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Message: <blockquote data-quote="Bob Blaylock" data-source="post: 501254" data-attributes="member: 16749">I'm not so sure about your first point.  In general, I think most lenses tend to have better quality toward the middle of their image circle; with any aberrations tending to be more prominent out toward the edges.  Using an FX lens on a DX body means you're avoiding the outer edges, where quality is going to tend to drop off more.  Granted, an FX lens is going to be engineered to meet whatever quality specifications are demanded of it; across the entire FX-sized area of its image circle.  A lens that can cover an FX-sized sensor, but whose quality drops off too much toward the edges, could possibly be sold as a DX lens.  In any event, there is no disadvantage to using an FX lens on a DX body, other than that the FX lens might have cost more than a comparable DX lens.  Which sort of leads to your second point, but I think even that point is rather weak.  If the lens that meets your needs happens to be an FX lens, then that's that.  It's still a perfectly-fine lens,even if you only ever use it on a DX body.  You may lament the lack of a cheaper DX version of that lens, but doing so does not detract from the usability of the FX version.  No real disadvantage here, to a DX body.  The DX body can still use the FX lens, just fine.  The DX body offers the potential advantage that a lens manufacturer could offer a cheaper DX version of a lens, but failing to do so does not constitute a disadvantage to the DX body compared to an FX body; only an unrealized potential advantage.  If you're particularly interested in long-focus lenses, then the DX actually has an advantage, inasmuch that the crop factor effectively increases the “reach” of a telephoto lens by that factor.  The same “reach” that you'd get with a 600mm lens on an FX body, a DX body will get with only a 400mm lens.</blockquote>

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