Get an exclusive sneak peek into our new project. >>> Click Here
Our native mobile app has a new name: Fora Communities. Learn more.

Understanding CR

1283 Views 39 Replies 10 Participants Last post by Ericglo, Mar 2, 2005

garyfritz

Discussion Starter · Feb 25, 2005

I have an XG852 that throws a pretty good picture. It was badly setup when I got it but I've gotten it to a pretty good state. I've carefully set the G2 levels, I have the BRIGHTNESS set properly according to Avia, I've even gotten a colorimeter and gotten close to the right color temps. So it should be fairly close to "right." But I really haven't seen other CRTs so I don't know if mine looks like it should, or could.

I've noticed that many scenes seemed too dark, especially when there are bright areas in the picture. I thought at first that the XG's gamma was off, resulting in too-low output at intermediate IRE levels. But after checking it and tweaking the grayscale, I find that the gamma is actually a bit low, resulting in somewhat too-HIGH output at intermediate IREs. So that ain't it.

I wondered if this is just the way a CRT, especially a non-LC CRT, works. It handles all-dark scenes fabulously, but not mixed bright/dark. Does a non-LC CRT have a really low CR within a scene like this? I know the on/off CR is very high -- the lowest lows can go very low -- but I think ANSI CR is measured by the light levels found in a black/white checkerboard, right? Which is analagous to when you have bright AND dark areas in one scene. Does a CRT fall down here, or is mine just not set up well?

HoustonHoyaFan posted this in the recent "M8500 vs. Sony HS-51" thread:
Quote:

in My friend's black room the bright scene washout was obvious on the 6PG vs the HS51. In fact some people commented that in mixed bright scenes the 6PG had a haze compared to the HS51.

That sounds like my picture. There's washout on the dark areas in bright scenes.

Oh, one probably-pertinent fact: I'm feeding it with a Momitsu v880N, which may have a low output level. I don't currently have an Extron or other booster, and probably won't have one real soon. Anybody know where (& with what test signal) to measure video input to see if the v880N is delivering a suitable signal to the XG?

So anyway, I'm trying to understand if this is the way a non-LC projector looks, or if I can improve the PQ once I understand how.

Gary

See less See more

Status: Not open for further replies.

1 - 20 of 40 Posts

mcpherv

· #2 · Feb 25, 2005

Gary, this is exactly the effect created by non-lc optics. There is speculation by myself, and one or two others that a glass faceplate with a better, multilayered antireflective coating could help close the gap between LC and non-LC optics, but currently, no one has attempted the replacment, although, in the last couple of pages of this thread:

http://www.avsforum.com/avs-vb/showt...0&pagenumber=1

JarkkoS mentioned that he was going to try the replacement over the next while.

Vic

EDIT: Also, yes, this is an ansi contrast issue - contrast with light and dark portions on screen. Obviously, LC optics still suffer from this to some extent, but not nearly as much, from what I hear, and from what I understand from the 3M paper linked on the first page of the other thread, as do AC.

garyfritz

Discussion Starter · #3 · Feb 25, 2005

So CRTs do best when the scene is all dark -- which is frequent -- but non-LC CRTs don't look good when there are dark and light areas in the same scene -- which is also frequent.

Something else occurred to me: the lenses on this pj were terribly dusty. I blew them off but I haven't actually cleaned them or the CRT faceplates. I suspect that would help my CR quite a bit.

But it still seems like the darker areas are darker than they should be. I don't know if I have something misadjusted or what.

mcpherv

· #4 · Feb 25, 2005

Yes, the dust will scatter light as well, and reduce the ansi contrast, at least according to the 3M paper as well (well, its been a while since I looked at it, but I'm pretty certain it alludes to that in the contrast section), and it would stand to reason.

I don't know about the adjustments on the XG, so I can't really comment on that one, unfortunately. Someone else will, I'm sure though.

Vic

techman707

· #5 · Feb 25, 2005

Now you done it, Darin will be around anytime now. You said the "magic" word....CR, that'll bring Darin faster than maggots to a dead body.

Ericglo

· #6 · Feb 26, 2005

This is one of the reasons why I honored Darin with the Darin Ratio.

It is the former on/off CR, which briefly became Dynamic Range. Then it became Illumination Ratio(which I liked as well as Darin), but it didn't catch on. So, to end all confusion between ANSI and on/off, I came up with the Darin Ratio in place of on/off CR. Some members seem to like this one the best. Darin is now immortalized because of his contributions to the forum in particular and home theater in general.

Ericglo

techman707

· #7 · Feb 26, 2005

No argument there, DARIN IS THE "CR" MAN.

Don Rombach

· #8 · Feb 26, 2005

Also consider that the better light absorption in the room there is, the better the ratio will be.

The ambient light created in the room by bright portions of an image usually have more effect than non lc lens IMHO

I know that this is not what Gary is specifically inquiring about, but for others with interest in this area, one should not underestimate the improvement to CR with a better light absorption environment.

Chuchuf

· #9 · Feb 26, 2005

The screen can also have an effect on this. If the screen material is translicent at all and allows some of the bright light that is projecting on it through it, and there is a bright colored wall behind it, light can reflect off the wall bouncing back on to the screen potentially lighting up dark areas.

I also agree with Don in that the best single improvement you can make to your HT environment is to make the walls, ceiling, carpet a dark non reflecting color.

Terry

darinp2

· #10 · Feb 26, 2005

Quote:

Originally posted by Chuchuf
I also agree with Don in that the best single improvement you can make to your HT environment is to make the walls, ceiling, carpet a dark non reflecting color.

For those who don't mind going to extremes, this stuff is very good. I'm currently covering a "black" carpet with this stuff using carpet tape. I've never found paint that was close to black velvet, so I have that on my walls and ceilings too for the front 2/3rds of the room.

--Darin

Ericglo

· #11 · Feb 26, 2005

How about Cinefoil that Z-Photo found? It looks like it would another alternative.

Gary, what screen are you using? I have seen you in the DIY forum, but I am not sure if you are experimenting or have settled on a screen.

Ericglo

garyfritz

Discussion Starter · #12 · Feb 27, 2005

Ericglo, I've still got my basic BO screen, which is probably a bit less than 1.0 gain. I want to get up to at least 1.3 or so. The MississippiMud formula supposedly has a gain around 1.3-1.5. Adding metallic silver can theoretically boost that near 2, but I don't think I want to pay the cost of the gray color that comes along with it. I'll probably either paint the BO with MMud, or maybe order some 1.3 gain Dazian fabric and replace the BO with that.

My room is a dark purple. Not totally light-eating, but it doesn't reflect much.

Ericglo

· #13 · Feb 27, 2005

garyfritz,

It sounds like you have minimized the room problems. You can check for some other room ideas, as well as lens masking at this thread http://www.avsforum.com/avs-vb/showt...hreadid=461259

Taking the room out of the equation, that leaves the screen and the projector. You could maybe change the screen to melamine from HD and see if that helps. It is cheap and you could probably return it after your test.

Ericglo

darinp2

· #14 · Feb 27, 2005

Quote:

Originally posted by Ericglo
How about Cinefoil that Z-Photo found? It looks like it would another alternative.

It looks like that is the same as the Black Wrap I have (different brand though). I layed a piece of it on the black velvet and the Black Wrap looks pretty gray in comparison. I've never found anything that eats light like those little fibers in velvet. A flat surface just can't grab that much.

I don't know much about acoustics, but the Cinefoil/Black Wrap might be better for that. From looking at it I don't see how it would have any advantage over just flat black paint though. It might be good for putting inside CRTs because of heat and things though.

--Darin

Art Sonneborn

· #15 · Feb 27, 2005

So the "Perrigo Ratio" didn't stick ?

Art

darinp2

· #16 · Feb 27, 2005

Quote:

Originally posted by Art Sonneborn
So the "Perrigo Ratio" didn't stick ?

I'm hoping none of it will stick.

I liked the Day/Night Ratio, Sunlight/Cave Ratio or something along those lines if people really want to use something else.

Or how about the "Cop's Flashlight In Your Eyes/Buried Alive Ratio"?

--Darin

See less See more

JimmytheSaint

· #17 · Feb 27, 2005

Gary, in regards to the Momitsu, you are indeed correct in stating that the output is very low in comparison to a scaler. It can be remedied by using an Extron box (190F or 109 etc) that boosts the 0.7 ppv to 0.8 ppv with peaking. This makes a HUGE difference in CR and is well worth the cost of one of these units on fleabay for about max $50.

Ericglo

· #18 · Feb 27, 2005

Quote:

Originally posted by darinp2
I'm hoping none of it will stick.

I liked the Day/Night Ratio, Sunlight/Cave Ratio or something along those lines if people really want to use something else.

Or how about the "Cop's Flashlight In Your Eyes/Buried Alive Ratio"?

--Darin

NEVER!!!! It will always be known as the Darin Ratio.

Everyone had there chance with Illumination Ratio, but the light bulb didn't go on. Maybe we should give one last chance to ILLUMINATION RATIO. If there is enough write in votes, then we could go back to this term.

Ericglo

See less See more

garyfritz

Discussion Starter · #19 · Feb 27, 2005

JimmytheSaint, thanks for the tip. I've heard that an Extron booster would help the Momo. I don't see any 190F's but I do see some 109's very cheap. But I've been thinking an Extron 202 would be a better use of my money -- I could use it to switch between the DVD and a Satellite receiver. (Assuming the Extron will switch component, that's not clear from their website.) The NEC 6010 or 6020 might be a better switcher for me, considering I've got an XG, but I'm not certain if it does the same signal boost as the Extron. Plus it's $100-200 or more.

Semisentient

· #20 · Feb 27, 2005

Quote:

Originally posted by JimmytheSaint
Gary, in regards to the Momitsu, you are indeed correct in stating that the output is very low in comparison to a scaler. It can be remedied by using an Extron box (190F or 109 etc) that boosts the 0.7 ppv to 0.8 ppv with peaking. This makes a HUGE difference in CR and is well worth the cost of one of these units on fleabay for about max $50.

I just tried an Extron 109E with my Momitsu 880DX and my Sony 1292Q. The difference is staggering. I'm pretty sure with the extron and contrast set to minimum it is brighter than contrast at 80 without the extron.

I am truly amazed at the difference.

James

1 - 20 of 40 Posts

Status: Not open for further replies.