Hold your horses guys... or the bickering is going to get this resourceful thread shut down....A little history on 'Constant Area'...1982-1990
A young movie buff Bjoern intuitively utilized the concept of having 'favorite seating rows' for scope (2.35:1) and academy flat (1.85:1) movies as a teenager 25 years ago...1990
Almost 20 years ago, in the early laserdisc days i build my first HT screen. In an outlandish move, i build it in an academy flat ratio (1.85:1) when most of the few people into projection at the time had TV-centric 4:3 screens, yikes.1995
Being dissatisfied with the fact that scope movies had less impact on my 1.85:1 screen due to reduced height, i build my first scope screen (2.35:1). Note that i did not use the term Constant Height at the time, although it was the concept motivating me. Along with all the arguments for CIH presented here. That was 14 years ago, mind you
Satisfaction with the scope screen lasted only 2 years... Not because of the limited amount of scope material on laserdisc, but because i changed my seating scenario from a single to two rows.
Huh? Let me explain:
In the movie theater, i was able to adjust seating distance to achieve the proper size sensation for any aspect ratio material...
With the scope screen at home, the only way to achieve the same 'size' satisfaction with both ratios, i had to move my seat back and forth. Having only one non-fixed seating row and bit of open space to the front, it was a little awkward yet reasonably practical to watch scope material at the actual seating row distance and move a bit forward for academy material...
When i installed a second row to increase seating capacity, the concept of adjusting seating distance via moving any of the seats became impractical. Since the seating rows where fixed now, the only viable option was to 'choose the row' like in the movie theater... Yet, this did not solve the problem.1997Note: This is a key moment in videophile history
I wondered... Why was 'choosing the appropriate row' intuitively feasible in the movie theater, but failed at home? Answer: Different 'seating distance granularity' between two adjacent rows!
I realized that it is the 'size' of the projected image that drives my satisfaction. Neither the width nor the height. To achieve the goal of having the same 'size' for scope (2.35:1) and academy (1.85:1) movies, i had to sit 12,7% closer for academy material.
Assuming a seating row distance of about 4', an theoretical referential row has to be about 35,5' away so that an adjacent row exists directly in front of it which is 12,7% closer. Applying common viewing cone preferences, this implies a 35,5' wide scope screen in a movie theater (distance factor 1.0 x width), a 29,5' wide scope screen in a HD home theater (distance factor 1.2 x width) and a 25,5' wide scope screen in a SD home theater (distance factor 1.4 x width).
Again: It needs a scope screen of that width to be able to accomplish the same 'size sensation' for academy flat (1.85:1) material in the same bounderies (read: with the same height) of the scope screen, by sitting a single adjacent row closer to the screen. Puh, that's a mouth full.
In movie theaters, screens are often much wider, so granularity is even finer than that. In common theaters my favorite spots for the two ratios is usually 2-3 rows apart.
In home theaters on the other side, a screen that huge is utopical even by 20k+ forum means. Assuming a large 14' wide scope screen with two rows at 16' and 12', the front row delivers an image 33% wider than the back row. A far shot from the desired 12,7%.
The consequence is this:
- Either you watch both scope and academy movies in the 16' back row, making academy movies and 16x9 sport 'too small'.
- Or you switch to the front row for academy movies, which makes them waaaay too big, relatively speaking. Actually, moving up to the front row for academy movies will lead to a perceptional bigger 1.85:1 image than even a standard 16x9 screen delivers.
I realized that image 'ratio' and 'size' are two completely seperate concerns...Funny sidenote: Being a software architect, there are basically only three things i am paid for. Abstracting any problem to the n-th degree. Solving them at this highest or any more reasonable lower abstraction level. And keeping things apart that don't belong together (seperation of concerns).
I set out to revolutionize the image delivery concept, being neither limited by constraints a movie theater has to deal with (plenty of width available, height is limited), nor limited by constraints a home theater is plagued with (limited seating row flexibility).
Define three orthogonal concerns of an image.A) 'Relative' image size
There are two driving forces behind this concern. In image too small lacks 'imapct'. An image too big lacks resolution and thus 'quality'. Note that i use the term 'relative' image size here, meaning the size of the image relative to the viewing distance. A 100' wide screen does look puny from 10 miles away...B) 'Absolute' image size
While A is important, the human perception is driven by a second 'size aspect'. The larger the image is in absolute terms, the more authority it induces on us. If A would be the only size aspect influencing our perception... a movie watched on an iPod from 4" away would WOW us as much as a huge theater with 1000 seats and a 150' wide screen from 150' away. We all know this is not the case. The larger the more WOW, as easy as that.C) Aspect ratio
Movies do have different aspect ratios. Check. The sole driving force behind the DP choosing these ratios is and should be framing, thus 'artistic intend'. All other supposed 'reasons' (impact, size, vista, peripheral vision etc) bleed over to the completely unrelated concern A.
The key observation now is, that Concern A is orthogonal from Concern C. Thus, images of different aspect ratios can and will be perceived as having the same 'relative image size'. In reality, image size sensation seems to be driven by area, not width alone, or height.Desires:
- You want to be able to choose the relative image size so that 'impact' is to your liking, independant of aspect ratio (Concern C). And so that 'quality' doesn't suffer for your level of source material. This is acomplished through relative image size (Concern A).
- At the same time you want a screen as large as possible to achieve satisfaction through absolute image size (Concern B).Constraints:
- Due to the 'corse seating distance granularity' issue, switching rows for different aspect ratios is not feasible...
- Due to practicability in most cases, moving seats front and back is not an option either...Solution:
- Don't adjust seating to vary relative image size (Concern A) for different aspect ratios. Stay in your reference seat and vary the image size.
- Keep the image 'area' constant to keep the relative image size the same.
I coined the term Constant Area Screen
to describe the methodology. I coined the term Constant Height Screen
to seperate the methodology that i had for 2 years from the one i just invented.
The result revolutionized movie watching.... for me!Conclusion:
I abandoned my Constant Height screen due to dissatisfaction almost 12 years ago. Ever since i only operated Constant Area screens in my theaters. There is no going back. I inspired many people all over the world to do the same. I stopped 'preaching' CA in home theater communities almost 4 years ago. Over the last 2 years, i notice an increased momentum.... thanks to people like Jeff.
Great! Anyone is welcome to join. This will be the 'last' screen methodology you ever switch to. Don't be shy!