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Articles Table of Contents   Page 1: Overview Page 2: Optical Performance Page 3: Apochromatic Behavior Page 4: Hot Spot Issue Page 5: Examples in Color Page 6: Examples in Infrared Page 7: Examples in Ultraviolet Page 8: Lens Designer Notes Page 9: Spectral Transmission Page 10: Conclusions

Apochromatic Behavior

This page discusses apochromatic performance and how it influences the “look” of images.

The “APO” designation of some lenses is a marketing claim of dubious technical merit, generally a nonsense claim compared to the Coastal Optics 60/4.

The Coastal 60/4 offers the real deal. The magenta/green color fringing seen with conventional lenses is completely eliminated with the Coastal 60/4. Does this matter? Absolutely—the effect of the Coastal 60/4 on real pictures is an uncanny clarity, a lifelike rendition you just won’t find in conventional lenses, lenses that tinge the background with funky discolorations never seen in real life. These discolorations are especially troublesome on scenes that include out-of-focus highlights, where the oddball color fringes draw attention to themselves.

Depth of field

In addition to the discoloration caused by non-APO performance, the achievable depth of field seems to be higher with the Coastal 60/4 eg at the same aperture the Coastal 60/4 offers superior depth of field. This might be due in part to the demosaicing process required for today’s digital sensors, since detail over the spectrum is blurred to a different extent by non-APO lenses—hence the color fringes.

Comparison with Nikon 60mm f/2.8D

The comparison below is with the Nikon 60mm f/2.8D, a well-corrected lens of excellent optical quality. Even so, the magenta/green color fringes of the Nikon 60mm are clearly evident, in stark contrast to the completely neutral rendition of the Coastal 60/4 APO.