CinemaScope™ HDHT - Part 3 - Screens and Aspect Ratios

[Rodolfo]

If your HDTV has a fixed frame, such as an LCD/plasma panel or a rear-projection TV, and you want to see the CinemaScope™ image at its intended aspect ratio, there is not much that can be done about the bars at the top and bottom of the screen. As a result, the bars use part of the valuable vertical resolution of the 16:9 TV or the projector's chip. To make things worse some technologies, such as LCD projection, show the black bars as dark gray, distracting the viewing of the actual image.

The HD chip of a front projector is fixed to the resolution of its design (720px1280 or 1080px1920 pixels). Many projectors today are chip-based DLP, LCD, and LCoS technologies at 720p resolution. More recently, several affordable 1080p projectors were introduced to the market.

[url=http://www.hdtvmagazine.com/articles/2007/06/cinemascope_hdh_2.php]Read the Full Article[/url]

[dabhome]

It is a very cool idea to get fixed height no matter what aspect ratio you are using. Since you are forced to live with content which is in 1920x1080 format in order to get a 2.35 aspect ratio you need to use a scaler to scale only the portion you want and to produce non-square pixels. Although the 1920 stays the same, you have to take the portion of the image that is not in black bars and scale it up to 1080 lines. This warps the image and thus requires an anamorphic lens to display it correctly.

However, if I am displaying a 16x9 image there is no warping of the image and therefore I do not want the anamorphic lens.

For a 4x3 image, I could put black bars in, but it would be better to warp in reverse and have a inverse-anamorphic lens. I don't know if one of those exists or if it is worth it.

What you have not described in your system is how you go about adjusting your system for the different aspect ratios. How do you change the lens? How do you change the warping of the scaler? What do you do when the aspect ration is only 1.85 or something else?

It would be nice to get details about how your system eventually was set up.

You have also not pointed out that it is extremely important to have a great scaler. Remember, regardless of using the full potential of the projector you are still only getting a portion of the 1920x1080 signal to work with. This is very similiar to taking 480p content and displaying it on an HDTV.

[Rodolfo]

dabhome,

Your first two paragraphs describe what the articles already say; I do not take them as questions.

The answer to your third paragraph: the sled supporting the lens removes the anamorphic lens in front of the path of the projector to view any non-2.35:1 content, showing that content with side pillars obviously. The anamorphic lens is a separate piece; it is not to replace the projector lens.

Your 4:3 question is responded above, there no need for inverse lens. There is no need for any lens on non 2.35:1 content.

1.85:1 aspect ratio content will show with very thin top/bottom black bars on 16:9 AR viewing, or you can apply a very small overscan to make those bars go away.

There are lens that perform the switching of formats within the same lens structure, they do not use a sled to transport those lens in/out, but they are always in the path of the projected image, even in 16:9 and 4:3 content.

I personally do not want ANY lens in front unless I need them, so a sled is money well spent when it comes from my pocket. Some people use no transport and move the lens manually in/out, some people save on the sled and have the lens always in front.

Regarding the details of the system I implemented, two articles before this one provide the names of the manufacturers of the HW. The next articles on this series will go a bit deeper about the pieces, although I am not planning to make this series a technical review of components, when reviews are available I will provide some links.

Regarding my choices, there are many products in the market that can be used for an equivalent purpose, from projectors, scalers, lenses, screens, etc.

Regarding the importance of the scaler, I mentioned several times in the articles how important is the overall quality of the scaler and the lens for a quality result. Many projectors already include a scaler but a $3k to $5K quality scaler could not possibly be within the enclosure of a $3K projector.

Regarding your comparison of 480p displayed on a HDTV, which you said is similar to the scaling of CinemaScope

[dabhome]

Thanks for the reply. You are correct, the first two paragraphs were not questions. I was trying to sum up what you said as a precursor to my question. Sorry for the confusion.

You are also correct that it is a huge difference between scaling 480i to 1080p then the 2:35 aspect ratio. I was only pointing out that a good scaler makes a difference. Besides, only a good scaler will allow you to have the type of control necessary for the scaling required in the first place.

I reread your articles and I now see from your picture in Article 1 and some other statements that you indicated that you were using a sled to move the lens. Sorry, I missed it the first go around.

All and all I have really enjoyed the articles.

[aaronstout]

While I understand the desire and theory to display constant height material, it seems all this effort could be avoided and a much better image obtained if they would just make front projectors with the 2.35 native aspect ratio imaging chips.

Scaling any fixed pixel display is going to soften the image somewhat. I understand gaining image brightness and vertical resolution with the current solutions, but a native imager chip would seem to be a much "cleaner" and overall cheaper solution.

Rodolfo, you work around these manufacturers all the time... do you know of any plans to offer projectors with a 2.35 native aspect ratio? I realize that for narrower images some of the pixels would be "wasted", but this would be IMO a much better solution. For DLP we would be at the mercy of TI to offer that imager, but for others, it seems they have control of their display chips and could tool up for this, if they wanted to.

AaronS

[akirby]

Broadcast HDTV will be much more prevalent from a consumer standpoint than 2.35 movies and HDTV is 16:9. I can't see the mfrs making both ratios.

[Rodolfo]

I agree with akirby, the domain format is were the investment goes to, 16:9.

aaron,

I have not heard of any effort toward 2.35:1 chips on any technology, DLP, LCoS, LCD, etc for the purpose you describe, I must admit that I never went deeper to get more information about the subject, but I will certainly do.

The premium of having a chip with more pixels on both sides to maintain 1080 vertically and match the 2.35:1 aspect ratio would only be put to work on 2.35:1 content for a market of people that is reduced, for now.

I do not see that happening at consumer prices.

Best Regards,

Rodolfo La Maestra

[Richard]

aaronstout,

There is another purist way to implement 2.35 without a lens and scaler, using the zoom of your front projector. This can't really be covered here due to the length required to explain all this and I have an article in our publishing corral waiting...

I can tell you this, the zoom 2.35 method is not for everybody and not all projectors have the features to do it. Rodolfo is concentrating on the automated plug and play version for 2.35 since most of our readers fall into that category. The zoom method is for the hands on videophile only who knows how to drive his system.

[7617]

I personally am using the zoom lens method to achieve constant height projection. I am using a Panasonic 900 projector firing on a 96" 16x9 screen that I have masked down to a 2.4:1 aspect ratio.

I then use the zoom lens (along with the vertical lens adjustment) to keep the image the same height, whether it is 1.33:1, 1.78:1, 1,85:1, 2.35:1, or 2.4.1.

I am very pleased with the result.

[Richard]

If the 900 has vertical centering you'll find that far easier than the tilt...