Televisions.com’s Florian Friedrich was on board the Home Theater Cruise 2009, where he found out about the latest developments in the home-entertainment sector. At one of the talks that Florian attended, video expert Joe Kane explained why anamorphic lenses in digital projection systems actually make the picture look worse, not better.

The problem

On Blu-ray, 2.35:1 movies always have black “letterbox” bars above and below the picture, since the Blu-ray standard defines a 1.78:1-format (16:9) picture. Although this means that 2.35:1 pictures won’t use all of the pixels in the signal, since the organisations responsible for the HDTV standards — such as IBU, SMPTE and EBU — decided that a unified picture standard solved more problems that it created.

But for users with a 21:9-format (2.33:1) projector screen, it’s obviously frustrating to see black bars on all four sides of a picture whose format essentially matches that of their screen. What’s even more irritating is that part of the projection chip’s output is being wasted on black bars. Why, many wonder, can’t we use that lost brightness in the picture instead?

The proposed solution

The answer, so the theory goes, is to stretch the picture vertically to an anamorphic format and then project it through an anamorphic lens. This produces a bigger picture with the same brightness per active screen area.

The video processor carries out the initial, vertical magnification, so that the image fills the projector’s imaging chip. There’s therefore more light — overall — in the projection. The anamorphic lens then stretches the image horizontally to restore the correct geometry.

The net effect is this: The brightness capacity that was previously wasted on the black bars is now all used by the picture (apart from slight losses due to the anamorphic lens). That sounds like a great solution, but as Hollywood video consultant Joe Kane explains, it can do more harm than good.

Why that doesn’t work:
There are two steps to the process, each of which has a picture-quality disadvantage:

Step 1:
Stretching the picture vertically to fill the otherwise black space
This creates the anamorphic signal, but involves awkward up-scaling (ten lines to 13) that causes losses in picture quality. Since this is not a whole-number multiplication, it will unavoidably involve introducing unpleasant scaling artefacts, as well as causing the picture to lose a significant amount of detail. The only way to avoid reducing the picture quality is to use a 4k projector, so that the conversion involves a much larger multiplication.

Step 2:
Stretching the picture horizontally to restore the correct geometry
There are a number of problems here. For one, it involves putting an additional optical component in the beam’s path — which will reduce both the brightness and the contrast.

More generally, the anamorphic lens will make the pixels larger, and larger pixels mean you’ll need to sit further from the screen to enjoy the same picture quality. Joe questions the logic in creating a bigger picture, only to sit further away after all — the image will fill the same field of view as if you just left the letterbox bars in place and sat at the ideal viewing distance.

At the ideal viewing distance, the image will fill the sharpest section of the viewer’s retina — smaller images allow the eyes to be distracted, making it harder for you to lock into the action; larger images mean you’ll have to move your eyes around too much to take in the picture, making viewing less relaxed. If you were already at the ideal viewing distance, therefore, and you haven’t gained any brightness, there was simply no need to make the picture bigger in the first place.

But some home-cinema users insist that the image will end up brighter. This simply isn’t the case; for a start, the chip’s brightness per area — the so-called luminance — doesn’t increase. Of course, using more of the chip’s light output in the same area would give the picture a greater luminance. But that’s not the case here — instead, the higher light output spreads over a larger picture area. The overall effect, therefore, is that the picture gets bigger but stays at the same relative brightness.

So, in the end, these users are introducing artefacts to the picture and gaining no extra brightness, just for the sake of filling the screen. And, as Joe explains, you’ll just have to sit further back from it anyway.

Questions to Joe Kane on the subject of 2.35:1 projections:

Q. Do you see 2.35:1 projectors becoming available in the future?
A. “It’s going to happen a lot faster in LCoS or LCD technology than it will in DLP, but neither one of those technologies can do anywhere near as well in picture quality, so I don’t care. DLP is going to be slow to get there, although we do see 4k coming in DLP.”

Q. What about using a curved screen with the anamorphic approach?
A. “I really like my audio, and using a curved screen is the same as putting a parabola in the room. It’s going to destroy the acoustics, and there’s no way of recovering. I don’t think there’s any equalisation system that’s going to make up for a curved screen — not to mention the geometric distortions. It’s absolutely correct that curved screens were introduced to make up for variability in the lenses, but they’re a fixed solution to a variable problem, and that isn’t the way we should be doing things.”

If you want to join the Home Theater Cruise 2010, you can register at www.hometheatercruise.com. You can also discuss this topic with other enthusiasts at www.avsforum.com.