So I think I'm getting it. W/ out the lens in place, overscan by about 1/2" for 1.85:1 films and w/ the lens in place, adjust the lens placement so it overscans by about an inch?
At the risk of the Pixel Fanatics coming after me... I wouldn't bother adjusting zooms and overscan between lens-in and lens-out.
We're talking a few pixels here. Make one adjustment that'll cover everything and leave it bolted in place.
Overscan so that your main formats - 16:9, 1.85:1, 2.40:1 all fit within the screen's masked area, heightwize.
You'll lose a few pix from the 16:9 stuff, as it spills onto the masking, but any director who claims you have to see EVERY pixel in his frame is
2. A fanatic.
3. A poor director (he makes his audience go to so much trouble because he didn't shoot properly).
All films are meant to be masked to some extent. They're shot with that possibility, nay probability in mind. You can afford to lose a few pixels to get rid of annoying black slivers between the top of your image and the top of your screen.
If you get too bound up with aspect ratios and deterministic set-ups where you try to get everything right (and then find out you forgot something that ruins it all) you WILL go crazy.
Overscan by about 3/4" to 1" top and bottom and you'll find everything fits,and what you lose by it being cropped with masking you won't notice (because you can't see it).
Here's a true story of a deterministic user who was so finicky he outsmarted himself (a recent installation of one of my lenses that I witnessed, mouth agape): the owner of the theater got 6 roller coats of black paint on his walls and roof, plus another 4 sprayed on top of the roller coats. The spray painter used too fine a mist and, as each new coat of sprayed paint went on. Each new coat stuck to the existing coats, eventually forming 'whiskers" made of paint. Nice and matt, nice and black... but you couldn't touch it!
The installers took three days to complete the installation, something that should have taken 4 hours. They couldn't touch anything without deforming the fine "whiskers" of spray paint and leaving a mark. Every day the owner checked for marks. The installers were paranoid. You couldn't even use gloves... gloves left a mark! and they never knew when the owner was going to make a surprise visit for a spot check.
I was there on the last day, supervising the set-up of one of my lenses. All we had to do was put the CineSlide (GetGray's motorized sled) in place. It took 5 hours, with laser levels, trembling hands and much sweat wiped off many brows. We couldn't touch the ceiling until the exact time that the CineSlide was put into place. Everything had to be measured in advance, then double checked. Then triple checked. We couldn't slide the sled around because that would have marked the ceiling.
A difficult client to work for? Too deterministic.Too obsessive about everything being perfect to even accommodate his workers.
After the installation was complete, the carpenter walked in and commented that the owner was going to be upset the first time the dog came in and pooped on the carpet. Someone said, "He'll hit the ROOF!". Quick as a flash the carpenter replied, "THAT'LL leave a mark!". We all agreed we'd like to be there when that happened.
Moral of the story: don't worry about the fine details. Just leave yourself enough room for the inevitable mistakes you're going to make.
(The original, roller painter had walked out on this owner, owed $3,000... he told the owner to keep it. It was worth it to get out of there.)