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Binos with or without field flatteners (1 Viewer)

Hi Peter,
Scopes have longer focal length and slower objectives than binoculars.
Also interchangeable eyepieces.

They differ from binoculars.

My Nagler 82 degree eyepieces are very flat field on some of my astro scopes.
 
Canon advertise their IS binoculars, even the 2nd or 3rd tier 8x25 IS, as having field flatteners. They are much less than $1,000.

The specs state doublet field flatteners for the 8x25 IS.

I thought that the smaller Canon IS binoculars had single field flatteners and the larger ones doublet field flatteners.

Sometimes makers get the specs wrong so I don't know if the 8x25 IS actually has doublet field flatteners.

P.S.
I think that Canon IS binoculars have had field flatteners from the late 1990s.
 
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After reading the above, I still do not understand why most manufactures are now including the field flatteners? If edge to edge sharpness is not dependant on FF, then why add the complexity and cost? Is it because edge to dge sharpness does not ensure depth of field sharpness due to closer focusing and due to wider FOVs in modern binos? Therefore field flatteners are added?

In other words, is petzval field distortion a great problem now and it is being corrected? Or maybe the problem is not greater but the expectations are greater?
 
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Hi,

in binoculars with their very fast and short focal length objectives field curvature is quite pronounced (because of short focal length) and depth of field is very shallow (because of fast focal ratio) so in order to get edge to edge sharpness over a wide true field of view, field flatteners are very much necessary.

In slower instruments with longer focal ratio, field flatteners might not be necessary at least for visual use. For deep sky astro imaging, flatteners are being used most of the time.

Joachim
 
Hi,

in binoculars with their very fast and short focal length objectives field curvature is quite pronounced (because of short focal length) and depth of field is very shallow (because of fast focal ratio) so in order to get edge to edge sharpness over a wide true field of view, field flatteners are very much necessary.

In slower instruments with longer focal ratio, field flatteners might not be necessary at least for visual use. For deep sky astro imaging, flatteners are being used most of the time.

Joachim

Thanks. I understand these points which seem to make sense. Begs the question why I should consider a new pair of 8x32 without field flatteners? Given the fact that I am not sensitive to rolling ball issues.
 
Finished with salespeople.

I can certainly appreciate that sentiment; there’s a big difference between 20 years of experience and one year of experience 20 times. If you took all the optics "salesmen" I’ve seen in the town I live in now, and parted them out, you couldn't come up with enough usable parts to build one knowledgeable tech.

But, it has been my experience sweeping statements as such as that (based on even a preponderance of evidence) CAN—although certainly not always—be a recipe for regret. All rocks are certainly not diamonds. On the other hand, one should not see all diamonds as stones. Just a thought. :cat:

Cheers,

Bill
 
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I can certainly appreciate that sentiment; there’s a big difference between 20 years of experience and one year of experience 20 times. If you took all the optics "salesmen" I’ve seen in the town I live in now, and parted them out, you couldn't come up with enough usable parts to build one knowledgeable tech.

But, it has been my experience sweeping statements as such as that (based on even a preponderance of evidence) CAN—although certainly not always—be a recipe for regret. All rocks are certainly not diamonds. On the other hand, one should not see all diamonds as stones. Just a thought. :cat:

Cheers,

Bill

After some time at Annopolis, I would never question the wisdom of a Chief Petty Officer. Let me know when you are in town and I will show you some local birds or at least feed you some aged bourbon.
 
Thanks. I understand these points which seem to make sense. Begs the question why I should consider a new pair of 8x32 without field flatteners? Given the fact that I am not sensitive to rolling ball issues.

The question is, do you need a field with edge-to edge sharpness - in my opinion it's not a necessary feature for a birding binocular (see my earlier post in this thread on it). In fact my favorite bin, the E2 8x30 has a huge field of view with a nice and large sweet spot, but not sharp to the edge. I don't miss it.
Comparable options with field flattening in 8x32 are all a bit narrower (and sometimes quite a bit more expensive).

Joachim
 
Thanks. I understand these points which seem to make sense. Begs the question why I should consider a new pair of 8x32 without field flatteners? Given the fact that I am not sensitive to rolling ball issues.

I have two binoculars with field flatteners and several more without. Which I use depends on where and when I'm birding. I try to pick the best tool for the job. Round here that would be one of the curved field designs about 60% of the time (and it's not just because they have the sharper edges. ;))

David
 
...Nikon, the leader in this field, has had binoculars with Field Flatteners since about 1998 in their top ranked binoculars beginning with their now discontinued SE Porro Prisms: The 8x32 SE, 10x42 SE and 12x50 SE... ...Nikon also started using FF's about 2001/2002 in their (now discontinued) top of the line Roof Prism HG and HGL series and continued it in their current EDG Series since 2008...

In fact, Nikon has been using field flatteners in their best porros and roofs starting _long_ before 1998 and 2001.

For example, the Nikon 7x50 ProStar (porro), 10x70 Astroluxe (porro), and 8x40 Classic Eagle (roof), all use field flatteners. They were all introduced in ~1984. Fuji has also long used field flatteners. I suspect use of flatteners may go back decades earlier, but those are the earliest models with which I have experience. My first serious birding bins were the 8x40 Classic Eagle, which to my eye were clearly superior to the Zeiss and Leica competition until introduction of phase coatings by those companies in ~1988 tipped the balance of overall optical quality to their favor. Still, I missed the big easy flat sweet spot of my Classic Eagles for many years (during which I used Zeiss 7x42 BGATP as my primary birding bin) and have only been fully optically satisfied since Swarovski put it all together in the 8.5x42 EL Swarovision.

--AP
 
I wouldn't worry one way or the other....The flatteners are more a current fad....


19 “IT’S ‘TACK SHARP’ FROM THE CENTER TO THE EDGE.”

More than one knowledgeable observer has praised his binocular for providing “tack sharp” images from the center to the edge of the field. However, those who make such claims don’t have the capacity to observe images on axis and at the edge of the field in the same instant.

The observer may see a “crystal clear” image in the center of the field, then, on seeing an equally crisp image at the edge of that field, supposes all points in between must provide images of equal sharpness, all the time. But to the brain, it just isn’t so.

A Reality Check


Concentrate on the tiny space between “image” and “in” in the preceding paragraph. If you’re unwavering in your concentration, you’ll notice the most you can make out are those two words; some people can’t even do that. Now, with your eyes frozen on that tiny space, try to see the “r” in “clear” or the “c” in “center.” Although the separation in this example is far less than one would find in a binocular’s field of view, it’s plain to see our sharply focused field is very restricted, not by the physical optics of the binocular but by physiological optics controlled by the brain.

An observer with a high quality instrument can easily come away with the wrong conclusion because he’s not paying attention to the millisecond eye movements that place the edge of the binocular’s field of view in the center of his own or the slight dioptric accommodation that accompanies that movement.

A Talk with an Optometrist

Wanting to be certain not to share more than I know about this subject, I called on optometrist, Dr. Edward R. Ford, of Ford Family Eye Care in Twin Falls, Idaho who offered the following:

“The corneal thickness centrally is thinner than it is peripherally, thus causing a change in refractive error from the eye’s central line of sight to its peripheral line of sight. Now, aside from the optics of the cornea, aqueous, pupil, lens and vitreous not being perfect, perhaps the largest issue with the eye’s peripheral vision lies at the level of the retina.*As you know, the retina consists of photoreceptors called rods and cones. The rods provide light sensitivity and motion detection, while the cones provide the detail and color vision. The center of the retina, known as the macula, consists of the highest concentration of cones while the peripheral retina has the higher concentration of rods. With that in mind, it makes sense that the central retina or macula gives us the sharpest acuity, while the peripheral vision does not.”

This explains the value of the millisecond eye movement and dioptric accommodation that most observers never consider.*:cat:

Just a thought,

Bill
 
Thanks. I understand these points which seem to make sense. Begs the question why I should consider a new pair of 8x32 without field flatteners? Given the fact that I am not sensitive to rolling ball issues.

Which also begs the question: why would you restrict your choice to those 32s with field flatteners unless you insist on edge to edge sharpness?

Personally I put the subject in the middle of the field of view so don't feel that field flatteners are any advantage for me. I have Zeiss SFs and have occasionally tried to let my eyes roam around the field of view, as described by field flattener enthusiasts and found this to be unnatural and uncomfortable, but you may have a different opinion.

Edge to edge sharpness sounds like a great thing to have but I have yet to encounter a field flattener-equipped bino that is actually as sharp at the edge as it is in the centre even though the edges were definitely sharp. In this sense at least the phrase 'edge to edge sharpness' is misleading as it suggests uniform sharpness across the whole field.

However, lots of folks seem to derive pleasure from field flatteners so give them a try, but stay open minded and try binos that aren't so equipped.

Lee
 
Hi,

Bill has a good point here - field curvature will also be counteracted by the eye's ability to focus. This means that different users will perceive sharpness in the field differently, depending on their eyes' ability to focus.

It is quite possible that one user perceives an instrument as sharp from edge to edge while another user, perhaps after cataract surgery, sees a not too large sweet spot.

Also field flatteners only counteract field curvature - there might be other uncorrected aberrations like coma or astigmatism present near the edge of field, which might limit edge of field sharpness despite a perfectly flat field.

Joachim
 
There is a proclivity for observers to blame every anomaly they experience on the instrument and not on physics or their physiological inability to accommodate for those anomalies. This indicates they (at least the optically inexperienced) think their vision is flawless and any problem seen MUST relate to the performance of the binocular. The optical instrument gets consistently blamed for retinal scarring, macular pucker, cataracts, premature glaucoma, and about 20 more problems of the eye. It’s really sad that folks who spent SO MUCH of their time making mountains out of mole hills will spend SO LITTLE time studying the material required to understand those mole hills or that compensation for virtually every problem they bellyache about could be solved by reaching a little deeper into their pocket.

In addition, in the evening, the eye can operate with an f/ratio of about f/4. During the day, it can be stopped down to about f/11. Curious observers should ask a professional photographer, or serious amateur astronomer, which focal ratio provides the sharpest image.

I wouldn’t change anything, in that discussions approached from different angles, can be quite enlightening to the honest truth seeker. For me, it’s a two-edged sword. I would like to see the bar of understanding raised so that we could move forward a little quicker. However, by the nature of binocular forums—with old-timers leaving and newbies arriving—that process can’t happen until the public comes to grips with more optical realities. :cat:

Just a thought,

Bill
 
After some time at Annopolis, I would never question the wisdom of a Chief Petty Officer. Let me know when you are in town and I will show you some local birds or at least feed you some aged bourbon.

Was it the chevrons, or that they were gold instead of red, or the Cooke triplet in the middle. Anyway, it is always good to see an osofer who recognizes his superiors.

Now, with my dig out of the way (I’ll probably be taken by some to be serious ... COMMA again): Please, as an officer in MY navy, QUESTION everybody. You may not have the ability to voice those questions, but they should be turning over in your mind. Many of the terrible things they said about little Georgie Patton were true. But, Roosevelt, Stimson, Marshall, Eisenhower, Bradley, and even Churchill recognized him as the most productive general in either army. And why? Because he questioned and would never let a problem go unsolved. A lesser leader would have been crucified because of some of his many Faux Pas. But, they ALL agreed he must be kept at all cost. Even General Fieldmarshall Kesselring said Patton was the ONLY general in the whole American army to strike fear into the German High Command. For example, for all of Montgomery’s bluster about striking “hard and fast,” Patton told Eisenhower and Bradley during the PLANNING for overlord that Monty would NEVER make his stated taking of Caen in the time he projected. Knowing Montgomery, his take on warfare, the terrain, the obstacles, and the enemy this master tactical expert questioned constantly. And while being harsh for the right reasons, history shows, on so many occasions, he OUT THUNK the thinkers!

As far a coming to Seattle, I thank you for your kind offer. But I have traded my Stellers Jays, Northern Flickers, and French fry fed Seagulls for Magpies, Killdeers, and Prairie Falcons. You can keep the “Aged Bourbon,” but, I sure could take a not-so-aged ... Coke. :cat:

Where do you live?

Blessings,

Bill
 
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For binos I have Nikon 10x42 HG (originals with leaded glass and aluminum body- heavy), Lieca 8x32 BA (my wife's fav), Swaro 8.5x42 EL and a 80mm Swaro ATS scope.

Might be looking to upgrade my Lieca 8x32 BA to something more modern. I have researched allbinos and here.

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Begs the question why I should consider a new pair of 8x32 without field flatteners? Given the fact that I am not sensitive to rolling ball issues.

If you are going to replace the Leica 8x32 BA with field flattened bins, the only two options among the alphas are Swaro SV 8x32 and Nikon EDG 8x32 . There is no 8x32 in Zeiss SF and Leica thinks field flattening is for suckers. Between Swaro and Nikon, most would agree Swaro is the better choice. Some think Nikon is better. I have used the SV 8x32 FieldPro for close to a year and am still impressed by it. My other pair of Leica UVHD 10x42 is dear to me and I tend to use the Leica more for the reason I am mostly birding close to a lake for better reach. If I can only have one pair, the SV 8x32 would be my choice. The handling, eye relief, light weight, fov all make it almost perfect. Using both the flat field SV and regular Leica I have hard time adjusting my eyes to see objects in the edge of the field. It strains my eyes doing that. I tend to only look at objects in the center field.
 
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Hi,

don't forget the SE 8x32 - sometimes available used and a lot cheaper than Swaro or EDG. Very nice glass... not waterproof though and doesn't look like much - which might also be a good thing depending on where you are...
Don't have a one to one comparison with Swaro but had my SE 10x42 along some day and we compared it to a fellow birders Swaro 10x32 - in that admittedly unfair comparison it fared quite well.

Joachim
 
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