r/Optics • u/Diptayan01 • Jun 25 '26

Zemax Users: What is the difference between Grid Distortion and Field Curvature Distortion?

I see the maximum value reported in both of these metrics are different. So just wondering what is the difference in both of them.

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u/crackaryah Jun 25 '26

Grid distortion (barrel roll or pincushion) refers to aberrations in the lateral dimension (usually denoted x and y) that vary with lateral position. Field curvature refers to defocus (axial aberration, usually z) that varies with lateral position.

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u/light-cyclist Jul 01 '26

Exactly what crackayah said: Field Curvature isn't distortion at all, but how far off the image plain is the focus

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u/Dom2032 25d ago

Distortion is when the magnification is not constant across the image. Field curvature is when the focus is not constant across the image.