16:9 or 16:10 native projector in 4:3 mode

[Nicola87]

Let's suppose we have a native 16:9 (1280x720) or 16:10(1280x800) DLP projector that is 4:3 compatible. How is 4:3 aspect ratio achieved? Cutting of some pixels or with a sort of scaling with loss in image sharpness?

[cybereality]

I think you can do both. You can usually set this on the projector itself or also on the PC with video card drivers. It depends which will have better quality, but any time you feed a display a non-native signal, expect to have some quality loss.

[Fredz]

What do you want to know exactly ? How 4:3 does work on 16:9 projectors or how to get the best possible quality from a 16:9 projector in 4:3 ?

If the latter, I think the answer is anamorphic prisms. Generally they are used to horizontally expand or vertically compress a 16:9 image for viewing 2.35:1 movies in home cinemas, but they could also be used to convert 16:9 to 4:3.

The resolution would be preserved (with non-square pixels though) and the brightness would be enhanced when compressing instead of expanding the image.

You may have a look here for more information : http://www.zuggsoft.com/theater/prism.htm

[Nicola87]

Sorry, i'll try to make it more clear...

I want to know how a native 16:9 (or 16:10) DLP projector achieves the 4:3 aspect ratio or vice versa.
If there's no pixel deformation (as with anamorphic prisms) and the "projected resolution" has to be the native one (mining that if you give the projector a different input it will convert somehow the input to his native resolution before it's projected) how is it possible to achieve a different aspect ratio??

Thank you all

[cybereality]

Well, you have a few options. First you can letterbox (or pillarbox) the image, which gives you black bars. Or you could stretch the image to fix the screen, but at the cost of messing up the aspect ratio. Some projectors may even have a fill mode which, for example, could make a 16:9 image full screen on a 4:3 display by cropping the sides. Depending on the configuration you may have some, or all, of these options. But, in any case, if you supply a non-native signal to a modern display it is going to look sub-optimal (unless if certain cases: like giving a 1080P signal to a 720P display, that could still look OK).

[Nicola87]

So, i guess i'll have to look into the specific manual of the projector...

Thanks...i'll let you know if have more doubts on a specific model

[Nick3DvB]

I think the answer is anamorphic prisms. Generally they are used to horizontally expand or vertically compress a 16:9 image for viewing 2.35:1 movies in home cinemas, but they could also be used to convert 16:9 to 4:3.

The resolution would be preserved (with non-square pixels though) and the brightness would be enhanced when compressing instead of expanding the image.

You may have a look here for more information : http://www.zuggsoft.com/theater/prism.htm

Cool, I might try this (in reverse) with my 4:3 aspect-ratio projector, its ok for games but I loose a lot of resolution scaling a "widescreen" movie into the 4:3 window. I zoom in to fill the screen more but that's not ideal, I just found a much better solution that works a bit like Philips "AmbiLight" TVs, details here:

http://www.mtbs3d.com/phpBB/viewtopic.p ... 825#p86825