Q: I have a native 16:9 4K projector and a 2.35:1 cinemascope projection screen; so, do I need an anamorphic lens to view full size 16:9 content on that 2.35 screen?

Yes, if you are going for optimal performance and “no” if your projector has lens memory and you cannot reconcile with the cost of the anamorphic lens. Here is the difference for each.

Projecting onto a 2.35:1 screen (lens zooming): On a native 16:9 4K projector, lens memory is a pre-set feature that allows you to letterbox zoom and fit the 2.35:1 screen’s footprint. To many, this looks good enough. The bad news is that you are losing 25% (over 2,000,000) pixels. They are not gone; they just appear black to give the illusion of no longer being there. Because 25% of your pixels are out of the game and your projector is trying to stretch what is left to fill your screen, you lose 1/3 of your resolution and 25-30% of your brightness depending on the settings you choose.  It is also worth mentioning that when your projector blacks out 25% of your pixels, it absorbs the light energy which manifests itself as excess heat inside of your projector.  Over time, this excess heat will shorten your projector’s operational lifespan. Some projectors have lens memory so you can switch them at the click of a button but should the projector not have this capability, you’d have to perform this manually through your remote.

Projecting onto a 2.35:1 screen (Anamorphic lens):  In order to take full advantage of all of the pixels from your projector (maximize brightness and resolution) you will need an anamorphic lens and avoid the extra light from over spilling beyond the limits of your 2.35 screen. In other words, your projector needs an anamorphic lens to maximize your video performance.  A memory lens horizontally stretches your image while electronically upscaling your 16:9 projector’s vertical resolution. This means you get the 2.35:1 performance without losing brightness or resolution.  Because you are not running black content in letterbox mode for hours on end, this puts less wear and tear on your projector.

Other options, projecting 16:9 content onto a 2.35:1 Screen: You can still project a 16:9 image onto a 2.35 screen but the image will be smaller and you will have empty space on the sides.  No anamorphic lens is needed in this case but you would have to manually adjust for both aspect ratios when viewing 16:9 and 2.35:1 content.