Let's start by explaining what it does. It's an automated system that lets you zoom in and out, and focus, and save settings. In addition it digitally moves a widescreen image up or down the screen to make it fit.
From a practical standpoint, this gives you the option, of buying a Cinemascope shaped (2.35:1 or 2.40:1) screen instead of the tradititonal HDTV screen (16:9 which can also be expressed as 1.78:1). Once you have it all set up - assuming you buy that shaped screen, as otherwise, you wouldn't normally need the feature for anything), at the touch of a button you can go from filling the 2.35:1 screen with a movie - no letterbox at top and bottom, to a 16:9 shaped image, with letterboxing on the left and right.
This means, from a "big picture" standpoint, that you'll have a larger picture when viewing widescreen movies than when watching HDTV, including sports.
Captain Pike, from the Star Trek movie. PT-AE7000 first:
It's never that simple, of course. Not all movies are Cinemascope ("anamorphic") shaped. Almost all animation - from Disney, Dreamworks, etc. is 16:9. Almost all of the 3D titles are also not in Cinemascope shape, but 16:9.
In other words, there seems to be a shift towards 16:9, which was the intent, to begin with of creating the 16:9 format as a compromise between 2.35:1 and old style TV 4:3 (1.33:1).
On those other movies, and all your normal digital HDTV content, including sports, you would have a larger image with the standard 16:9 screen.
Now that I've personally switched from my old 128" 16:9 screen to a smaller 124" 2.35:1, I have these thoughts.
1. I like having most movies being larger, and not having letterboxing. Of course, projectors like the Panasonic and the Epson, - these ultra-high contrast projectors, don't light up those areas very much with their dim blacks. So I appreciate the lack of letterboxing less than I would, say, with a typical $1500 projector, with their noticeably inferior black performance.
2. The trade-off is that I'm not pleased with the size of my sports images, nor my 3D in general. My 124" 2.35:1 is only about 98" diagonal when doing all the 16:9 content. (Of my 50 or so pieces of 3D content on disc or DVR, almost all are 16:9, including movies like Tron Legacy, Monster House, Cars 2, etc. My old screen, in terms of surface area was almost 70% larger when I'm watching 16:9. I'm not happy with that large a reduction. Had my room allowed it, I would have gone with at least 140" in 2.35:1 just to have an equivalent of about 110" diagonal.
This created a conundrum for me. (I love that word.) Fortunately, I'm in a position to come up with the ideal solution. I plan to order a 3rd screen for my theater. I've got the Studiotek 130 (the 124" diag 2.35:1), and behind it, a 100" diagonal Silver Screen for passive 3D projectors (I've only reviewed one - the LG, as almost all are active, it's got gain, but it also hot spots, so it's rarely used.
I plan to add a motorized 16:9 screen with a size of at least 118" diagonal. haven't decided which surface yet, but the larger screen is inevitable.
Bottom line on Lens shift: 16:9 is traditional, but a pure movie enthusiast will be very inclined to consider a 2.35:1 screen. If you can't live without this ability to use an anamorphic shaped screen, then the Panasonic is likely the home theater projector for you, in this comparison.
How many people actually go widescreen? I have no good numbers but one company, upon my request - Carada, did provide me their trending on Cinemascope (anamorphic) screens. They really sell primarily (or only) to the home market.
Before I roll out the percentages, let me point out that in addtion to screens, Carada makes their Masquerade (I have one in my testing room), which is a screen masking system. Most of those Masquerades, like mine, work with 2.35:1 or other cinemascope screens. As a result a much larger portion of those shopping for screens would tend to gravitate towards Carada, due to the Masquerade.
Still from the data he prepared for me, mostly those anamorphic screens grew slowly as their percentage of sales, from 2004 - 2008 from 2% to about 6%
Then (and I assume in conjunction with the Masquerade hitting the market), there's a significant jump over the last three years where their percentage has been over 10%, and it looks like about an average between 15 and 16 percent. When I consider the Masquerade and the anamorphic screens sold with it, I'll speculate that the number of Cinemascope width screens is probably at least approaching 10% of the market. Consider, though, that almost all systems with $10,000 plus projectors use Cinemascope screens, and those more expensive projectors could account for half of the anamorphic screens.
Home Cinema 5010 Split Screen
The Epson Home Cinema 5010, can split the screen. You can define one window as an HDMI input, and pretty much use any other input for the other. I've tried both an analog computer input, and a component video input as part of my testing. It works! You can have both images the same size, or one larger than the other.
Unlike some other split screen or PIP (picture in picture) setups, the Epson allows you to use all hi-def sources. Since any projector has only one circuit for HDMI, but typically two jacks (or three), only one input can be HDMI. Actually it would be nice if they provided a second HDMI circuit, but there are plenty of work arounds.
I don't know if you are going to rig up the room so you can watch football while others are watching the Rose Parade, with one group wearing headphones, the others using the speakers (or headphones all around). Maybe split screen can keep the peace between the kids. Or maybe it's just putting my fantasy football real time stats, up there next to the game.
Or how about a movie on one side, a game being played on the other, or a game on one side, and a sport on the other...
It's a cool feature, and all it really needs is for you to have two sources hooked up to your projector, to make it work, as long as they aren't both HDMI (or both component, etc).
Panny Lens Memory vs. Epson Split Screen:
As with Panasonic's Lens Memory, the vast majority of you also don't have need for the Split screen. The thing is simply this. If you really want Split Screen abilities, then it's an Epson for you. If you must have a 2.35:1 or 2.4:1 screen, then the Panny has the advantage.
Now if you are of the 90+% that isn't going to choose a projector based on these two different features, we can move right along, and focus more on performance.