curvature of field

I understand the Nagler and panoptic EP's are better at handling low f/ reflectors, and that they have a lot of curvature of field as a result of their strong saggitta varying where the image ends up for equal length light paths for rays across the mirror.
I also see in Rutten and vanV ( I forget how to spell the man's name) that the first Naglers had significant curvature of field, as quantified by how many diopters of eye accomidation it took to use them.
I've learned one reason the nagler types work well on wide light cones is the negative lens in the first group lessens the steepness of the light cone the following lens need to deal with.
Question: is there anything, besides the barlowing effect, about current naglers, with regard to ability to handle curvature of field, like reverse curvature in the EP balancing out the primary, etc, that explaines their success with low f ratios?
Also, can some one share the equation that describes the negative effect on the image due to curvature of field in low f/'s?
Thanks,
Dan

Dan --

I'm under the impression that the newer Naglers have gone in the other direction: that they've traded off more pincushion for reduced curvature of field.

I, for one, don't notice much curvature on my T6. Then again, my eyes might just be more accomodative than most.

-- Jeff.

Dan, I think maybe you've misunderstood the discussion in Rutten and van Venrooij, although it has been awhile since I read it myself. It has also been some years since I owned a Type 1 Nagler, but I don't remember much curvature to it. There is significant INTERNAL field curvature to the upper half of the eyepiece, but the field group is designed to match it. The resulting eyepiece as a whole has, I think, unremarkable field curvature. Both the Barlow effect and the internal curvature matching could be said to be responsible for the good correction of the eyepiece, but as Nagler will tell you if you ask, the eyepieces were designed as whole systems.

Besides the additional lens surfaces, the deleterious effects of these negative-positive schemes are debatable, but generally I think the internal baffling of the eyepiece becomes that much more challenging, especially if the field group isn't much oversized.
--
Mike