elkcub
Silicon Valley, California
I'm going to have to express a contrarian view to what I'm reading here on the subject of "field flatteners".
Can we agree that the ideal situation is for light to arrive at the eye through a binocular exactly as it would have done with no binocular in front of the eye, except of course for the change in magnification? Astigmatism and field curvature simply don't exist in the natural light that falls on the eye, so how would adding them to a binocular image make it appear more natural? It's only when those aberrations are eliminated that we see a faithful analogue to the image space as if it were being viewed through a hollow tube.
I can only believe that the completely inoffensive result of correcting field curvature and astigmatism is being falsely conflated with a pattern of low pincushion and high angular magnification distortions that viewers may find unnatural. Unfortunately, some of the best known binoculars with field flatteners, like the Swaro SV and Zeiss SF just happen to coincidently have those kinds of distortions, but the distortions themselves have nothing to do with the field flattening function. That can be accomplished with any combination of distortions the designer chooses to use.
Henry
Hi Henry,
Distortion is an optical aberration, correct? Shouldn't it also be eliminated since it "...doesn't exist in the natural light that falls on the eye..."? But, as we know manufacturer's deliberately include it in their binocular designs. What's the difference?
The human eye uses field curvature to project visual images onto spherical focal planes. A binocular aided eye must do the same. Field curvature is useful and your eyes know all about it. Violating that natural arrangement has perceptual consequences, just like distortion.
I guess it's a matter of perspective.
Ed
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