I wanted to post some updated lumens numbers and correct a mistake I made in my original review regarding lens shift.
First, after 422 hours of use, here is my updated lumens chart
As you can see I have lost 20% of the lamp's brightness in the High Brightness iris mode and 35% in all other modes. I can't explain the discrepancy. In my case, the result of this loss of light output has forced me to start using the Bright lamp mode. The Economy lamp mode/Medium Iris mode now returns less than 10 FtL on my 100" 1.3 gain StudioTek screen, but in the Bright lamp mode it is still over 12 FtL.
I made a mistake when discussing the effect of lens shift in my original review. I made 2 assumptions, both of which turned out to be incorrect. I assumed that the 20K would ship with the lens shift at its neutral position as the default AND I assumed that zero lens shift would yield the highest light output.
The result of the first incorrect assumption was that, in my original install with the lens about vertically aligned with the center of the screen, I had to use lens shift to move the image down significantly to fill the screen. This led me to believe that zero lens shift was the lens aligned with the bottom of the screen (shelf mount) or top of the screen (ceiling mount). In fact, zero lens shift is the lens aligned with the center of the screen, exactly the way I had it originally. I was confused about this because the 20K does NOT ship with its lens in the neutral state. Its default is with lens shift invoked for either an inverted ceiling mount (lens aligned with the top of the screen) or a right-side-up shelf mount (lens aligned with the bottom of the screen). Sharp must just assume that these will be the most common installs.
Now, when I moved my shelf mount install down about 15" and noticed measurably higher light output, I attributed this to the fact that I had gotten the PJ closer to the zero lens shift position. I think I even wrote that more improvement was possible if I could only move the PJ lower. As it turns out, this was correct, but for the wrong reason. This leads us to my second mistake.
The best light output for the 20K is NOT zero lens shift. Sharp apparently engineered the optics so that the best light output is just where I originally said it would be: an inverted ceiling mount (lens aligned with the top of the screen) or a right-side-up shelf mount (lens aligned with the bottom of the screen). It's just that the lens shift required to accommodate these installs, though it is the default shift and offers the best performance, it is NOT the zero lens shift position. Zero lens shift (my original install) actually gets you LESS light output. Weird, uh?
I hope that this clears up any confusion my original post may have caused.