The wavy "fun house mirror" effect when you pan left to right seems to be a fact of life that most people accept. My Vortex Viper 10x42s "have a bad case." My Leupold 8x42s (Wind river cascade, if memory serves) have it much less, even though, on balance, they're not quite as nice a binocular. (but the price was right). My Pentax 10x43s (DCF SP) have very little of this effect.
That was what I was expecting from them. In the world of astronomical eyepieces, if you want to get funhouse mirror effects, go try something like a Pan Optic 24mm from televue. But the Pentax XW eyepieces don't have it.
Today I get an email from a person who knows more than I about binoculars and he says that ALL his binoculars have pincushion EXCEPT his Leicas. (He has not tried Pentax) I have been moving around the forums here for a couple of days and I see many aspects of performance discussed but no one seems to mention pin cushion. Seems that it is an accepted fact of life and no one cares that a left right sweep in a Vortex is going to be a rollercoaster.
Anyways, methinks that I like my fields flat. If not perfectly flat, at least flatter than my Vortex, which all in all is a very nice binocular. Really. I'm just saying, it ain't flat. It ain't even close to flat.
But it seems to me from reading these posts that most folks don't care about flat. I never see it come up? I'm too new to bird groups to make much of a generalization but it seems like most of the people who even talk about pincushion are coming from astronomy backgrounds....or do I exaggerate?
thanks
greg n
I think you don't understand why it's added.
It doesn't come up with birders because it's a feature ... adding pincushion (which all binocular makers do as part of the design) reduces the perceived "rolling ball" effect when panning.
Another of those things that differentiates terrestrial binocular use from astro use. Rolling ball effect is very notble in daytime but when panning star fields not so much.
Search the forum for more discussion of the rolling ball or rolling globe effect and why pincushion is added deliberately.
And welcome to the forum ...
Hi Greg,
Sure we care, just some of us care more than others. Holger Merlitz, a well known binophile and math geek to the max, cares perhaps more than anybody else in the whole world as you can see from his very nice paper: http://www.holgermerlitz.de/globe/distortion.html
Even if you don't really dig into the equations, the visual aids and reading explains the situation pretty well.
A more accesible wrapup recently appeared in a discussion here in the Swarovski section. BF optics maven, Henry Link, summed it up in his typical stunningly lucid way, and I hope he won't mind being quoted here, first referring to rolling ball, then to how it can be corrected:
"What you're describing is actually the way a flat field appears to the eye. Imagine that your eye is suspended above a huge flat checker board. The square just below your eye looks nice and undistorted. Now imagine swiveling your gaze toward the edge of the board. The more distant squares will appear increasingly foreshortened and smaller, just as you described. The only way to make those edge squares appear more similar to the central square is to distort the flat checker board into the shape of the interior of a bowl. But then the lines that form the squares will curve. That curvature is pincushion distortion. So, we have to choose our poison: a flat field in which objects appear foreshortened or flattened toward the edge creating a "rolling globe" effect when panning or the bowed lines of pincushion distortion."
It seems odd that your ebuddy claims that Leica does not have pincushion. Of all makers, they are the only ones I know of to acknowledge that they DO put pincushion distortion in to mitigate the rolling globe effect when panning. It works, judging from my 8x42 Trinovid Leica. Zeiss and Swaro do about the same as Leica, by the way, just don't beat the drum about having a "distortion' in their binoculars, dubious marketing strategy one one would think on Leica's part, although honest. In comparison, I have a 7x50 Fujinon porro that gives a great image in many ways, one being a lack of distortion, ie telephone poles at the edge look perfectly straight, a beautiful thing to behold. But try panning, and it is funhouse of a different kind than you describe, but funhouse for sure! Having experienced both, I prefer pincushion.
I agree about the Panoptics, the stars swoop pretty bad as you pan along with those things. I've read that it's a necessary evil in that case, in order to have the stars at the edge appear so sharp. I don't pan my telescopes much, so in my fast Newtonians, Panoptics are the ticket. I have not tried the Pentax eyepieces.
Anyhow, the bottom line is you are obviously annoyed by pincushion, and I sure can't tell you "don't be". You need to find out if you are more, or less, annoyed by a "flat", distortion-free, field. But I promise it isn't perfect either.
You can't have it all, all at once. The best field correction "may" be a very wide field, so you don't notice the edges much anyhow, with enough astigmatism at the edge so it's a bit blurred making you care even less, and a little bit of pincushion, not enough to fully eliminate the rolling globe effect, and not enough that the bending distortion is pronounced, either. I am just totally making this up. Oh, well, if only I was optical director of a binocular company!
Welcome to the forum, and thanks for paying attention to what your binocular is doing.
Ron