Barco 808s highest resolution/sharpest image

xcj

Standard Member
Hi everyone,

I'v been lurking reguraly here but never needed to post since i seem to find all the information i need on the current threads or searching trough the old ones.

I have a Barco Graphics 808s (port 5)->moome external transcoder->10m HDMI cable->VP30<-various sources.

I before the VP30 i had the Lumagen Vision DVI which i had running @800P(don't remember the refresh rate) and later before switching to the VP30 i had it running [email protected], it converted whatever sources at whatever refresh rates to 72hz.

The VP30 works differently, it applies one treatment to PAL(50Hz) another to NTSC(60Hz) and that reflects on the output, so i calibrated [email protected] for PAL, and [email protected] for NTSC (in NTSC different refresh rates from the input screwed the frame rate of games).

I always thought that 1080i was the way to go in the 808 since it was the biggest resolution i could use since i can't go to 1080P and also i always though that an interlaced picture on a CRT display would look good, since there are is no de-interlacing going on as on fixed pannel displays, it would just sync to it.

A few days ago i have heard, that a lower progressive resolution would look sharper, AND that i don't have to send only 16:9 resolutions. All the resolutions i previously tried were all calculated based on the aspect ratio (Vertical resolutionx1.78=Horizontal resolution).

These were news to me, because i always thought that i could synch to a higher resolution i would have the sharpest image possible, but with the 808 i started playing and i found that lower resolutions look VERY sharp comparing to 1080i, i also found that as long as i adjust the raster size to be 16:9, i dont need to send a 16:9 signal! i can send 1440x960 or something higher on vertical resolution!!

Now my goal is to find the sharpest looking resolution with the highest vertical resolution possible, i plan to use a lot of HD sources and i want to loose the least detail possible and have the sharpest resolution possible on the PJ.

For this i started searching the forum for what others use in the 808 or other 8" machines, and the information was scattered, not everyone agreed, and most importantly everybody was choosing it for DVDs, not HD.

My current setup now is [email protected] (which looks good), and [email protected] (which looks bad, focus and convergence on corners not as good).

Now that HD is here, everyone has either a HD console or a HTPC or a HD-DVD or Blueray, i would think that everyone with an 8" machine would want it running at the highest resolution possible, with the sharpest image possible.

The latest version of what i read here was that people liked 720P or 768P at standard 16:9 resolutions (1366x768 and 1280x720).

Now what are you guys using? Do you constantly try different resolutions? How do you like the sharpness?



Thanks!
 

Alaric

Well-known Member
Hi There,

I also have a BG808s and am interested in this question, although i don't have any HD material or sources....Well save the HTPC but being a Opteron 148 with an ATI x1300 it probably doesn't have the horse power to do 1080 HD anyway !

I have a momitsu which is a highly configurable upscaling DVD player with VGA output which is ideal for CRTs and thats running 720p as a default and its suprisingly nice.

I forget what res the HTPC is curently running as since i've rebuilt it, i've had very little time to play with it...I think its at a 13** 16:9 image, probably at 72hz...I know its higher than 720p.

BTW from reading at AVS/Curts forums I thought a lot of people were saying that while theoreticaly an 8" is too small to fully resolve 1080p and as such would be a bit soft, with some tweaking etc it was actualy posible and looked rather fine ???

Cya,
Lee
 

xcj

Standard Member
I had mine at 1080P vertical resolution, but not at full HD resolution because it wont resolve 1920 horizontaly.I just have to resize the raster to be 16:9 but that also has limits, when you distort it to much from what the signal should look like the problems start. The trick would be to put as big a signal i could send with the least distortion, that is the quest :)

I have been playing with the VP30 vertical e horizontal resolution a lot lately and i still haven't understand the formula, sometimes higher resolution signals look best than lower ones.

Alaric, do you use powerstrip on the HTPC? Does that DVD player let you define the amount of pixels for both vertical and horizontal resolution?
 

Chris Frost

Well-known Member
Talk of pixels can be misleading when dealing with CRTs.

Think of the raster like an artists canvas and the beam spot like a brush. The finer the brush then more lines are possible without them overlapping. The point at which they just start to touch is called the sweet spot. This is the optimum resolution for that particular projector. Any higher resolution will make the image look softer.

The electronic focus and astigmatic adjustments are how you tweak the beam spot size. You are looking for a beam spot as small and round as possible, then as evenly focussed L to R and T to B as possible. When you have this then you can start pushing the resolution up with the VP30 resolution settings.

Regards
 

Alaric

Well-known Member
Hi Chris,

You say talking pixels is confusing, that may be so with a dedicated scaler, but i've never used one...Right from the start on my BD800 and an early ati card as the geforce back then couldn't due a proper dual screen output.

What resolution is 16:9 1080p ???

1920 x 1080 @ 60hz ??

I'm not so bothered about the sweetspot, or the image looking 'soft' by what other people judge etc....However i would like to see it on my CRT for myself and make that call, much like XJC...it may be crap but i'd still like to see it !

Ta,
Lee
 

Chris Frost

Well-known Member
Resolutions are, of course, described in pixels, but when folk talk about pixels wrt CRTs it's easy to forget that a CRT is dynamic system. Something as simple as increasing the contrast will have an effect on the beam spot size which can lead to a loss of image detail because of blooming.

1080p is thought of as 1920x1080 pixels in a 16:9 frame area, but I suspect you already knew that :)
 

xcj

Standard Member
Hi have never been happy with focus on all corners, i think i have to adjust sheimpflug on all tubes , adjusting electrical focus gets good results but never perfect on corners.

Astigmatism is something i touched on the first week i got the PJ because i was stupid :suicide: , i am not to confortable with adjusting astigmatism, so i will leave it to be the last adjustment.

On focusing, besides the optical and electric (trough the menus), there is also focusing on the tubes right? This is another thing i will only do when confortable.

Regarding resolutions , i heard that the resolution you feed into it does NOT have to be 16:9 proportion, as long as you adjust the size of the raster to be 16:9.

Yesterday i had it set up for 1366x1080P, it was watchable, not soft, but also not sharp as it should be; in the OSD of the VP-30 the menu letters didn't look perfect, but i have to fix focusing on all corners first.

I also confirmed that contrast to high produces blooming, reducing it makes the image look more focused/sharp.
 

Chris Frost

Well-known Member
Hi xcj,

If I were you I would think seriously about getting all the focusing issues sorted out first before you converge. That means lens focus, electronic focus, lens flapping, astigmatic and any dynamic focus adjustments if your projectors has them. Tackling these issues after converging will make a lot of extra work for you.

Minor convergence errors that look OK with a fat beam spot will become more pronounced as the beam spot becomes smaller and more defined. (see the attached picture). You will have to reconverge all the memory banks again.

Regards
 

Attachments

xcj

Standard Member
Finaly nailed lens flapping , took a bit to get it right. Redone optical focus and electronic focus.

Astigmatism will try with a dot hatch pattern, i'll take not of the position of the magnets first.

Dynamic focus? How is this done? This is using the focus yoke on the tube itself? Didn't touch it yet.

Thanx for the help.
 

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