16x9 screen and Panamorph - why remove the lens? - AVS Forum
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post #1 of 11 Old 05-07-2001, 01:50 PM - Thread Starter
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Chris:

I'm confused by your confusion! http://www.avsforum.com/ubb/smile.gif

It sounds like you understand what has to be done, but you said you were confused. To reiterate - yes, you need to do what you said - have a smaller 4x3 image (1024x768) expanded to 1024x1024 by the projector's scaler, and then have the lens squish it back. This has been discussed in past threads. What I was wondering was why anyone would want to remove the lens if they had a 16x9 screen. It doesn't seem to get you anything, unless you can get the projector to zoom in such that a larger percentage of the panel is located within the 16x9 screen area. Even then, how many 4x3 sources are there that would benefit from more than 768 lines? The only thing I can think of is digital photos. Maybe some games? I'm not much of a gamer, but I thought most games were still 640x480, maybe some higher, but none over 1024x768...

Is your point of confusion where you do the stretch? The answer is that you have the projector do it.

And, yes, I do have Dilard.

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post #2 of 11 Old 05-07-2001, 02:19 PM
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Quote:
<font face="Verdana, Arial" size="2">Even then, how many 4x3 sources are there that would benefit from more than 768 lines?</font>
As Mr. Phreddy suggested, there are many of us in the less noble projector class. I have many, many games that are XGA - and benefit greatly from this resolution (simulators especially). I also have extensive composite and S-video satellite equipment that I do not wish to pump through my PC (for various reasons). Since these lesser projectors also do not typically afford aspect ratio stretching (save for some that handle HD/SD 16:9 to 4:3), then one must accept 768x768 using an external scaler, accept a 16:9 presentation of 1024x768 4:3 image (which can be okay for some games), or move the projector or zoom such that the entire LCD grid is on the screen to retain a correct aspect ratio XGA resolution image.


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post #3 of 11 Old 05-07-2001, 02:23 PM - Thread Starter
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Man:

Point taken. I'll revise my statement to be: "there's no reason to swap out a Panamorph on a D-ILA".

- Dave
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post #4 of 11 Old 05-07-2001, 10:24 PM
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Dave,

I guess my confusion was in how the Pj is supposed to stretch an image coming from a PC, when the AR and Resize functions are not available with a PC input. Scale yes. Resize?? That's where I was confused.

Anyway, back to your topic. I'm of the understanding that to display a 4:3 image properly w/lens on, the 4:3 image would have to be altered FIRST, in the PC(or outboard device)realm, before going into the Pj. So if we don't have a method to do this in the PC realm, THEN you would have to slide the Pannie out of the way to view 4:3 stuff properly, otherwise the image would be squished, or to be more accurate, horizontally compressed.

Chris

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post #5 of 11 Old 05-07-2001, 10:41 PM
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Chris...

You seem to have all the theory right....

Things are slightly different for DILA (and possibly others) that can receive any input and anamorphasise it (so I am led to believe any way)... This means that with such resolution to spare if 1024x768 is outputted by source (PC) and the projector stretches to 1024x1024 the lens will correct back to 1024x768... This means a) pillarboxed 4:3 b) more light output... c) correct res for games (many will only work at 'standard' resolutions) etc... This is really a 2 scaler configuration though and not advisable for critical viewing (I imagine)...

There has been some discussion about how to anamorphasise 'all' windows use but winblows seems to be stuck with square pixels.. reasons where quoted in detail and I forget but basically windows doesn't seem to be able to be tricked into mapping 1024x768 over 1024x1024 for example... Some stuff YxY cant deal with and for this you will need to remove the pannie to avoid distortion

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post #6 of 11 Old 05-08-2001, 07:21 AM
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Hi Phreddy,

Bingo. That is precisely my plan.

Although it would seem that there would *have* to be a way to get the AR correct coming out of an HTPC, in reality, I think that brass ring will always be out of reach. You just can't "YXY" every source.

It's all just theory until the Pannie ships, but my plan is to keep all of my 1360x768 16:9 widescreen sources just the way that they are. They will go to the projector in a widescreen AR.

The projector itself will "anamorphize" all sources, and the lens will correct it again.

This should work for D-ILA, but I'm not sure how other projectors will do this. Somewhere in the chain, there needs to be an "anamorphizer" device.

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post #7 of 11 Old 05-08-2001, 10:21 AM
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The scaler has a bad rap!

It's not great for upscaling (antialiasing) images...adding new content where there is none. However, it seems quite good (amazing at times) at downscaling (HDTV to wide SXGA) or simple stretching.

I agree that ideally, a fancy Radeon card would do all of the heavy lifting and send the projector each and every pixel *exactly* the way that it should be. However, I'll be the first to tell you that I am NOT going to be taking my Panamorph lens on and off (or sliding it) for different sources.

If I can't do it from my Pronto, I'm not thinking about it hard enough! It's amazing how much "work" we do to be lazy.

Anyway, I actually *do* think that the double scaling may be the way to go! The HTPC does the tough upscaling, and the projector does the simple "stretching". This will work for ALL sources (even those coming from satellite, other scalers, etc. and not coming from an HTPC) and will allow your Panamorph to do its job all the time...with no movement.

Can't wait for the Pannie to try it all out...

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post #8 of 11 Old 05-08-2001, 10:31 AM - Thread Starter
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Mark:

I'm not sure if you're agreeing or disaggreeing with me. You're saying that the projector will do "stretching" for ~all~ sources? What about anamorphic sources, coming from an HTPC? Surely you'd just "unlock aspect ratio" in your DVD software, right? No need for the projector to stretch that. Anamorphic DVD's are pre-stretched. If you have the HTPC output "square pixels", for the projector to stretch, you're actually "un-anamorphosizing" it.

Also, for non-anamorphic DVD's, you'd be better off using YxY to tell the DVD software to stretch the image, instead of having the projector do the stretching, wouldn't you?

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post #9 of 11 Old 05-08-2001, 10:39 AM
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To be honest I agree with your reluctance to shift the Pannie's prism's around but I dont have a) a good scaler in my projector or b) enough resolution to spare to get my 4:3 sources so I am definitely going to have to either live with the compression on games etc (and anyone using a 16x9 TV also does this) or shift the prisms...

I am thinking about either making some arrangement with a stepper motor and controlling this via serial or going the whole hog and adding a x10 curtain controller (or the like) to automate from Girder http://www.avsforum.com/ubb/cool.gif

This is the main reason I am dying to find an old Panavision Super Panatar as discussed in the Panatar thread as I have been really thinking about a arrangement of cogs so that many many revolutions (of stepper motor) would in really minor shifts of the last wheel (seconds of a degree) which I would use to hold the final lens at correct angle....

Not only would this give me the ability to have 2.35 compression and YxY the 2.35 image over the 4:3 panel for ultimate resolution light output (on my favorite type of movie !!!) but this would all be controllable via Girder / YxY / X10... We are talking one button press setting a chain of events in motion that allows me to use full panel resolution no matter what the AR of the source !!!! I have read quite a bit about these things in the last few days and found one set of specs (on another type of Panavison variable prism lens) that describes its ability to go from 1.33 (no stretch) through to 2.8 (more than enough !!!)...

I am really keen to play with some variable anamorphic prisms and so far have found 3 online all of which have been sold (usually for low $$) within the last month.. I have already been told that this is not going to work (poor light pass through.. long focal lengths... commonly a diopter on final prism etc ) but I still am prepared to throw away some minor $$ to convince myself by trying...

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post #10 of 11 Old 05-08-2001, 09:46 PM
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Millori,

I am certain that you know more about the DILA's than me and I am only thinking out loud here but....

Isn't it crazy to use two scalers in this kind of setup for HTPC generated DVD viewing ???

I thought that digital domain scaling in the HTPC is a big selling point on HTPC's... Now you are going to use this for one set of scaling and then output the signal and do the process again in the PJ ??? This is not the way I would do this unless the scaler in the DILA is really good....

Certainly for application use / games / anything else but critical viewing... say it ain't so http://www.avsforum.com/ubb/eek.gif

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post #11 of 11 Old 05-08-2001, 09:52 PM - Thread Starter
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PMFJI, but I think we're only talking about using the scaler in the projector for 4x3 sources, which would be non-DVD computer sources (games, mostly), and NTSC TV (if you view that on the projector). Anamorphic DVD's are left untouched by the projector, and non-anamorphic DVD's are scaled in the computer using YxY.

Also, the scaler in the projector may not be all that great, but for simply adding lines to progressive images, it probably wouldn't bee too bad.

- Dave
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