My new PJ can zoom. Why would I ever consider an Anamorphic lens?

What do you think of a lens with a 4K projector? Obviously brightness is still a factor, but is the difference between "2160p" significantly better/smoother than "1620p"?

There's no question that with 2K a lens is essential for the finest quality image (provided it's a good lens).

With 4K, I still think it's a good idea. Maybe even more essential.

If you're using a 4K projector then you want the best quality on offer. Add a couple of pluses if you can get a hold of actual, genuine 4K material (as opposed to up-scaled Blu-Ray).

An A-lens preserves the pixel density of 4K much more than zooming it does. There are over 2 million extra pixels with a $k-Anamorphic (Freudian typo: I meant "4K-anamorphic") combination than with zooming a 4K image.

You want to throw out 2 million pixels (equivalent to about an entire Blu-Ray/2K screenfull of pixels)? Then why did you buy a 4K projector?

I do agree with Get Gray, however: with 2K stuff upscaled the need does not seem so pressing, although I have seen a couple of 4Ks in operation and their auto-zoom/focus/offset is awful slow. They have to get that re-focus after zooming and re-positioning PERFECT to preserve the 4K brilliance (and the re-positioning isn't so repeatable, either after a few cycles). With an A-lens, of course, there is no refocus, no re-positioning and the image is up to 20% brighter than zooming.

Summary: use 4K with a lens and the overall picture quality is better preserved than with straight zooming.