Originally Posted by JeffNebraska
The projector central calculator says I will get 13fL. Thoughts on whether that's adequate?
Looks like I currently have 23fL. That's a scary difference.
Will I have to adjust brightness (and/or contrast) every time I switch to my anapmorhic lens? Do I just not have the light to make this work?
Contrast and brightness are simply picture adjustments that actually adjust white level and black level, respectively. They do nothing to increase light output. Light output is simply a matter of how much light is created by the projector lamp and then passed through the projector optics. There are also picture modes that allow more light output (usually called things like "bright room" or "vivid"), but those modes generally are wildly inaccurate when it comes to color accuracy, gamma and other picture parameters.
Keep in mind too that most of the brightness calculators use the manufacturer's maximum rated light output, which is not a very reliable figure. Usually that figure is taken when the projector is in "torch mode," with the picture adjusted like how I mentioned above. IIRC, the RS1 in one of its more accurate picture modes puts out about 400 lumens, so you might want to use that for your calculations.
Keep in mind too that "bright enough" is partially a personal call. Here's a quick way to determine if the image will be bright enough for you:
Load up a letterboxed Blu-ray.
Zoom the image in on your projector so that the image within the letterbox bars fills the height of the screen (the sides of the image will fall onto the wall on either side of the screen)
Watch the movie for a good 30 minutes or so, concentrating on how bright the image is and if you find it adequate enough (try to ignore the extra picture information falling onto the wall)
If you are satisfied with that brightness, you should be satisfied with the brightness of the 2.35:1 image (HogPilot's answer about aspect ratios was dead on, btw). As a bonus, if you use a good quality anamorphic lens your actual 2.35:1 image will be about 20 - 30% brighter than what you get with the method described above (since anamorphic lens systems take advantage of all of the projectors pixels being lit up vs. the method above only using 75% of the projector's pixels).