Anamorphic Lenses, VariScope™ and E‐VariScope™ – Which Method Is Right For You?

Jim McGall, Director of Sales, Wolf Cinema October 10, 2014 [Updated 1/20/2020 with 4K source information]

We often field questions about anamorphic imaging methodologies, and especially how Wolf Cinema projectors work best on constant height, 2.35:1/2.40:1 CinemaScope™ screens. We all want to get rid of the top/bottom “black bars” as embedded in our media providers [broadcast, Blu‐ray, DVD, streaming]. Eliminating those unwanted black bars is a great experience for the home theater enthusiast, and we at Wolf Cinema wholeheartedly encourage the sale and installation of CinemaScope ultrawide screens and matching projectors - by whichever methodology you chose to deploy.

There are three ways to do “anamorphic” – (1) using a high‐quality outboard anamorphic lens [Panamorph, Schneider ISCO, Xeit etc], (2) using the on-board lens focus/zoom memory system called VariScope™ [included in select models within the TXF, SDC and REF series], and (3) E‐VariScope™, a technology feature built into our outboard ProScaler video processors.

Below is information from one of my training presentations to help further explain these three ‘CinemaScope’ firing methods:

1/ Anamorphic lens. An external lens is mounted in front of the primary optics. An advantage here is the use of the complete chip set, providing appx. 20% more net peak white performance. But, is there more resolution when using an anamorphic lens?

An important point to remember: the 2.35:1 content is ALWAYS presented at 1920 vertical columns x approximately 810 horizontal lines [Ed: 3840 vertical columns by appx. 1620 horizontal lines with 4K content]. This is a result of the ‘Scope material ALWAYS being provided within the 16/9 delivery image frame. As an example, when using an outboard cylindrical anamorphic lens the image must first be "stretched" [i.e., scaled/processed in the vertical direction]. The top/bottom black bars fall off the chip set. That is a key advantage here – no black bars and no possible dark image “halo” above/below the screen when watching content. However, there is the added cost and complexity to consider in such installations with external lenses.

Some have referred to this method as providing for increased resolution [“you’re using the full chip set, right?”], which is an erroneous assumption – the content resolution STARTED AT, and ALWAYS REMAINS at 1920 x 810 [with 4K sources, 3840 x 1620 - the remaining lines being the ‘black bars’], and as such the end resolution presented on-screen can never be greater than that. The remapping of that content to the full chip set can be brighter, but can also result in processing artifacts: time base errors, aliasing errors, increased dithering and/or mosquito noise, barrel or pincushining distortion… all as a result of the external lens plus stretching the original image. It is difficult, if not impossible, to get back to “pixel for pixel” performance. But this is a very popular method and one we fully endorse: most, if not all Wolf Cinema projectors and processors will support various external anamorphic lens assemblies.

Ex: Using a cylindrical anamorphic lens, the image is first stretched vertically:

From there, the anamorphic lens is deployed [in either fixed or on the moving sled] and restores the geometry:

2/ VariScope™ “lens memories” or lens indexing. Here, the image is simply “zoomed out” so that the 2.35:1 content properly fills the full screen width; correspondingly the image is “zoomed in or down” to reduce the taller 16/9 content, in order to best fit the constant height screen. Pixels get slightly larger when watching ‘Scope content, slightly smaller when returning to 16/9.

Note that those “black bars” above/below the 2.35 content are still being fired above/below the screen. Use care in wall treatments behind the screen, and managed correctly one will not see those ~7.5 IRE black bars. Some feel this is the “purist” solution, in that there never is any video processing or scaling involved – just slightly different pixel sizes.

Minimal scaling artifacts are the end result here. Three possible drawbacks here: one, a slight reduction in peak white output; two, the “time” it takes [upwards of 30 seconds] to zoom in or out, and similarly to return to one of the pre‐set memories; three, there is some image drift possible when zooming in and out, so the desired image may not fall exactly on-screen as originally preset.

3/ E‐VariScope™, or Electronic VariScope. We position the projector at its native optical throw distance so that you are filling the maximum width of the 2.35:1/2.40:1 screen. Somewhat similar to our zoom/lens memory method above (#2), we begin with the black bars “overshooting” the top and bottom of the screen. The inner 2.35 content remains visible on screen.

Then the ProScaler electronically remaps [reduces in resolution] ALL other SMALLER WIDTH AND TALLER aspect ratio images, to fit the constant height CinemaScope screen. The original black bars are still active and “live”, but we are using excellent image processing to reduce all the other taller/less wide aspect ratios. You end up with a 16/9 image in the approximate resolution of 1440 x 810 lines, [2880 x 1620 with 4K content].

Importantly, the pixel size remains the same and when viewed from atypical theater seating positions, the human visual system typically cannot discern any noticeable differences in image quality. The benefits here that it is “free” in our projection systems that come with an outboard ProScaler, or available in a ProScaler add‐on. All 2.35:1 ‘Scope content is seen in its native, purist form. All 16/9, 1.85, 2.20 images etc are electronically remapped to fit and still provide for great imaging fidelity. A further benefit is that the aspect ratio switching is instantaneous, without any noticeable delay in shifting from one shape to another.

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One of the drawbacks to #2 and #3 include the possibility of slight “haloing” or “dark gray image” flare above and below the screen… since the black bars are still being presented. For many clients that is a more than acceptable tradeoff, since these solutions are often readily availble via lens indexing, or provided with a ProScaler when no external anamorphic lens is in use. To solve this the custom installer should treat the walls above/below the screen appropriately with dark absorptive fabric and/or paint. Also a dark blue light cast from a rear LED light kit - a bias light, commonly delivered from select screen manufacturers - can serve to mitigate any dark halo effects from the top/bottom black bars.