How Do DLP Produce Deep Black Compared to CRT-RPTV?

Discussion in 'Displays' started by Arthur S, Jul 20, 2005.

  1. Arthur S

    Arthur S Cinematographer

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    For me, the ability to do deep black adds considerably to my viewing pleasure. If I were going to choose between a top of the line CRT-RPTV and a DLP-RPTV which would give me the better blacks?

    Thanks
     
  2. Neil Joseph

    Neil Joseph Lead Actor

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    Short answer is the CRT will give better blacks.
     
  3. ChristopherDAC

    ChristopherDAC Producer

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    There's no doubt, though, that they work better than either the old analog light-valve projectors ["Eidophor"] or transmissive LCDs in that respect, and they keep getting better. If you're really willing to spend the big bucks, though, you can still get a CRT which outperforms anything wlse on the market.
     
  4. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    The DLP RP unit just can't partially turn off its light bulb. It's always on in the background.

    The CRT simply does not have to scan a certain area to create its blacks. The absence of electrons exciting the phosphors ...

    But the days of CRT RPTVs are quickly drawing to a close.

    Regards
     
  5. jim.vaccaro

    jim.vaccaro Second Unit

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    You think so? Man, I hope not.

    Especially with thin-CRT tech on the very near horizon from Samsung and others. I was kind of hoping for a CRT rennaisance.
     
  6. Arthur S

    Arthur S Cinematographer

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    jim

    Thin CRT is in store now. 30 inch Samsung Slimfit has been available at Best Buy for about 6 weeks now. Other companies are coming out with their own thin CRT.

    This is not going to have any effect on CRT-RPTV though as thin CRT will be limited to 34 inch and is direct view. CRT-RPTVs start in the 40s and go up. So they are not competing.

    But it will improve sales of direct view CRT somewhat although the weight of these DV-CRTs is not much less than full depth models.
     
  7. jim.vaccaro

    jim.vaccaro Second Unit

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    That's good info, thanks, I didn't know they were out already. I'm in Iraq, and henceforth don't get out to Best Buy much. [​IMG]

    I was hoping thin-CRT would have uses in RP TVs as well. 34 inches is nice and all, but....
     
  8. Leo Kerr

    Leo Kerr Screenwriter

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    I always hope when I hear "slim" with TV that someone's talking about Field Emission Displays... (at least I think that's what they're calling them... where you use a CRT/phosphore type setting, except each pixel has its own emitters.)

    Leo
     
  9. ChrisWiggles

    ChrisWiggles Producer

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    Keep in mind the difference between on/off and ANSI contrast. CRT absolutely holds the throne with on/off contrast, which means that very low APL scenes will look superior. However, CRTs have low ANSI contrast, while DLPs tend to have pretty good ANSI, which means that in mixed-scenes and higher-APL material the DLP may achieve better blacks within a scene, but will still suffer and appear gray in the very dark stuff. Just a picky note to mention, however also keep in mind that the room environment has a HUGE effect on ANSI contrast, so you won't see this difference unless you are in a very well-designed dark and flat-painted room.
     
  10. Arthur S

    Arthur S Cinematographer

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    >>>>keep in mind that the room environment has a HUGE effect on ANSI contrast, so you won't see this difference unless you are in a very well-designed dark and flat-painted room.
     
  11. ChrisWiggles

    ChrisWiggles Producer

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    Meaning, a DLP projector has higher ANSI contrast numbers on its own, but ANSI contrast is *very* heavily affected by the room environment. If you put a CRT side-by-side in a light-colored room, you'll never see a difference because the room's effects on ANSI will totally obliterate any visible difference between the two machines in ANSI capability. However, if you view both machines in a room that's completely covered in black velvet, you will be getting the maximum ANSI out of both machines, and the difference will be much more visible as additions of room spill will be pretty much completely eliminated.

    For instance, a good single-chip DLP may achieve say 300:1 or 400:1 ANSI contrast, while a non-LC CRT will achieve maybe 30:1 ANSI, and an LC CRT may get close to 100:1 ANSI, but all of this measured in a completely black velvet room. If you put all those projectors in a white room, your ANSI numbers might be like 5:1 or something really horrible, and indistinguishible between all 3 machines.
     
  12. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    Odd, I consistently get 150-200:1 ANSI on CRT sets all the time.

    Regards
     
  13. Arthur S

    Arthur S Cinematographer

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    Michael

    I never heard of a non CL CRT.

    Just simply does he mean that a DLP can only do good its best blacks in a dark room? And that in a dark room a CRT-RPTV won't have much of an advantage over a DLP in the same dark room?

    Thanks
     
  14. Michael TLV

    Michael TLV THX Video Instructor/Calibrator

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    I hate acronyms. I have not heard of what the CL part of that means.

    A problem with all RPTVs is that the screen the image sits on is not neutral ... Project black onto something that is gray-white and you don't have black anymore. And of course LCD and DLP RP screens have some green in them (so they look better when they are turned off). [​IMG]

    I'd still take a CRT RP unit in the dark over a DLP RP unit because I don't like my blacks to have that grainy/green effect that DLP blacks have. But of course there are lots of advantages both ways for either technology and each person has to pick which ones he likes more that others.

    REgards
     
  15. ChrisWiggles

    ChrisWiggles Producer

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    Sorry guys, sometimes I assume folks can read my mind, and then I forget what the thread was about (RP units, not FP steups)! :b

    Anyway, LC= Liquid coupled.

    The numbers I quoted are actually for FP systems, but they carry over to RP implementations. My fault for being vague and not seeing that this was RP-specific.

    I am a CRT guy, so I'm with Michael there, but what I was saying is that there are two attributes to consider to judge "black" performance. There is the on/off contrast range, which is the difference between a full-white screen, and a full-black one. This gives you how utterly black a display can get. CRTs here are king, nearly infinite on/off CR capability. Digitals have very limited on/off CR except for the neqest units, which are still short of CRT on/off CR.

    The other attribute is ANSI contrast, which is measured with a checkerboard pattern, meaning that white and black are shown at the same time. This reveals how well a display can "maintain" it's black as bright objects populate the screen. There is always spill from bright objects onto other parts of the screen, so your "black" will actually be a lot grayer in a real-world scene with bright objects in it, than it would be if it were just a full frame of black. Here, CRTs by their nature, are fairly poor, and projection CRTs with air-coupled optics instead of liquid coupled optics suffer even more in ANSI contrast. However, digitals tend to have better ANSI capability, so in bright scenes their blacks may seem deeper, while a CRT may wash out more.

    This is why it sort of depends on what kind of APL a scene you are looking at, to decide what display has "better blacks." It varies on APL, with very low APL scenes CRT rules the day, at high-APL material, digitals can have an edge. However, ANSI contrast is a fragile capability, and can be ruined by all sorts of other sources of spill, namely the room and dirty lenses, mirrors, reflective interior cabinets(this is why people line RPTVs with dark fabrics, etc), so the ANSI benefit that digitals may have may be totally obliterated by other factors beyond the display's actual capability. On/off CR does not suffer this, as long as there is no ambient light in the room.

    Anyway, sorry if this got a touch advanced, but that's the reality of things, they're a bit complicated sometimes.
     

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