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Picture This:
Anamorphic Lenses

Nov 1, 2006 12:00 PM, By Jeff Sauer

Premium viewing for premium theater installations.


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One of the most intriguing trends from the recent CEDIA tradeshow was the re-emergence of anamorphic lenses. No fewer than five companies — Digital Projection, Optoma, Sim2, Runco, and Vidikron — introduced anamorphic lens options for their HD video projectors, and all offered beautifully wide, non-letterbox 2.35:1 movie viewing from native 16:9 projectors. It is that kind of movie theater grandeur from home theater projectors that home theater buffs are craving these days.

Runco’s CineWide projector with AutoScope technology

Anamorphic lenses have been around for a long time, although in the past, they've been used mostly as a way to get native 4:3 projectors to display 16:9 widescreen material without letterbox bars. Mostly, that was back when the projector industry was solidly focused on the business market, and light engines were designed with bright presentation slides in mind more than ideal color and video performance. The new wave of anamorphic lenses is likely to be a better fit for today's requirements, however, since today's projectors are already delivering excellent video quality in HD widescreen resolutions.

But what does an anamorphic lens actually do? It stretches video images horizontally to fill a 2.35:1 screen, but doesn't that ultimately mean degrading the image through interpolation? Furthermore, all five new anamorphic options put a second lens in front of the projector's main lens. Doesn't that reduce brightness and contrast? What's more, none of these anamorphic lenses are inexpensive.

So the question is: Is it worth it?

BIGGER, BETTER, WIDER

Anamorphic lenses do optically stretch images horizontally, thereby filling a wider screen. In the present case, all new anamorphic lenses are designed for 16:9 projectors, enabling them to display a full 2.35:1 image without letterbox bars on the top and bottom of the screen. The big screen part sounds great, but wouldn't stretching the image make it look too wide, with faces and figures too fat? Well, yes, it would if the content weren't already squeezed beforehand.

Anamorphic-capable projectors can show full-resolution 2.35:1 content in two ways. First, an “Anamorphic DVD” is encoded so that native 2.35:1 content is squeezed into a 16:9 frame, thereby making everything in the image appear too tall and too thin, at least if it were displayed with a conventional lens. The anamorphic lens then stretches it back to its original 2.35:1 aspect ratio. The caveat is that anamorphic squeezing is not an officially recognized part of the DVD specification, and Anamorphic DVDs are far less common than traditionally encoded DVDs. Moreover, you will see “anamorphic 16:9” listed on several DVDs, but this means 16:9 squeezed into a 4:3 aspect ratio rather than 2.35:1 squeezed into a 16:9 frame.

Most often, 2.35:1 movies are encoded with the letterbox black bars in the MPEG stream. That means that of the 480 vertical pixel lines (576 in PAL) in a standard-definition DVD, a 2.35:1 movie is only using 75 percent of the available resolution. The black bars take up 12.5 percent of the pixels on both the top and bottom. In order to display that content using an anamorphic lens, a projector (or separate scaler) will need to stretch the content vertically, thereby, again, making the images too tall and thin were they to be played on a traditional display. Then, just as with an Anamorphic DVD, the anamorphic lens can do the optical stretch horizontally to fill out the 2.35:1 screen.

Of course, an Anamorphic DVD starts with higher resolution images because they use more of the DVD's available vertical lines. And simply interpolating a letterbox DVD can't make an image better, just bigger. That is, if a movie was encoded with letterbox bars, it has a vertical resolution of 360 lines and zooming bigger can't add detail. However, it probably won't hurt the picture much either, because projectors are almost always interpolating anyway. For example, for a native 720p projector to play a standard 480-line DVD, it has to scale the image to 720. Scaling from 360 to 720 is actually easier math.

The real benefit to using an anamorphic lens with a projector, therefore, is not to add resolution to the movie, but rather to allow the projector to use more of its available native resolution. When a 1080p projector displays a 2.35:1 letterbox movie with the black bars, it too is using only 75 percent of the projector's available resolution. An anamorphic lens allows the projector to use its full 1080 lines (or 720, etc). And even if the resolution of the content itself is much lower, the projector can produce a better picture on the screen.

BIGGER, BETTER, BRIGHTER

Even with the math in its favor, you'll still find purists who argue that an anamorphic lens, literally a second piece of glass in front of the light, will make the picture softer and reduce both brightness and contrast.

It is true that any time you put anything in front of a path of light, you are going to reduce the light getting through, and thereby reduce brightness and often contrast. However, because an anamorphic lenses allows a projector to open the zoom, given the same focal length, you're actually starting with more light coming out of the projector in the first place. Any reduction in light caused by an anamorphic lens (assuming reasonably good quality) will be less than the added light from the wider zoom lens.

Increased softness is similar, although more dependent on the specific lens, if not more subjective. Every lens does have a resolution limitation, measured in lines on a resolution chart. However, generally speaking, the resolution of a good piece of glass will be far greater than the resolution of the projector, albeit a somewhat different measure of resolution. What's more, the benefit of using more of the projector's native resolution will probably outweigh any potential optical resolution loss.

And none of the new anamorphic lenses recently introduced at CEDIA can be considered cheap. The Runco/Vidikron CineWide anamorphic system, for instance, starts at around $8,000 for the fixed ananmorphic lens and runs up to $12,000 for CineWide with the powered AutoScope mechanism that moves the lens into place when needed and out of the way for watching native 16:9 content.

Sim2 has similar prices for its Home Cinema “Scope” system, while Digital Projection's TheaterScope system is slightly more expensive. Optoma's anamorphic lens for the HD81 has yet to be formally priced, but informal estimates of $4,000 add another 50 percent to the price of the $7,999 projector.

All of those are big increases over the cost of the projector by itself, and whether the added benefit is worth the price is going to be a personal decision. It's certainly not an option that will appeal to the large majority of buyers. But then, premium products never are, and that's what the new anamorphic options are about — delivering a premium viewing experience to premium studio or home theater installations.



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