack of edge to edge clarity will be obvious with just a quick look. If possible try to do side by side comparisons ideally in lower light and at longer distances, which is not always possible in a shop setting. Borrow from friends if possible.

I got good binos thinking it will compensate for aging eyes, it does some but not as much as I had hoped. Also with less than perfect vision (used to be 20-20+) the differences between the good and really good binoculars is less apparent, this opens up a huge market of good but not necessarily the Alpha binoculars. This is a good thing especially for back up binoculars.

I answered your thread in the optic's section, but thought I'd cut and paste it here too...

Correct. It's the glass grind.

Brad, JG, FTR,
No it is not exclusively glass. I had this conversation with Swaro a few years ago when I mentioned field flattening lens, and it was politely explained to me lens coatings are part of the equation. Although I was wrong to omit lenses are part it too.

No offense, but you need to accept the fact that on this subject you have no idea what you're talking about and neither did this mystical Swaro guy. Field flattening tech wasn't introduced into Swaro Optics until the Swarovision, a new optical design for Swaro, which debuted around 2010.

JG,
Lot of folks know more about optics than I do, but the between the internet and the Swaro tech I spoke to I have to go with the mystical swaro guy. Everything I have listened to says coatings are part of the equation with field flattening.

Got any links to those internet articles backing up your claim?

Hi Casey, it's the shape of the lens, or glass "grind". Coatings have essentially nothing to do with it. IIRC, they're using a type of aspheric lens for Swarovision(?).

Also, I think you're misunderstanding what "Rolling Ball" is (it's actually called "Globe Effect). I think based on your comments perhaps you're mistaking "Pincushion Distortion" for Globe Effect. As I understand it, Swarovison's lens is designed to eliminate most of the Pincushion Distortion commonly found in normal binoculars in order to achieve a flatter, sharper edge-to-edge field. The result from this optical choice is Globe Effect.

A good read on "Globe Effect" (aka rolling ball): https://en.wikipedia.org/wiki/Globe_effect

Types of distortion: https://en.wikipedia.org/wiki/Distortion_(optics)

Regardless, it's even on the Swarovski Website:

"The SWAROVISION technology redefined the concept of optical quality. Field Flattener LENSES provide unprecedented peripheral definition, fluoride-containing HD lenses minimize color fringing, while optimized coatings ensure maximum color fidelity. Large eye relief offering a full field of view for those wearing eye glasses."

https://www.swarovskioptik.com/about_swarovski/innovations#

I am by no means even remotely expert on any of this... I just know that when I use Swarovision Binoculars I start feeling unsettled (Globe Effect). In the early models it seemed particularly bad. As I said, I did use a 10x42 the other day and it seemed much better. However a few days after I tried the 10x42's I used an 8x32, and it it was a very bad experience! My Leica 8x32's have a far more "relaxed-natural" feeling when using them, even with some pincushion distortion present.

As the old preacher said, "it's better felt than telt."

Cheers My Friend!