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SYC
Joined: 16 May 2006
Posts: 269
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| Posted: Wed Dec 17, 2008 9:48 pm Post subject: What is the dymanic contrast of CRT? |
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Does it mean the same thing as the "peak white" character of CRT? How does it work? What is its function? Can someone give me some examples?
Thanks.
SYC
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benareeno
Joined: 22 Mar 2006
Posts: 1614
Location: ottawa, canada
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| Posted: Wed Dec 17, 2008 9:58 pm Post subject: |
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Isn't dynamic contrast a digital projector gimmick??
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ecrabb
Forum Moderator
Joined: 13 Mar 2006
Posts: 15909
Location: Utah
TV/Projector: JVC RS40, Epson 5010
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| Posted: Wed Dec 17, 2008 10:05 pm Post subject: |
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"Dynamic contrast" usually just refers to on/off contrast. That's as opposed to ANSI or in-scene contrast.
SC
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Wed Dec 17, 2008 11:13 pm Post subject: |
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It is on/off as SC mentioned. However, in the digital world they divide on/off into two categories. "dynamic" is the CR achievable with a dynamic iris whereas "native" is what the panel/light engine of the PJ can do all by itself.
So whereas the JVC RS2 has a native on/off CR of almost 30,000:1, the Panasonic AE3000 has a "dynamic" contrast ratio of over 50,000:1. However the Panny's native CR is going to be much lower than that, probably around 5,000:1.
On most content, you cannot tell the difference, but there are a few scenes which you can. So, the Panny will have a bigger range between an all black and an all white screen than the RS2 will, but with a very small bright white object on a black field, the RS2 will have either a brighter white dot, a darker black, or both when compared to the Panny.
EDIT: much of the Panny stuff was for comparison only. The Panny properly calibrated will actually only do about 14,000:1 dynamic (so it is always worse that the RS2). I was using "advertised numbers" for comparison purposes.
One other thing I should add is ANSI CR. High ANSI CR has been the domain of the DLP and still is. Good DLPs tend to range in ANSI CR from 650:1 all the way up to 1000:1 (compared with a 9" LC CRT of about 150:1). LCoS and LCD are far behind this (which is one of the reasons the RS20 looks so "CRT-like"--it has great native on/off CR but relatively poor ANSI CR). ANSI CR really gives bright images "pop" and makes them look very 3 dimensional. LCD has been horrid with ANSI CR, but Panasonic have pulled off something of a miracle with the AE3000 and got its ANSI CR up to 450:1.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Thu Dec 18, 2008 1:03 am Post subject: |
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SYC is asking about Cathode Current Limiting I think.
Last edited by Mark_A_W on Thu Dec 18, 2008 2:18 am; edited 1 time in total
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Dec 18, 2008 1:30 am Post subject: |
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OK, let's take Mark's point. OP, what exactly are you asking and why?
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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WanMan
Joined: 19 Mar 2006
Posts: 10270
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| Posted: Thu Dec 18, 2008 11:11 am Post subject: |
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What's the meaning of life?
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Trust no one. Absolutely no one. Advice of the board.
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Z-Photo
Joined: 07 Mar 2006
Posts: 2749
Location: Huntsville - Alabama
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| Posted: Thu Dec 18, 2008 3:10 pm Post subject: |
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42
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The Only GOOD AMPRO - is a Dead AMPRO.
wait - are they not all DEAD already?
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Thu Dec 18, 2008 3:49 pm Post subject: |
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....Well, it's nothing
special. Try and be nice to people, avoid eating fat, read a
good book every now and then, get some walking in and try and
live together in peace and harmony with people of all creeds
and nations.
~Month Python
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jask
Joined: 17 Mar 2006
Posts: 10187
Location: kamloops BC
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| Posted: Thu Dec 18, 2008 5:53 pm Post subject: |
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Boobies and Beer?
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SYC
Joined: 16 May 2006
Posts: 269
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| Posted: Thu Dec 18, 2008 7:35 pm Post subject: |
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| Mark_A_W wrote: | | SYC is asking about Cathode Current Limiting I think. |
I did mean this. So what is the really CR of CRT in common film scene. I am wondering why 9" LC has so poor ANSI CR 150:1 as Dave mentioned, but still make a stunning picture.
SYC
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Thu Dec 18, 2008 8:19 pm Post subject: |
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| SYC wrote: | | Mark_A_W wrote: | | SYC is asking about Cathode Current Limiting I think. |
I did mean this. So what is the really CR of CRT in common film scene. I am wondering why 9" LC has so poor ANSI CR 150:1 as Dave mentioned, but still make a stunning picture.
SYC |
poor ANSI CR is due to the reflections in the lens.
plasmas and CRTs would melt themselves and cause a city-wide brownout if their full field white was "full" power. So, they limit the current when it gets to high.
ANSI lumens is a very exacting measurement of how much light a display can produce on a full white field adjusted to meet specific standards. On a CRT, this light output is very low due to the current limiting (ANSI lumens of about 180).
Due to the current limiting, plasma and CRT vendors prefer to quote "peak" lumens. This is generally what can be done on a full white window covering only 10% of the display area. Here vendors quote things like 1300 lumens from a CRT (though properly calibrated is much lower like around half or less).
Compare a 10% white window to a 100% white field on your CRT--the difference is huge. The white of the 10% looks "right" while the 100% looks dingy white or light gray.
So, lets talk about you point up there--why does CRT look great despite poor ANSI CR. The simple answer is because you've never seen great ANSI CR.
35mm film has a peak possible ANSI CR of about 400:1. However, after generational losses and such, the film you see projected at your local theater has an ANSI CR of about 100-130:1--or about the same as an LC CRT. The TV you grew up watching also had a bad ANSI CR. So, you are used to it, you have not seen high ANSI CR displays.
OK, next part of the equation is "Average Picture Level" or APL. Lets consider out full white field. 100% of the screen is 100 IRE, so the APL is 1.0 x 100 = 100. Let's consider the 10% white window, the APL is .10 x 100 = 10.
So, we know a CRT looks great with low APL scenes but weak with very high APL scenes. Now is where the argument starts!
No one measures light output at 50 or 60 APL. In other words a 50% white windows. So, what is it?
Secondly, what is the APL of "bright" content like Madagascar? 40%, 50%, ??? It is usually not calculated, but my guess is that that is around 45-55% whereas scenes in movies like Ice Age and Happy Feet can hit 70%.
So, the CRT is doing 180 lumens at an APL of 100 and 500+ lumens at an APL of 10. What is it doing at an APL of 50?
I've had alot of digitals in my theater to compare to CRTs and this is my opinion based upon observations and knowing the output of the PJs. A typical CRT on typical bright content look VERY much like PJs in the 280 Lumen range. PJs of 350 lumens or more look significantly brighter than a CRT on content like Madagascar, etc.
One last comment about ANSI CR. ANSI CR only maters in scenes with high dynamic content (in other words bright and dark objects together). This can only occur on bright scenes. On low APL scenes (dark scenes in movies), there is not enough of a difference between the "bright" and the "dark" parts for ANSI to matter--so a 647:1 ANSI CR and a 150:1 ANSI CR will look about the same. BUT, this is where on/off CR and black level is king. If a PJ has a high black level, the dark scene will not look realistic, but washed out.
So, let me give a couple examples.
My last PJ:
on/off CR: ~20,000:1 (typical properly calibrated gamma modded CRT in batcave).
ANSI CR: 130:1
ANSI/Peak Lumens: 180/~500
Current PJ:
on/off CR: 3800:1 (D65 calibrated) with a definate "dark gray" black (a bit better than the black you see in a movie theater).
ANSI CR: 647:1
ANSI/Peeak Lumens: 380/380
Now, lets consider two scenes:
1) The initial battle scene in Gladiator, and
2) The initial zoo scenes of Madagascar
On number 1, the CRT renders this completely convincingly. It is truly like you are there in the dark early morning. The current PJ however looks more like a movie in a movie theater. All the details are there, great shadow detail, you know exactly that it is early morning and all that, but it doesn't look quite real because it is "too bright." The scene looks a little less 3D on the digital (neither look that 3D in low APL though).
Now, on number 2, the CRT looks good. Show the scene to anyone a a reasonable screen (mine was 92" wide 1.2 gain) and it looks good. But, flip on the digital and it is like "holy $h!t batman!" It is way brighter. Has WAAAY more pop. The scene looks more dynamic, more "real", more 3D by a good bit.
To this day, there is no properly calibrated projector that can achieve an ANSI CR of over 500:1 and an on/off of over 20,000:1. JVC is getting close, but they are not quite there yet. When this comes, it will be an incredible projector.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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SYC
Joined: 16 May 2006
Posts: 269
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| Posted: Sun Dec 21, 2008 6:00 pm Post subject: |
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Dave, thanks for detailed explanation. I own a XG-110 and it give me a great picture quality. I am wondering what is the main feature of CRT to make a great picture quality and still be unbeatable today.
SYC
Last edited by SYC on Mon Dec 22, 2008 7:11 am; edited 1 time in total
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km987654
Joined: 25 Jul 2007
Posts: 2874
Location: Australia
TV/Projector: Barco BG809s
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| Posted: Mon Dec 22, 2008 4:02 am Post subject: |
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I have, over time, read many of Daves threads and as always they are detailed and accurate. We are lucky to have Dave. There have also been many threads over which is better digital or CRT. To me Dave has demonstrated a view that I have always maintained and that is a comparison is not useful. Each type of PJ produces its images based on different technology and will excell under different circumstances . You either like one or the other or appreciate both for what they are.
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Person99
Joined: 09 Mar 2006
Posts: 4899
Location: Flower Mound, TX
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| Posted: Mon Dec 22, 2008 6:53 pm Post subject: |
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| SYC wrote: | | I own a XG-110 and it give me a great picture quality. |
Yep, it does.
| SYC wrote: | I am wondering what is the main feature of CRT to make a great picture quality and still be unbeatable today.
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You trying to goad me? 
My opinions are pretty unwelcome here, so I'll be likely fading into the background and not monitoring this thread, so feel free to PM me here or AVS if you want.
Basically, the "still unbeatable today" claim is very much up for discussion these days. I don't think Art thought that he was getting a picture of lesser quality when he pulled down the G90 stack to but up a DLP (HT5000). I know some folks in San Jose right now pulling out a 9500LC and replacing it with a C3X--they don't think they are getting less picture quality at all.
Guy Kuo has been pulling out XGs and replacing them with RS2s and RS20s the last year and neither he nor his customers think they have a worse picture than the XG.
So, I can't really agree with the "unbeatable today" comment. There are about 2 to 3 dozen people in the world that will agree with that statement (and they are all on this forum), but in generally, no industry experts or avid enthusiasts would accept this as the truism it was 5 years ago.
That said, every tech has its strengths and weaknesses. The problem with comparing CRT to "digitals" is that while all CRTs are very similar, the digitals are not. So generic comparisons break down quickly. As far as picture quality differences, in general CRT excels in the following areas:
- black level
- handling of motion
- dynamic range
- lack of pixel structure (All digital data is made up of little squares or rectangles [HD is squares]. Digital projectors render these exactly as on the source, thus angled lines can have "stair stepping"--a CRT turns these into a overlapping round "dots" with brighter cores and softer edges, thus no stair stepping).
Current "Digitals" tend to exceed the CRT int he following areas:
- picture uniformity (corners are nearly as bright as the center)
- corner focus
- image brightness
- ANSI CR
- Resolving power (much higher MTF)
- great shadow detail
Other things that could be considered are ergonomics (the digital far exceeds CRT here) and reliability (the CRT far exceeds digital here). But, we'll focus mostly on image quality.
Even though each tech has its strengths and weaknesses, the weaknesses of CRT where not as bad as the weakness of digital (i.e. digitals black level and pixel visibility were REALLY bad). A few years ago we started to see digitals that could "overall" complete with CRT. Their weaknesses were not as bad and their strengths were really strong. However, they cost 2-4 times as much as comparably performing CRTs (A qualia 004 was $25,000 when minty 9" machines where $8000-12,000 for instance). So, going with a CRT was a no brainer--deal with the ergonomics, get a great picture for the money.
But, things have really changed a lot in the last year. Digital tech has matured considerably and come down in price. Now the landscape is much more competitive. Now, it is like what was said above, it is more about what you like.
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Dave
A train station is where the train stops. A bus station is where the bus stops. On my desk, I have a work station....
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VideoGrabber
Joined: 09 Apr 2006
Posts: 933
Location: Michigan
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| Posted: Mon Dec 22, 2008 9:13 pm Post subject: |
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Dave presents a good summary of the strong points of both technologies above. Digitals have come a long way, and dropped massively in price at the same time. Both good things. One of the points I think he's trying to make (in many places) is that some of them are now contenders, where they weren't before. And they'll likely keep improving.
What some tend to overlook in all the flamefesting is that CRTs still throw a fantastic picture! Even Dave agrees with that, though he doesn't say so as much anymore as he used to. Who cares if "still unbeatable today" is always going to be true? There are still valid reasons to go with (or stay with) CRT today. And lest we forget, while digitals have come down in price, used 8" PJs have also dropped significantly in price at the same time, making them an even more affordable opportunity than ever before. Yet the quality is just as good as always, with reliability as well.
Whether they're "best" or not is an individual decision, that each person gets to make for themselves, based on their priorities and imaging criteria. It's no longer a "CRT uber alles" situation any more. There are choices, and in my book, that's a good thing.
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Chuchuf
Joined: 11 Mar 2006
Posts: 548
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| Posted: Mon Dec 22, 2008 11:57 pm Post subject: |
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Nice writeup Dave.
What I find ironic is that today, the CRT is still being use as the de-facto standard to beat, just as it was years ago when digital didn't stand a chance.
Terry
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SYC
Joined: 16 May 2006
Posts: 269
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| Posted: Tue Dec 23, 2008 8:12 am Post subject: |
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Dave, I learn much from you.
SYC
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