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Message: <blockquote data-quote="ThoLa" data-source="post: 1301189" data-attributes="member: 50374">you've got to make a distinction between principle basic physics and practical engineering. What you are saying about phase shift applies for other forms of optical abberations as well, for example for the chromatic abberation due to dispersion that you get in ANY TYPE of lens, i.e. also in the porro design. In the real world of technical physics it is sufficient to correct such an abberation for the three principle "colors" for which the three types of colour-sensitive receptor cells of the eye are sensitive. If it is done you'll get what is called an apochromatic correction which is universally regarded as a "colour-perfect" image. The principle holds true for phase correction, etc. How do you know Swarovski is not using extra-low dispersion glass in the Habichts? And what do you mean by high end coatings? According to the brochure these instruments have the same coatings as the roof prism models (except for the prism coatings). Where can we get access to all these company secrets? Curious, T</blockquote>