Calibrating the Infocus X1 with AVIA, some help needed.

Discussion in 'Displays' started by Inspector Hammer!, Oct 2, 2005.

  1. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    I've had my X1 for almost 2 years now and think that I have it pretty well calibrated using my good ol' AVIA disc, but I just want to see if i'm doing it right in two area's, black level and white level.

    Now, on the black level test patteren, I have my black set as instructed on the tutorial, so that I can just barely see the vertical bar on the right moving back and forth but cannot see the left one. Is this correct for a projector?

    On the white level test patteren, I use the lower portion of the screen and pretty much set white the same way as black, only this time I set it so that I can see BOTH vertical bars moving back and forth, with one just brighter than the other. Is this correct?

    If i'm doing something wrong please let me know and point me in the right direction, i've calibrated countless CRT sets with AVIA and have that down, but I just want to confirm that i'm using it correctly on a DLP projector such as the X1, thanks. [​IMG]
     
  2. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Gregg, Vince, Guy...anyone? [​IMG]
     
  3. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    I'll give this one more shot before I let it slide off the page, I just need instruction on setting black and white levels on my Infocus X1 using AVIA.

    Please, I need to know if i'm using AVIA correctly on a DLP projector.
     
  4. ChrisWiggles

    ChrisWiggles Producer

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    On a digital display you want to maximize your contrast range as much as possible. On an DLP like the x1, you can use mirror dithering to set black level with extreme precision. Throw up any of the black patterns, and observe the black background, which is at video 16 (black). You should set this so that the mirrors are off, or one click above this so that you see them dithering. You should see both black bars on the Avia patterns, as they are encoded above black. There is no below-black elements on Avia.

    For white, on a digital display you are looking for clipping or colorshifting. Some displays will hard-clip white, and others will clip at one color before the others which will show as a colorshift. Note how this is very different than calibrating a CRT's white level. Both of the moving bars on Avia are below reference white(235) so they should ALWAYS remain visible. You should raise your white level until the larger white portion (which is brighter than the bars) begins to colorshift, or you begin to see that portion clip down until the bars below white are no longer visible as distinct from white. You should stay a few clicks below the point of clipping or colorshifting. This will maximize your white point.

    Now, you may want to return to black, and go back and forth between black and white a couple times as the controls may interact, so it is an iterative process.

    ***advanced note: It is preferable for some demanding viewers, to align the peak white of a digital display to peak white 254, rather than reference white 235 so as to prevent any peak white highlight detail clipping. This will reduce the contrast range between black and reference white slightly, and your in-scene contrast will be slightly less, but you will maintain data the extends beyond reference white. This is a subjective choice by the user on displays that have limited contrast ranges, unlike the unlimited range provided by CRTs that does not prompt this choice. To do so, you will need to use patterns that extend to peak white, such as those on Avia PRO, or DVE.
     
  5. Jim Mcc

    Jim Mcc Producer

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    John, I also have the X1, but I don't have Avia. I hope you can understand what Chris said, because I sure don't.
     
  6. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Well, it took me a couple of times reading his post, but I think I got the jist of it. Basically what he's saying is that you should see BOTH moving vertical bars on BOTH the black and white test patteren, turning the black and white level up or down until one bar is visible and keeping the level at just before the point where the other bar next to it disappears into the background.

    I can see how you would get confused, Jim, if you had AVIA and were familliar with it's patterens it would be clearer to you. You should most definitely look into picking up AVIA, it's an INVALUABLE HT tool and I don't see how I got along without it. [​IMG]

    BTW, Chris, I made the adjustments last night based on your post and I must say that I am impressed with the results! It turned out that I had the black and white levels down one notch too low which resulted in my image being too dark, which was my #1 complaint about the X1, but those adjustments perked it right up and it looks very good now. [​IMG]
     
  7. ChrisWiggles

    ChrisWiggles Producer

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    That is correct. All the moving bars in Avia are *within* the range from black to white. The black bars in Avia are both *above* black. The white bars are both below white. If the bars are clipped off, then you are losing shadow detail near black, and obviously you'll be losing white detail near white.

    The black bars may become obscured using a very high APL pattern (like the half-white pattern in the advanced menu) if your system has very low ANSI contrast. With most digitals, however, this is not really a problem because the black level of the display is elevated enough, and ANSI contrast is high enough that the visibility of the bars doesn't really vary with APL. On CRTs, this is more complex, because if you throw up a full black pattern with the bars and calibrate, then switch to one with half gray or white, ANSI washout will render the bars invisible. On CRTs then it is a little more complicated because the ultimate black level you arrive at will vary depending on the APL of the pattern, and the pattern you choose can depend on your preference for total black-out, or rendering all the shadow detaisl even in bright scenes (high APL).
     
  8. ChrisWiggles

    ChrisWiggles Producer

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    And remember, if you have a DLP, use dithering to find your black point by going up to the screen and observing the dithering. This will provide extreme precision compared to paying attention to the bars. Just observe the black background and find the point where the pixels start/stop dithering, that's your display's black point. At this point, the bars should all be visible, because they are all above black (on Avia; on DVE there are additional bars that are below black).
     
  9. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Chris,
    can you please explain what 'dithering' is for me so that I know exactly what to look for in the image? Thanks.
     
  10. Jim Mcc

    Jim Mcc Producer

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    John, I have the calibration disc from Sound and Vision. The test patterns sound the same as Avia, as it is made by Ovation Software(the same people that make Avia).
     
  11. ChrisWiggles

    ChrisWiggles Producer

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    Dither is how a DLP chip creates a grayscale. The DLP mirrors only have an ON and an OFF position, so white is full on, and black is full off. Everything in between is a ratio of how much time the mirror spends flipped on to flipped off. This happens extremely fast, so you don't see the mirrors flipping, however very close to the black point, the mirrors are mostly completely off, but flick on just a few times over a period of time to be slightly above black. If you go right up to the screen, even on paused video, look at dark objects and detail and you can see a sort of "dancing" on the screen as the pixels try to create light output that is very close to black.

    If you pay attention closely to this dithering right at the screen, you'll see that as you lower your black level, at some point the detail that you are observing will plunge below the black point on the display, and the pixels will stay completely in the off position and the dithering will dissappear. This is the black point of your DLP display. So, then use any pattern with video black, and use the black portion of this test to align black to this point on the display. I hope that helps and makes sense. You have to go right up to the screen and look closely at the pixels, and you should immediately see what I'm talking about, and then play around with your black level control and you'll see the dithering dissappear and re-appear as you move your black level down and up again. By paying attention to this dithering, you can identify very very precisly the exact black point of your display and align a test pattern to it.
     
  12. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Okay, I can see what your talking about, the dithering presents itself as millions of tiny particles moving vigorously in the black, the problem is, when I finally reached the point where the dithering disappears, the moving vertical bar on the left is completely gone while the one on the right is just BARELY visible.

    I was under the impression that both had to be visible for a DLP display.
     
  13. ChrisWiggles

    ChrisWiggles Producer

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    Yes, both should remain visible, though they may be obscured by ANSI washout. Try using a pattern with lower APL. If you are using Avia, there is a full-black+moving bars pattern that may help.
     
  14. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    I'm on that petteren right now, I put my nose right on the screen and I saw the dithering completely vanish at the 50 mark on my projector, I have to see of both bars are still visible at that mark...
     
  15. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    On the 'black bars' test in the grey scale area of the disc, I can make out just one bar, the right one, moving back and forth, the left is completely gone at the 50 mark where the dithering vanishes.
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    This is strange. If you raise it one click is the bar visible and the background just starts to dither? The point where the bar dithers and the background dithers should be at different points because the bar is a few levels above the background black. Unless the adjustment is quite coarse on the X1 this is somewhat strange.

    What does one click up look like?
     
  17. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Alright, I think I have it, I can't keep the projector's black level set at 50 where the dithering goes away, but I kicked it up one notch above it which is 52, my projector skips 51 for some reason.

    Now, the dithering is introduced at that point, but the moving bars appear as described and the dithering is very minimal, I think that that's the best I can do with AVIA. the image looks great, though.

    Thanks, Chris, for all of your assistance and for educating me on what dithering is and how it effects black level. [​IMG]
     
  18. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Hello again. [​IMG]

    Which bar do I look at to watch for the dithering, right or left?
     
  19. ChrisWiggles

    ChrisWiggles Producer

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    Hi! [​IMG]

    hehe, you look at the black *background* for dithering, as the background is black. The point where it starts dithering is the projector's black point, so you are aligning the black background with this point on the projector. At this point, BOTH bars should be visible (except when they may be obscured by washout from bright parts of a pattern if applicable). Remember that both bars are ABOVE black and should remain visible if the projector's black point and the black background of the pattern is aligned correctly.
     
  20. Inspector Hammer!

    Inspector Hammer! Executive Producer

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    Okay, we're on the same page then, I was looking at the background. And yep, what I said in post #17 is true, I can't achieve total absense of dithering and keep both bars visible at the same time, i've tried it a number of times now.

    52 seems to be the sweet spot for black on my projector, 53 is too bright making my blacks look foggy and 50 is too low because I can only see one bar at that point.
     

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