CurtPalme.com Home Theater Forum

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

You cant converge a digital, even if you give it 3 lenses. The pixel structure is a fixed grid.

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

You can if you do it through a processor. The Geo Tahoe can do both converge and align. It would sell like hot cakes for the digital guys (and CRT guys) if someone made a stand alone box. I guess Beun didn't want to do it. Kal, do you know of anyone that would want to give it a go?

CasetheCorvetteman · Joined: 09 Nov 2008 Posts: 6326 Location: Australia

How does it move the pixels to align them?

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

https://www.curtpalme.com/forum_archived/viewtopic.php@t=23068.html

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Doing a blend -- which is what the planetariums (planetaria?) do -- requires excellent black levels, else the black areas of one projector wash out the neighboring projector. That's especially an issue with a signal-processing unit that warps the image onto the pixel grid. The resulting image will not be rectangular, meaning you'll have lots of "black" (gray) areas around the border of the image. I suspect those rectangular gray areas would kill the idea of a digital planetarium blend unless your digital had superb blacks.

I wonder how hard it would be to design custom lenses to do the image-warping optically? With current lens-design software and custom fabrication techniques it might be practical. The optics don't have to be photo-perfect for this application, just "good." But it's probably too fussy and there'd be no way to do any on-site corrections. CRTs are really the best tool for this job.

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

That may be true for planetariums, but you can blend with digitals. VDC had a digital blend with four LED pjs last year.

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Did they actually *blend*, or did they just project the images immediately adjacent to each other?

Spanky Ham · Joined: 22 Mar 2006 Posts: 5643 Location: Comedy Central

It was a blend and I couldn't make out the blend zone.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

With Digitals it is easier to blend due to no roll off in brightness at the edges unlike a CRT . it is the roll off that makes blending a challenge with CRT.

Athanasios

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Hm. OK Nash, you're much more an expert at it than I! Smile

Though I am surprised the any current less-than-obscenely-expensive digital has good enough blacks to do it well.

**Curt Palme** · Posted: Tue Jun 14, 2011 6:12 pm Post subject:

I could be wrong, but they may have manipulated the image via the software, both with geometry and contrast modulation.

NO question that going digital is an issue, the amateur astronomers do notice and apparently bitch like hell about the non perfect blacks. Or so OMSI in Portland tells me, who is still using six 1209s maintained by me.

draganm · Joined: 08 Mar 2006 Posts: 8990 Location: Colorado

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I was at Infocomm in Orlando, FL just yesterday. I saw quite a few large displays that obviously were blended setups, with as many as five projectors in the blend.

Every setup was essentially flawless. Blend zones were NOT visible even when you looked very carefully for them.

Blending is a mature art now.

I saw some great stuff, but the honest truth is that there was not a single display there of any kind that matches a top notch, properly
aligned and calibrated CRT projector for pure picture quality. Many of them are awesome displays but every display had some flaw or other that a great CRT setup lacks. Whether it's pixelization, exaggerated jaggies due to the fixed pixel structure, imperfect blacks, or
other flaws that are harder to define but you know them when you see them, nothing there was really able to equal CRT for its smooth
film-like quality combined with full HD resolution capacity.

The industry may have stopped making CRTs, but that doesn't mean that they've surpassed them in every way that matters.

CJ

**Curt Palme** · Posted: Thu Jun 16, 2011 7:12 pm Post subject:

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

Yow. So 4x a year they have to cough up $7200 for bulbs. On top off the $300k it took to buy the projectors. What a deal. *choke*

**Curt Palme** · Posted: Thu Jun 16, 2011 9:14 pm Post subject:

NOt forgetting that the whole computer system needs to get changed out because the digitals can't control geometry on the curved dome, so everything needs to be replaced. $1 to 1.5 mil is what I heard.

stefuel · Posted: Thu Jun 16, 2011 10:23 pm Post subject:

Only a few here and there care about that little bit of smooth that (only the best) crt will provide. Most have come to the conclusion that digital IS the way of the world and that's the way it is. I come across many high end homes in my travels and I have not seen a late model CRT in any of them. Most middle of the road HT's have JVC and Sony digitals. All the really high end theaters I see now have big honkin Runco digitals. They might not be better but that's what they want.
Hey, I like CRt but I'm done with it. I need a new hobby like perhaps running for Congress and posting nude pictures of my self. That's never been done Rolling Eyes

bbfarmht · Posted: Thu Jun 16, 2011 10:33 pm Post subject:

I'm not done with crt. But I am taking on a new hobby. Always wanted to try model airplanes.

stefuel · Posted: Thu Jun 16, 2011 10:42 pm Post subject:

"Always wanted to try model airplanes."

Been there, done that...