CurtPalme.com Home Theater Forum

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

Here's a dumb question.

Can you get a real widescreen pic, without a blended setup for a crt?

I saw this setup w/ a digi bulb and it was nice having the large immersive picture that a CIH setup offered.

Clarence · Posted: Wed May 07, 2008 3:34 am Post subject:

Yes, you can do CIH with CRT. But IMO, it's easier to do CIW and you get better phosphor use.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Yes, I've seen a few CIH set ups and it is too f*cking awesome! It is the "right" way to see films.

The problem with a CIH set up with CRTs is there is no way to make any kind of anamorphic lens--trust me, I've tried. I've even talked with some of the lens makers about any way this could be done. Of course, brightness would still be an issue.

The problem with CIH and CRTs is that you need to set the CRT up for the max width (the 2.37:1 width). You will then be using a very small portion of the tube face (the whole width but only about half the height). You then have to show 16:9 content with 33% less width. That means a very small square in the middle of the tube. The problem with this is you will have to significantly downscale 1920x1080 HD content to be able to resolve it.

CIW is certainly the easiest. However, you can do a good CIA with a good 8" or a good 9" PJ. I tested it extensively with my Zenith Pro 1200X and it was able to pull it off quite well. Although not quite as cool to some as CIH on a 9.5+' wide screen, it can be cooler than CIW.

In the end, two things really challenge the CRT in a CIH set up:
1) You will not be able to fully resolve aspect ratios less than 2.35:1.
2) It will not be bright enough for the width of screen most people want when doing this.

Speaking of brightness. After playing around a lot, I've been changing my mind on that. A brighter picture is better--much better. Clarence is fond of the screen size rule of thumb: 7" CRT - no wider than 7' screen, 8" - 8', 9" - 9'. After playing around, I disagree with this. If you want a really first class picture, the rule is really closer to: 7" - 70", 8" - 80", 9" - 90".

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

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

nuttall_chris · Posted: Wed May 07, 2008 5:11 pm Post subject:

emdawgz1 · Joined: 14 Mar 2006 Posts: 7949

So what i'm getting is that CIH is not effectively doable with a crt. Except with a blendzilla....

hmmm blendzilla. Rolling Eyes

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

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

nuttall_chris · Posted: Wed May 07, 2008 5:41 pm Post subject:

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

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

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

Right now I'm planning on running my Barco 808 on an 80" Stewart Ultramatte 150 (assuming I can get the screen to work; I still haven't tried to unroll it) so I'm kind of excited to see how it'll look. During testing I was using an 85" wide piece of foam core wrapped with a few layers of white fabric of various types... Surprised

The only thing I'm worried about is that the PJ is directly over the prime seating position, so the screen will be relatively close (granted, FOV is the same, but I'm still not sure how that'll work out...).

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

Yeah, I'm a bit worried about artifacts too. If it looks like ass I'll probably sell the screen and look for something else, but it'd be really nice if it works. Electric rolldown and all that. Cost me a hundred bucks and came with a free Zenith Pro900x. Razz

VideoGrabber · Joined: 09 Apr 2006 Posts: 933 Location: Michigan

An interesting discussion.

Person99 commented:
> The problem with a CIH set up with CRTs is there is no way to make any kind of anamorphic lens... <

That's true.

> The problem with CIH and CRTs is that you need to set the CRT up for the max width (the 2.37:1 width). You will then be using a very small portion of the tube face (the whole width but only about half the height). <

This is also true, Dave, but can be turned into an advantage. Since you're only using half the height, shift the active raster and actually use half the tube face. Then tilt the PJ to compensate (this may exclude those with ceiling-mount PJs with no headroom). Because you're using a smaller portion of the tube, you can also boost the beam-current (higher lumen output), with a somewhat reduced life-span. (Vern always ran his tubes "hot", in a CIH CRT setup, to get enough brightness on his 12' wide! unity-gain screen, but used the center of the tubes.) When wear reaches your tolerance point (perhaps 6k hours, vs. the nominal 10k hour expectation), rotate the tubes 180-deg, and start over with fresh phosphor.

> You then have to show 16:9 content with 33% less width. <

Ah, no, 25% less. Or 75% of the 2.35 AR width. Not 67%. (Perhaps you were thinking that it could be 33% wider, in CIW format.)

> That means a very small square in the middle of the tube. <

(a) it's not THAT small, (b) it's not a square, and (c) don't put it in the middle of the tube.

> The problem with this is you will have to significantly downscale 1920x1080 HD content to be able to resolve it. <

If by "downscale" you mean that a scaler is required, and a loss of rez, I'm not sure why you'd attribute a characteristic of an FPD to our CRTs, which are analog and can display anything? It will "resolve" whatever it is capable of, without any scaling necessary. Scaling is one way to do it (and it's working well for Gary), but you could also just shrink the size (which may require resistor changes to get into the proper range, or play with the porches on an HTPC).

I can hear you thinking, "but, but, I have 1920 pixels wide available in my source material. At 2.35 AR I'm displaying all of them, but at 1.78 I have only 3/4 of the width to display them in. That drops it to 1440. I must be losing out somehow." Let's say your setup is good enough to actually resolve 1920-h on a 10' wide screen (unlikely, but for the sake of discussion). That works out to 16 pixels of detail per horizontal inch, and you marvel at the fantastic picture quality of your 10' wide scope film. Then you switch to 16:9 material, and the width drops to 'only' 90". Rez-wise, nothing has changed. You're still able to resolve 16 pixels/inch, and the PQ is the same as before.

Vertically though, you're now trying to display 1080 lines in the same space as 800 before, so there will be some visual softening as a result of the scan-line overlap. With 1080i display mode, this will be significantly less than you would think (and less than at 1080p). The majority of softening that most folks attribute to line overlap isn't line overlap at all, but rather due to exceeding the system's BW limit, with the high scan-rate leaving nothing left over on the h-axis.

Person99 · Joined: 09 Mar 2006 Posts: 4899 Location: Flower Mound, TX