Is a flat field part of the "Alpha View" ? (1 Viewer)

The reason I ask is that the Nikon SE series has one of the most highly regarded images available at any price, yet the distortion figures are at best middle of the road. How much pincushion does it take to get rid of the rolling ball effect ? The attached thumbnail shows some stats from AllBinos.

Thanks
Bruce

bh46118 said:

The reason I ask is that the Nikon SE series has one of the most highly regarded images available at any price, yet the distortion figures are at best middle of the road. How much pincushion does it take to get rid of the rolling ball effect ? The attached thumbnail shows some stats from AllBinos.

Thanks
Bruce

Click to expand...

Useless data. Ignore it.

Does an alpha have to be flat to be considered an alpha? The answer is no if leica ultravid hd and zeiss fl are considered alphas. Both make straight lines bend more than the EDG and SV (if this is what you mean by flat (see Henry's post below). They are all nice, but have different qualities and feel to them.

The hgl or lxl has a very flat view as well.

Don't get too caught up in reviews, try glass and you decide which is best. If you feel glass xxx is the best, then it is.

"Flat Field" needs at be better defined here.

If by "flat" you mean a field without field curvature that means that objects at the field edge and at the center are in focus simultaneously. It has nothing to do with the rectilinear distortions (pincushion, barrel). Those bend lines toward the field edge, but don't affect the focus of the lines. Angular magnification distortion compresses objects at the field edge (even when lines are perfectly straight) but also doesn't affect focus.

The "globe effect" or "rolling ball" is a subjective psycho-visual phenomenon associated with panning an optic that has angular magnification distortion. AMD is minimized by applying enough pincushion distortion to restore compressed objects to something closer to their undistorted shapes. Individuals differ as to how much pincushion is needed or if it's needed at all.

The "flat field" is not usually an "Alpha" charateristic.You need to get an Alpha Plus, like one of the SE's for that, 8-P

Hi Henry

What I'm referring to is the bending or bowing of the image of building roofs, telephone poles, or basically any horizontal or vertical object at the outer edge of the FOV.

Thanks
Bruce

henry link said:

"Flat Field" needs at be better defined here.

If by "flat" you mean a field without field curvature that means that objects at the field edge and at the center are in focus simultaneously. It has nothing to do with the rectilinear distortions (pincushion, barrel). Those bend lines toward the field edge, but don't affect the focus of the lines. Angular magnification distortion compresses objects at the field edge (even when lines are perfectly straight) but also doesn't affect focus.

The "globe effect" or "rolling ball" is a subjective psycho-visual phenomenon associated with panning an optic that has angular magnification distortion. AMD is minimized by applying enough pincushion distortion to restore compressed objects to something closer to their undistorted shapes. Individuals differ as to how much pincushion is needed or if it's needed at all.

Click to expand...

Despite the figures given on allbinos the SE series does not have a lot of pincushion, just the right amount for me. Arek (allbinos' main reviewer) prefers bins with very low distortion.

But that's not a good thing if you are sensitive to RB. Plus, to my eyes the first curved line in the 10x42 EDG does not start 88% from the center. I've tried it and if it had that low a distortion level (lower than the LXL, according to allbinos), birds would have been rollin', rollin', rollin'... and they weren't.

As Henry pointed out above, "flat field" and rectilinear distortion levels are independent of each other.

So you have a nice flat field with the SE series, but also enough pincushion to make panning smooth for most people (haven't heard too many complaints, but some people have reported seeing some mild RB with the SEs, but not nauseating projectile vomiting RB like the full sized HGLs.

Saturday, I compared a Nikon 8x40 Action porro to my 8x32 SE. The Action has more pincushion and there's a "rolling bowl" effect from the distortion (pincushion) at the edges. I didn't see this with panning the same features (tree lines, houses) with the 8x32 SE. I do see some mild RB while panning with my 10x42 SE, but it's not distracting to me.

I also tested the "bow" with a telephone pole and straight lines in the Action started curving earlier and reached a steeper curve at the edges than the 8x32 SE. So you can have too much of a good thing with pincushion too.

Pincushion "rolls" the image over a negatively curved surface while AMD (angular magnification distortion) "rolls" the image over a positively curved surface For those sensitive to these effects, the outcome is similar, a perception of a rolling motion while they pan.

For me, bins that have AMD and pincushion balanced well so that I can pan smoothly without any distracting motion are the ones I like best. Since people have different levels of distortion in their eyes, how much distortion it takes to achieve that for them might differ from what level it does for me. YMMV.

Leica Ultravids don't have a flat field, but they are "alphas". The FLs have astigmatism at the edges. Only Swaro SV ELs and Nikon EDGs have flat fields at the alpha price point.

So the answer to your question is that presently, "No," flat fields are not synonymous with the "alpha view".

Also, RB is not a "given" to achieve a flat field view. The EDG and SE both prove this. There's a small trade off in that the the EDG and the SE aren't sharp to the very, very edges like the SV EL and the Nikon HGL, but as Henry mentioned, taken to the extreme, the SV EL and HGL compress objects at the field edge, which is not useful. Too much of a good thing again.

Brock

Thanks Brock

Do you recall if the Minox internal focus Porros are on par with the SE in regard to the correct balance of AMD and pincushion.

Frank, can you also weigh in on this ?

One more while I'm at it Frank. Since they are in the same general price range, do you think the SE has been eclipsed by the Prime HD ?

Bruce

A flat view is very nice, but not necessary for a great image. My ultravid hd 7x42 has a very nice image, razor sharp in the center, wonderful color and a depth of field so big you could almost pull off the focuser. The 8.5 SV has a shallower depth and obviously sharper edges and a flatter image. In terms of center sharpness, they are both pretty impressive.

Bruce,

I would like to comment on it but, sadly, cannot. It has been a good 7 months since I had the Opticron version and quite a bit longer since I had either the Minox or the Cascade. The only thing I remember about edge performance is that there was some field curvature but it was minimal and only a small percentage of the field of view (which it should be considering the narrowness of it).

As for your last question....I am not going to grab that carrot.

If I had the two side by side right now then maybe I could do some comparisons. I don't own the SE anymore. I had three of the 8x32s and sold the last one because I was just as satisfied with the Sightron at less than half the cost.

Maybe one of the folks that ordered the Prime HD and owns the SE 8x32 could chime in when the time comes. For what it is worth the Prime is never going to provide the 3D effect of the SE but it does offer a wider field of view with a larger exit pupil. Those are the obvious optical advantages to it. I would be interested in hearing comparisons on issues such as contrast, apparent brightness and color representation. I think the issue of apparent sharpness is pretty much a wash since both binoculars provide all the detail the human eye is capable of seeing. The sweet spot comparison should prove interesting though.

On another note, I did find the timing of this thread interesting....with the Prime HDs just now starting to get out to the public. The question will be asked at some point....what separates the Euro/Japanese alphas from it?

As has been mentioned in the past I think the last barrier it needs to overcome is that of quality control. Fit and finish on the pre-production unit is excellent. It has "that feel" to it that speaks of quality minus a little work that needs to be done on the eyecups.

Now lets see if the overall quality control level is improved from previous offerings.

henry link said:

"Flat Field" needs at be better defined here.

If by "flat" you mean a field without field curvature that means that objects at the field edge and at the center are in focus simultaneously. It has nothing to do with the rectilinear distortions (pincushion, barrel). Those bend lines toward the field edge, but don't affect the focus of the lines. Angular magnification distortion compresses objects at the field edge (even when lines are perfectly straight) but also doesn't affect focus.

The "globe effect" or "rolling ball" is a subjective psycho-visual phenomenon associated with panning an optic that has angular magnification distortion. AMD is minimized by applying enough pincushion distortion to restore compressed objects to something closer to their undistorted shapes. Individuals differ as to how much pincushion is needed or if it's needed at all.

Click to expand...

Hi Henry,

I completely concur that the two monochromatic aberrations, (1) field curvature and (2) distortion, seem to be utterly confused when people refer to "flat field" optics. It should be associated with reduced field curvature, which as you mentioned results in objects at the edge and center being in focus simultaneously. I image that the confusion is because "flat" usually means unbent, which in this case should be applied to the Petzval surface associated with field curvature, not distortion. http://www.telescope-optics.net/curvature.htm

Referencing Hoger's development of the globe effect, and its reliance on Hemholtz's checkerboard illusion, though, I'm a bit puzzled about where AMD came into the picture as an explanatory variable. He has always maintained that the eye has an inherent barrel distortion (at a perceptual level) that needs to be overcome by the optics. I'm really curious. http://www.holgermerlitz.de/globe/distortion.html

Ed

Thanks again Frank

Bruce

elkcub said:

Hi Henry,

I completely concur that the two monochromatic aberrations, (1) field curvature and (2) distortion, seem to be utterly confused when people refer to "flat field" optics. It should be associated with reduced field curvature, which as you mentioned results in objects at the edge and center being in focus simultaneously. I image that the confusion is because "flat" usually means unbent, which in this case should be applied to the Petzval surface associated with field curvature, not distortion. http://www.telescope-optics.net/curvature.htm

Referencing Hoger's development of the globe effect, and its reliance on Hemholtz's checkerboard illusion, though, I'm a bit puzzled about where AMD came into the picture as an explanatory variable. He has always maintained that the eye has an inherent barrel distortion (at a perceptual level) that needs to be overcome by the optics. I'm really curious. http://www.holgermerlitz.de/globe/distortion.html

Ed

Click to expand...

Hi Ed,

This is such a vexing subject that it seems to be hard to say anything that's completely correct. However, it appears to me that if only enough pincushion distortion is applied to "correct" eyesight barrel distortion that would result in the perception of lines as straight, as in K=1. More pincushion is needed because, even if lines appear perfectly straight, the AMD at K=1 distorts shapes toward the field edge in a way that makes them appear to move toward or away from the viewer as if they were on a turning cylinder set in motion by panning.

This link is the best discussion of the relationship between AMD and rectilinear distortion I've seen. I wish it said more about the globe effect specifically, but I think the implications are clear.

http://www.cloudynights.com/ubbarch...ge/0/view/collapsed/sb/5/o/all/fpart/all/vc/1

Henry

This is certainly interesting discussion, thanks to Henry and Ed for their input, but answering that one seems akin to entering a greased pig contest. This seems a completely objective and totally user defined topic. What I find as "alpha view" somebody else might not. However, flat fields are relatively recent and there were alphas long before the flat field use showed up. So I think the answer to the originally posed question is a simple "no".

Henry,

If your original thought was to explain the globe effect as put forward by Holger Merlitz, I would have to say it's inaccurate; motion percepts contributed by AMD are not addressed. Each individual's need for optical distortion presumably counterbalances intrinsic visual barrel distortion, and that alone eliminates the rolling ball response. His theory is simply mute with regard to object compression and related perspective effects. Of course, one can disagree with his theory, but that's something else.

With regard to the CN discussion, and your interpretation of it, I'm really at a loss to understand how pincushion distortion can "restore compressed objects closer to their undistorted shapes." The math transformation completely escapes me. I also think that calling spatial compression a form of distortion is unnecessarily confusing. But then they do that on CN.

The "globe effect" or "rolling ball" is a subjective psycho-visual phenomenon associated with panning an optic that has angular magnification distortion. AMD is minimized by applying enough pincushion distortion to restore compressed objects to something closer to their undistorted shapes. Individuals differ as to how much pincushion is needed or if it's needed at all.

Click to expand...

Ed

elkcub said:

With regard to the CN discussion, and your interpretation of it, I'm really at a loss to understand how pincushion distortion can "restore compressed objects closer to their undistorted shapes." The math transformation completely escapes me. I also think that calling spatial compression a form of distortion is unnecessarily confusing. But then they do that on CN.

Click to expand...

Ed,

Try looking at the photos in this thread:

http://www.birdforum.net/showthread.php?t=161309

They show the effect of AMD on a circular object as it nears the field edge in four binoculars with different amounts of pincushion. The Swarovski shows the most AMD and the least pincushion. The Zeiss has about the right amount of pincushion to maintain a nearly circular shape and the Leica applies so much pincushion that reverse AMD begins to appear. Eyepieces with very large amounts of pincushion, like Naglers, also have very large amounts of reverse AMD.

As you can see, the short lines near the edge of the Swarovskii field are essentially straight, but its AMD distorts the shape of the circle in a way that mimics the appearance of a foreshortened circular object as it would appear if it were turning around the edge of a cylinder or a globe at the globe’s equator. The effect of AMD on a square shape at that same 3:00 position would be to change it to a rectangle with short horizontal sides, once again mimicking the foreshortened appearance of a square as it rotates around the edge of a cylinder or globe. If enough pincushion were then applied to that shape, its lines would curve but the sides would be restored to equal length.

I realize that Holger doesn’t mention AMD specifically, but both AMD and barrel distortion have in common the same compression effect on shapes near the edge of the field. I believe (perhaps Holger would disagree) that AMD is sufficient to explain why panning may suffer from a globe effect, not only when there is no visible barrel distortion, but even in cases where visible pincushion is too weak to fully correct the AMD.

Henry

henry link said:

Ed,

Try looking at the photos in this thread:

http://www.birdforum.net/showthread.php?t=161309

They show the effect of AMD on a circular object as it nears the field edge in four binoculars with different amounts of pincushion. The Swarovski shows the most AMD and the least pincushion. The Zeiss has about the right amount of pincushion to maintain a nearly circular shape and the Leica applies so much pincushion that reverse AMD begins to appear. Eyepieces with very large amounts of pincushion, like Naglers, also have very large amounts of reverse AMD.

As you can see, the short lines near the edge of the Swarovskii field are essentially straight, but its AMD distorts the shape of the circle in a way that mimics the appearance of a foreshortened circular object as it would appear if it were turning around the edge of a cylinder or a globe at the globe’s equator. The effect of AMD on a square shape at that same 3:00 position would be to change it to a rectangle with short horizontal sides, once again mimicking the foreshortened appearance of a square as it rotates around the edge of a cylinder or globe. If enough pincushion were then applied to that shape, its lines would curve but the sides would be restored to equal length.

I realize that Holger doesn’t mention AMD specifically, but both AMD and barrel distortion have in common the same compression effect on shapes near the edge of the field. I believe (perhaps Holger would disagree) that AMD is sufficient to explain why panning may suffer from a globe effect, not only when there is no visible barrel distortion, but even in cases where visible pincushion is too weak to fully correct the AMD.

Henry

Click to expand...

Henry,

Yes, do I remember your earlier photos, and Ron's. Although I didn't choose to enter the discussion back then, my thoughts were that no behavioral evidence was presented to connect AMD to the induced motion illusion referred to as the "globe effect." As interesting as it may be, therefore, it's premature at best to assert on a factual basis that AMD is the key intervening variable that explains the illusion. If rectilinear distortion and angular compression are reciprocally related, which they appear to be, they also can't be manipulated independently in a behavioral experiment. Essentially, one of the two variables is redundant; one can never tell whether the presence of one or the absence of the other accounts for the results.

Be that as it may, I'm not the one to speak for Holger, although I would be most interested to know what he thinks specifically about your explanation of the illusion.

Ed