Chromatic aberration of a simple 2-element 450mm f/4.5 lens + G1

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LoneTree1 Senior Member • Posts: 1,539
Chromatic aberration of a simple 2-element 450mm f/4.5 lens + G1

This was  taken though a telescope as described.  What some don't realize about chromatic aberration is that the light from the blue and red ends of the spectrum is defocused across the entire image.  We generally with reasonably-corrected lenses see it as a coloured band at light-dark image interfaces (edges of things) but since the red and blue light is defocused for the entire image, it reduces contrast of the entire image.

More advanced 2 or 3 element lenses (apo) containing ED or fluorite elements almost completely correct it.  Highly-advanced 4-element lenses known as "super-achromats" (Zeiss, for e.g.) correct for 4 colours (not just 3 as in an apo lens) and further reduced chromatic aberration.  However, the only truly colour-free lenses use only mirrors.

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