AVS Forum banner

Status
Not open for further replies.
1 - 14 of 14 Posts

·
Registered
Joined
·
274 Posts
Discussion Starter #1
I'm in the process of deciding between an XGA and WXGA projector and did some math to determine how much of the native resolution of each format was used by various aspect ratios. I thought the results might be interesting to some of you, as I haven't seen a complete list compiled to date.


(Values are rounded to whole numbers)


Source: 1.33:1

XGA: 1024x768. 786,432 pixels. 100% panel usage

WXGA: 1024x768. 786,432 pixels. 75% panel usage.


Source: 1.78:1

XGA: 1024x575. 588,800 pixels. 75% panel usage.

WXGA: 1366x768. 1,049,088 pixels. 100% panel usage.


Source: 1.85:1

XGA: 1024x554. 567,296 pixels. 72% panel usage.

WXGA: 1366x738. 1,008,108 pixels. 96% panel usage.


Source: 2.35:1

XGA: 1024x436. 446,646 pixels. 57% panel usage.

WXGA: 1366x581. 793,646 pixels. 76% panel usage.

Summary

What this means to me:

On average (assuming 25/25/25/25 viewing time) an XGA projector uses about 76% of it's pixels, and the WXGA uses about 87%. WXGA has the edge here.


Also, picture quality (for purposes of the discussion) is based on the number of pixels actually used, not percent. The WXGA panels use MORE pixels for EVERY aspect ratio EXCEPT 1.33:1. For 1.33:1, it uses the same as the XGA.


So what it comes down to for me, XGA and WXGA are equal performers at 1.33:1, but the WXGA has a higher resolution at anything WIDER than 1.33:1... theoretically, if anything narrower than 4:3 was commonplace, the XGA would provide higher resolutions at the narrower resolutions. Since all sources I know of fall in the range of 1:33:1 - 2.35:1, my logical choice has to be the WXGA panel.


CYA statements:

This of course doesn't take into account the quality of components, lenses, LCD/DLP panels, or light engines, nor does it account for cost. All I'm saying is that all other things equal, the WXGA provides a higher RESOLUTION than XGA for everything but 1.33:1, for which it provides an equal resolution.

Anyone want to argue? (Nicely, please...)
 

·
Registered
Joined
·
1,538 Posts
I think you have just discovered what many of already know. 16:9 IS your best option ( if possible ). The loss of 4:3 pixels is not that much of a crime due to the average LOR for 4:3 materal ( either cable, OTA, VCR, or SAT ) is very small comparedt to the LOR of 16:9 DVD or HD materal.


16:9 materal or higher can really start to take advantage of those extra pixels. This is even more true if you are pumping HD materal into the projector.


LOR = Lines of resolution


Cheers
 

·
Registered
Joined
·
4,129 Posts
...and, given an anamorphic lens and a projector capable of full-panel stretching, you get 100% panel utilization on 2.35:1!
 

·
Registered
Joined
·
2,099 Posts
16:9 panels are advantageous, but not quite advantaeous as this analysis show. You only get real resolution if the source provides it. Since DVD provides 480 lines of resolution, XGA upscales this to 575 lines and WXGA upscales to 768 lines. The WXGA isn't displaying any more information in that case, but it does have a less visible pixel structure. It is only when you get to 720p or 1080i when you get a real resolution advantage.
 

·
Registered
Joined
·
4,223 Posts
I think MR. Faroudja would have to disagree!!!


I understand where you are coming from, BUT I would have to agree with MR. Faroudja. Video processors (triplers, quad) will never be as clear as 720P or 1080i, but they do increase the apparant resolution beyond DVD, through video processing methods that I don't understand, but MR. Faroudja does.

A good WXGA projector or 8" CRT has the ability to take advantage of such processing.


William
 

·
Registered
Joined
·
704 Posts
what about horizontal vs. vertical resolution? The major benefit is the WXGA is the increased horizontal pixel count (esp. if you add a lens), but vertical resolution is *more important* ?


I don't really know the real reason, but is it something along the lines that horizontal resolution is based on bandwidth but vertical resolution represents actual scan lines?


anyone with an understanding of the above please help this very lacking post of mine...
 

·
Registered
Joined
·
388 Posts
A couple of other considerations.


The difference in number of pixels Between XGA and WXGA would be smaller if you used XGA + an ISCO II.


If the WXGA was an LCD and the XGA was a DLP or an LCD with MLA, which would look better.


I'll go for good contrast, blacks and colour and then all things being equal look at the apsect ratio and the cost difference between XGA + Lens (which can be used on the next projector) and 16 X 9
 

·
Registered
Joined
·
5,574 Posts
There is another consideration that I would like to mention, and that is the physical dimensions of the wall on which you project.


It is my conjecture that more rooms are limited by the horizontal size than the vertical. Therefore, it may make a lot of sense to use a 4X3 screen, since you might as well use the extra vertical space to some advantage rather than just having it be wallpaper.


Having put a 4X3 screen up, it also follows that a 4X3 projector might be the most appropriate.


Finally, this argues for an anamorpic lens of the general design of the Panamorph (please excuse me for this intrusion!) in that it compresses vertically.


This partly depends on how much 4X3 material you have. I personally watch a lot of old material even though I prefer 235 aspect ratio aesthetically.


I have been pondering whether my next acquisition will be 16X9 or 4X3, and the above argument still seems valid.


Since the marketplace seems to be moving to 16X9, that may be an independent reason to go 16X9, if most of the good HT equipment is 16X9. The DILA's still seem to be 4X3, and they are currently my favorite for my next system, but that can change.


Thoughts on this further "wall dimension" consideration are sorely welcomed.
 

·
Registered
Joined
·
271 Posts
I've extended the above list with a few more common resolutions. You may need to make your browser window wider for my table to look right. Also, my definition of WXGA is a bit different from dloftis'.


XGA: . 1024x768 . (4x3)

WXGA:..1280x720..(16x9)

WXGA+: 1366x768..(16x9)

SXGA:..1280x1024..(4x3 non-square pixels)

SXGA+: 1366x1024..(4x3)


.................. XGA .... WXGA ..... WXGA+ .... SXGA ..... SXGA+

1.33:1
. Resolution .. 1024x768 . 960x720 . 1024x768..1280x1024..1366x1024
. Pixels ....... 786 432 . 691 200 .. 786 432..1 310 720..1 398 784
. Panel usage ..... 100% ..... 75% ...... 75% ..... 100% ..... 100%


1.78:1
. Resolution .. 1024x575..1280x720 . 1366x768 . 1280x768 . 1366x768
. Pixels ....... 588 800 . 921 600..1 049 088 .. 983 040..1 049 088
. Panel usage ...... 75% .... 100% ..... 100% ...... 75% ...... 75%


1.85:1
. Resolution .. 1024x554..1280x692 . 1366x738 . 1280x738 . 1366x738
. Pixels ....... 567 296 . 885 760..1 008 108 .. 944 640..1 008 108
. Panel usage ...... 72% ..... 96% ...... 96% ...... 72% ...... 72%


2.35:1
. Resolution .. 1024x436..1280x545 . 1366x581 . 1280x581 . 1366x581
. Pixels ....... 446 464 . 697 600 .. 793 646 .. 743 680 .. 793 646
. Panel usage ...... 57% ..... 76% ...... 76% ...... 57% ...... 57%
 

·
Registered
Joined
·
271 Posts
My conclusion is that I will get at least 13% (upto 102%) more resolution using SXGA+ rather than WXGA for all picture sources. It will be competitive price-wise too, with some upcoming projectors. Ok, so I'm wasting upto 43% lumen, but with a bright enough projector, it will still be enough.

:)
 

·
Registered
Joined
·
6,225 Posts
The problem with simple numbers is that the figures often mislead you. I won't dispute the above arithmetic, I'll assume the numbers are correct. However, I wish to dispute the conclusion.


Virtually all digital projectors will automaticly engage the built-in internal scaling circuitry when driven by any signal that is not at the EXACT native panel resolution. The internal scaling is typically far less desirable, in terms of quality video imaging, than a more sophisticated external scaler or a HTPC, driving the panel in native resolution or "passthrough" mode.


I'll mention an exception to this which none-the-less does not disprove the assertion, as this is an exception to the general case. The popular 16:9 digital projector from Sony (model VPL-VW10HT) is incapable of being driven at native WXGA resolution, and always engages the internal scaler.


The popular NEC projectors such as the LT-150 and VT-540 can be driven at native XGA panel resolution, as can many "presentation grade" projectors. The combination of the native resolution passthrough capability and a light engine capable of better-than-average video images from the VGA input is what makes these and similar data-grade projectors so popular in our Forum - they definately offer a big bang for the buck. But the real reason that "native passthrough" feature is there is so you can get the clearest possible slide presentation images from the machine, running a PC application such as PowerPoint.


The other ways of engaging the scaler and overiding the "Native" resolution selection on the popular NEC projectors are:


1) Using any aspect ratio other than 4:3, whether you do this with the "Aspect Ratio" button, Serial Port commands, or via menu selection using the remote.

2) Using the "Zoom" feature.

3) Using the "Auto Adjust" feature.

4) Driving the projector via the Component Video, S-Video, or Composite Video inputs. (YES even if you drive Component Video with a progressive 480p DVD signal, it gets scaled to XGA, as does 720p/1080i HDTV.)

5) Driving the projector with any resolution higher than XGA - it will get scaled down to XGA for display. This includes the HDTV modes 720p and 1080i, by the way (because both exceed the XGA horizontal resolution of 1024 pixels).


Most digital projectors work this way - the 16:9 modes you think you have on such projectors are really phony - you CAN NOT drive just the center section of a 4:3 display, you can only scale your 16:9 input to 4:3 native resolution to drive the panel, and sometimes MUTE OFF or darken the unused top and bottom sections.


The key is, you NEVER want to do so, because your objective is never to invoke internal projector scaling. Instead, you are almost always better off driving an inexpensive projector with native panel resolution and native panel aspect ratio. So the above discussion and figures, while interesting, are not particularly usefull when attempting to achieve maximum image quality on the real world hardware most of us are using. Nor do they help understand how to do so, because the figures lead you down the wrong paths to understanding how common projectors work.


If it's any comfort, the people writing the press releases for such projectors appear to have even less understanding than the average AVS member of the actual internals of the products they are publicising - which in turn handicaps us further in trying to understand their products.


Your real world choices are actually fewer than you think.


If you want the best possible DVD and HDTV imaging possible from a relatively inexpensive projector, get a PC and drive said projector at native panel resolution using the very high quality scaling engine in a modern PC video board, while doing as much processing as possible in the digital domain, and minimizing the A/D and D/A conversions. This is the nerd solution, but the nerds win when it comes to video quality. Almost as good is driving the same projector with a good external scaler and at the native panel resolution - but this costs somewhat more than a HTPC, and doesn't quite equal the HTPC image quality.


If you want maximum convenience, you can switch all your video sources through an A/V receiver, treating the projector like a TV display. There is no improving on this from a convenience perspective - you don't even need a programmable remote, much less worrying about how to set it up. But the average A/V receiver doesn't have the bandwidth to avoid degrading the image, and every RCA connector in the signal path represents a small impedance mismatch, especially significant with higher frequency progressive component images. I can understand why folks want to do this, and it's the one scenario where the more expensive A/V projector has a place - it will exceed the image quality of the presentation-grade projector when displaying interlaced sources, or HDTV signals, because it may have a built-in scaler made from $50 in components, rather than the $5 circuit of a data-grade projector. This is also the configuration where you can dump a whole pot full of money without equalling the image quality available from a HTPC or quality external scaler and a less expensive projector. (The very high quality A/V receivers that switch HD signals with minimal degradation tend to be audiophile grade gear at 3X or more the price of good quality consumer audio gear.)



Gary
 

·
Registered
Joined
·
4,223 Posts
Gary,


Good point, but there are many HOME THEATER projectors that when fed a 480P signal from a progressive scan DVD player will display are very acceptable picture (Sanyo 60, Sony 10HT and 11HT, Sharp z9000u). Even the inexpensive new Piano does a decent job with 480i. I chose a non CRT projectors because I didn't want to make my home theater experience "complicating". Lets not forget that. With used CRTs dirt cheap, simplicity is the only true advantage of using a digital projector. I might as well learn the ins and outs of CRTs if I am going to have to learn about HTPC to get my digital projector to run properly.


William
 

·
Registered
Joined
·
6,225 Posts
Oddly enough, William, the CRT projectors are true analog displays capable of displaying a decent picture from a variety of video modes and resulting scan rates. In this regard they are easier to interface to and frequently display fewer scaling artifacts - because they can often display each video mode in it's native resolution and scan rate. They more resemble multiscanning computer monitors than fixed frequency televisions or even HDTV displays (which display two or three of the fixed video modes 480p/720p/1080i).


The trick to get a CRT projector to really perform at it's best is to find the "sweet spot" where you simultaneously have high resolution, a small beam diameter, no blooming, etc. Often this involves scaling or line doubling/tripling/quadrupling - CRTs also benefit from HTPCs or high quality scalers. (The downside to CRT projectors is you better enjoy tweeking the multitude of analog adjustments - but such adjustments are not required for a digital projector.)


The advantage of a HTPC with an admittedly harder to interface to digital projector is that you typically lock the PC output resolution to the native resolution and scan rate of the projector. Then you use the HTPC to scale the variety of sources - DVD, TV, HDTV, etc. to that exact ideal video mode for that projector.


What makes this solution work best is a combination of three factors:


1) Very high quality video is possible on an inexpensive projector (often because the very same light engine and optics are used as in the 3X to 6X as expensive A/V projector).


2) Minimizing the A/D and D/A conversions by doing as much processing as possible in the digital domain.


3) Using PC video card scaling engines - which exceed in video quality the dedicated video workstations and custom minicomputers used as little as five years back, for movie special effects. This technology matured extremely rapidly due to the frame rate and video quality wars the PC gamers invoked - the current top-of-the-heap ATI and assorted GeForce products are extremely sophisticated - typically more complex circuits than the CPU microprocessors in the PC.


Even Mr. Faroudja's fine products are left in the dust by such PCs. To give him his due, he created the video processor - but his fine designs cannot overcome the handicap of multiple A/D and D/A conversions imposed by packaging his products as A/V components. His digital products come very close by utilizing many of the same circuits found in PC hardware - but still are handicapped by conversions.


The truth of the matter being (evidenced by multiple shootouts in the AVS forum archives) the HTPC always wins - except in limited circumstances where poorly mastered source material causes the PC to misbehave, and the misbehavior is sometimes worse than the video processor misbehavior for such flaws.


The key to avoiding the HTPC complexity is to purchase the HTPC in pre-integrated form, or even purchase the HTPC and projector togather as an integrated set - there are a variety of vendors who would help you, including the forum sponsor AVS. Once you have the configuration optimized, you make a copy of the hard disk configuration on a CD-R or another hard drive - if your configuration gets hosed, you can quickly get back to perfection.


This is definately a niche market - but it's the one that offers the very finest quality Home Theater display possible, and the cost is affordable by most people today - my projector ended up costing less than the HD-capable RPTV I considered buying, and the screen area is four times as great. We also appear to be on the threshold of another leap in video quality by eliminating the few conversions left in our systems, using the new SDI and DVI and Firewire digital interfaces - a little too bleeding edge for me right now, but very promising.


By the way, I share your preference for digital projectors - I had an Advent VideoBeam triple CRT in 1985 - I'll never go back. The worst maintenance task I have now is periodic filter cleaning, a lot easier to live with than triple-CRT focus/convergence/etc.


Gary
 

·
Registered
Joined
·
4,223 Posts
Gary,


I did not realize that you could buy a computer specifically for your individual projector. That would interest me if I knew that I wouldn't have to spend a lot of time keeping it running correctly.

I understand your points and agree, I just am afraid that my computer would crash during a movie, ruining the movie experience.


My other problem is that apparantly the Sony 10HT won't accept a 1366x768 computer signal. Although I think it will accept a 1280x720 (the projector thinks it is 720P HD signal) and upcovert it to 1366x768 (a HTPC no..no..). But apparantly becuase the resolutions are so close the picture quality is still better than 480P from a DVD player.


What are your thoughts? Thanks for the insight


William
 
1 - 14 of 14 Posts
Status
Not open for further replies.
Top