Quote:
Originally Posted by Don Pensack
If the two curves (sagittal and meridional) deviate, that indicates astigmatism. The center of the field is at the bottom and the edge is at the top. The scale is in diopters (the eye can usually accommodate 1, but 2 would be seen as curved).
Ideally, the two curves would not deviate and they would be vertical.
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So by looking at the graphs it would be true to say that;
The 14mm (and perhaps 5mm) have the least astigmatism, even though it has negative field curvature.
The 30 & 40mm have the least field curvature, even though it does have some slight astigmatism.
I'll test this next time I'm out, but I don't know how well I'll go, as it's easier to compare different EP's of the same focal length than different EP's in the same range of different focal length.
Cheers mate :-)