While your post clearly offered some welcome insight into the dilemmas involved in choosing our system set ups, the more I considered what you wrote, the more I had issue with the by-the-numbers approach it seemed to exemplify. I understand you made a "general" recommendation, and clearly it's an approach used successfully by quite a number of CIH enthusiasts and installers. But I think that it's useful to look at reasons for there being exceptions to such a recommendation as well. So in the spirit of sharing reasons for differing approaches...
Originally Posted by Dennis Erskine
While you can achieve the IMAX aspect ratio, easily, you cannot achieve the IMAX impact or effect, without very high ceilings. On the other hand, most rooms will easily tolerate a wide format screen. My general suggestion is to consider the tallest reasonable 1.78:1 format your room and seating distances will tolerate. Then take that height and calculate screen width for a 2.35 or 2.40 aspect.
So this boils down to saying: If you can't replicate IMAX viewing angles, don't bother trying to give IMAX images more impact at home and just stick with a CIH system.
In the face of what really can be achieved via careful choice of screen size and masking, this seems a tad, well, defeated. And in my experience there is no reason to throw in the towel like that.
On the CIH approach recommended above, an IMAX AR film will have less relative impact than any scope film, and the same relative impact as, say, the 1:85:1 comedy film The 40 Year Old Virgin. Yet CIH devotees will often point out issues with 16:9 screens saying "the Lord Of The Rings should be presented with more visual impact/immersion than The 40 Year Old Virgin
," hence a rational for CIH. By the same reasoning, though, it seems just as unfounded to decide that IMAX AR films, like Avatar, will be given no more visual size impact than a non-IMAX comedy like 40 Year Old Virgin. That seems "wrong" as well.
So...two issues:1. The recommendation to set the CIH screen size by via the choosing as large a 16:9 image as you can get/tolerate.
While that tends to be the CIH mantra, a number of us have found this approach just didn't work. (For us). What I can tolerate in terms of image size varies with source quality and image content. From my seating distance of between 10 and 11 feet I can enjoy certain 16:9 content at
up to around 124" diagonal. But by no means all content. I find that image size overwhelming to watch for all material, and lesser source quality is exacerbated at that size.
And if I chose my scope screen size based on a 124" diagonal 16:9 image I'd have a 143" wide scope image. Given that I find a 124" wide scope image is hitting my comfort level width from my seating distance, a 143" wide image would be way, way to big for my comfort. And I can only imagine how awful lots of lower quality source content (including DVD or not top tier Blu-Ray transfers) would look at that size. No way would I want to be stuck with that image size for scope.
So I found I had different tolerance levels for image size of different ARs and source quality. The base-it-all-on-your-16:9-image just doesn't work for me.
And I'm not alone, which is one reason why Constant Image Area is a matter of discussion, and implementation, among some people.2. Giving up on giving IMAX more impact.
This is were a by-the-numbers approach would have really robbed me of
the benefits I'm now enjoying in my system, IMAX AR films included.
First, you are no doubt aware viewing angles aren't the whole story. Actual changes in image size count. I can put a scope film on my 24" diag iMac screen and move my face closer to the screen to achieve a THX-recommended viewing angle. But that hardly makes the image suddenly appear really big. Rather, my brain just says "I'm closer to a small image." Because obviously our brains use a variety of cues to establish image size, not simply viewing angle.
So given that viewing angles don't tell the whole story about image impact, and we are left to do the best we can in any system, the fact a certain standard viewing angle can't be achieved shouldn't, in of itself, be a reason to abandon giving IMAX films more impact.
If you can make your IMAX image significantly bigger, that's going to increase it's impact.
Now, of course image impact can be very relative. My max 124" wide scope image seems huge to my friends with smaller rooms and smaller screens, while it will seem puny to someone with a much bigger room and scope screen. But within our rooms we are juggling the impact that occurs via relative image sizes. Scope will still have that "wow" feeling if your scope image is wider than your 16:9 image, whatever room size you are dealing with.
And the same principle applies to trying to achieve more impact for IMAX AR films. Even if you can't achieve a pure commercial IMAX viewing angle, if you can make your image significantly taller than your scope image, and significantly bigger than your regular 16:9 image, then you CAN get a gratifying degree of extra "WOW" and immersion for IMAX ARs.
For instance, last night I had a bunch of guests watching the UFC on my screen. We watched it at 16:9 105" diagonal - people were comfortable with that image size and I watch a fair amount of 16:9 content at that size too. These folks have also watched scope movie content on the system at around 122" wide. So that's pretty much a CIH experience. But then I put on some scenes from the Avatar Blu-Ray. I mentioned that since Avatar played at IMAX theaters I was going to expand the screen. I expanded the image size (4-way-masking) up to (if I remember) 124" diagonal. When the Avatar image came on at that size it had a "Holly sh#t" reaction from pretty much everyone (myself included). At a 10 to 11 foot viewing distance, the change in relative image sizes really did engender a similar type of "This is HUGE
" vibe that made it subjectively feel like you've gone from a regular theater to an IMAX theater. My friend said it felt like you could fall into the image...just like it can feel at IMAX. Whether we had achieved actual commercial IMAX viewing angles or not (not), it sure gave an IMAX like impression. A very worthwhile home theater experience, IMO. (And I'd be amazed if anyone viewing the system wouldn't agree).
There is no way that effect could have been achieved if I'd stuck with a CIH size relationship for all content, given that any scope film would always be the same height yet far larger on the system than IMAX content.
It's immensely gratifying to be able to achieve this effect. But I would not have it if I followed a by-the-numbers approach were you set your constant screen height via a 16:9 image size, and if I'd abandoned giving IMAX images more impact simply because I couldn't achieve actual commercial IMAX viewing angles.