C.I.H. Explained

There is something special about going to a cinema to watch a film in CinemaScope. The curtains open to reveal a wall to wall screen with an image much wider than conventional home video's HDTV 1.78:1 can achieve.

Previously the best we could do at home was to letterbox that "Scope" image, but thanks to modern home theatre [digital] projectors combined with an anamorphic lens, it is now possible to project all images at a Constant Image Height, recreating that DELUXE WIDE SCREEN cinema experience in the home and preserving the true Aspect Ratio the way the director intended.

ENJOY "CINEMASCOPE" AT HOME

When set up correctly, a Constant Image Height system will allow you to switch between different Aspect Ratios. This may be done electronically using a video scaler [either in the projector or an external device] or by removing the lens from the light path for the smaller Aspect Ratios of 1.85:1/1.78:1 [second image] or 1.33:1 [third image]. There is only 4% difference between 1.85:1 and 1.78:1.

2.37:1 FULL SCREEN "SCOPE" IMAGE

The C.I.H. system allows 100% of the projectors panel to display the "Scope" image at the full height of the screen with NO black bars top and bottom. Letter boxing only uses 75% of the vertical resolution for the image. The other 25% is wasted on the black bars.

1.78:1 STANDARD WIDE SCREEN IMAGE

Standard Wide Screen like HDTV [1.78:1] and films with an aspect ratio of 1.85:1 will use the full height of the screen but the width will vary. The smaller image width is still very watchable because we are more sensitive to image height than image width.

1.33:1 IMAGE

Side pillars of unused screen will be seen when displaying smaller Aspect Ratios like the two images [1.78:1 and 1.33:1] above. Side masking may be employed to cover these areas of un-used screen to help create a more cinematic look.

SCALING + OPTICS = CORRECT GEOMETRY.

Constant Image Height is a 2 part process - "Scaling and Optics". Here is how it works.

LETTER BOXED "SCOPE" IMAGE

When a film's Aspect Ratio is "wider" than that of the display, the image height is reduced to fit in the width and still be able to maintain correct geometry. Normal "letter boxed" images [like the one above] waste precious vertical pixels on the black bars seen at the top and bottom of the image. In this shot, the image is actually window boxed as the 16:9 image is being projected onto a "Scope" screen.

ELECTRONICALLY SCALED IMAGE

PART ONE is the scaling or electronic reformatting of the image to use the full panel of the projector. The key to scaling for C.I.H. is to maintain the full width of image, but remove the black bars. As a result, the geomtery is changed, making the image appear "tall and thin" as if "vertically stretched".

Full panel use has the potential to increase both the brightness and vertical resolution of the projected image. This can be done either with the projector [depending on the type of connection and source feed] or with an out board video processor. A 16:9 "enhanced" DVD is actually stored this way on the disc, but a "235" film will still have some black bars top and bottom that need to be removed.

To create this image, I have used "4 x 3 ZOOM" on my projector to totally remove the black bars. Some projectors that do not have mode 1 or 2 scaling will require an external Video Processor.

OPTICALLY STRETCHED IMAGE

PART TWO is the optical stretching of the image to restore the image geometry. The anamorphic lens sits in the light path of the projector and optically stretches the light beam by a factor of 33% (1.33x for video and 2x for film) in the horizontal direction. This takes the 1.78:1 ratio of the 16:9 display and Horizontally Expands it by 1.33:1 resulting in an image with an aspect ratio of 2.37:1. This process therefore restores the geometry of the electronically "scaled" image, resulting in a full height, but now much wider "scope" image.

SUBTITLE POSITIONING & CIH

Subtitles, [whilst not in every film], are often needed for us to understand what is being said [particuarly in a foriegn film] when the spoken language is not our native language like in this scene from the Star Wars Saga. In the first photo, I have "scaled" the image as normal using the 4 x 3 Zoom setting on the projector. However, in this case, the subtitles are not readable due to them being positioned half on the hard encoded black bars that mask this DVD. What is happening here is that by "scaling" the image [used effectively clip off the black bars], I am also clipping off any portion of video information within those bars, and in this case, part of the subtitles.

CLIPPED SUBTITLES

To solve this problem, I used to use the Samsung HD-950 for its "ezview" feature. In this case, the player acts as a video scaler to not only "scale" the image for CIH, but to also to relocate the subtitles well into the active picture area. Since upgrading to Blu-Ray, I discovered that my Samsung BD-P1500 also relocates the subtitles when stored as a bit map.

REPOSITIONED SUBTITLES

In my opinion, video transfers should not be altered from what was seen at the cinema. The subtitles should remain in the active image where they appeared in the cinema release. Theatrically most subtitles will be a single line of text that extends across the width of the screen.

Above: Screen shot of Star Wars: A New Hope when played on a Samsung BD-P1500 Blu-ray Disc player. It seems that most BD players have this feature built in.

PRODUCTS - ANAMORPHIC LENSES & ADAPTORS

THE COMPLETE PACKAGE

The RUNCO CINEWIDE is probably the most expensive CIH solution, but is a total system comprising of everthing you need for CIH in your home including the purpose built DLP projector... If you already have a projector, there are quite a few anamorphic lens products on the market, some costing more than a projector itself. The prices range from just a few hundred to many thousands of dollars. There are basically two types - cylindrical [top image] and prismatic [bottom 3 images].

ISCO III with CineSlide

PRISMASONIC H1200M/H600M/H300M

PANAMORPH UH380

"Aussiemorphic Lens MK3"

The Prismatic lenses also come in two types - Horizontal Expansion and Vertical Compression.

The Adaptor I use is the AUSSIEMORPHIC LENS MK3. It is an affordable prismatic adapter now with CA Correction and it can be used with any native 16:9 projector [TR pending]. When the projector is fed a "scaled" signal from an anamorphically (16:9) enhanced DVD or Scaled Blu-ray Disc and projected through the lens on to a "Scope" screen, it produces a DELUXE WIDE SCREEN presentation with NO black bars top and bottom...

ANAMORPHIC VIDEO TEST PATTERN

When the LENS is properly aligned, the circles of this pattern should all appear "round" and you will have uniform focus from edge to edge. The grid is useful for testing for aberrations such as Chromatic and Grid Distortion caused by the adapters.

Mark

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