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Z1: greyscale experiment

Discussion in 'Projectors, Screens & Video Processors' started by ROne, Mar 2, 2003.

  1. ROne

    ROne
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    This is something I posted across in the american forums, but I though might be interesting to you lot:

    I've had my z1 for 3 months now, running using HTPC + TT 1.5.23, my screen is a HCMW, removed from the mechanism and stretched over a wooden frame to get rid of the creases.

    I have used many of my own tweaks from the Factory and service menu to remove Vertical Banding, I have also taken the prism out to remove difficult dust blobs (check other post in my name for info.)

    So really the only thing left to get right for me was the grey scale, while I wait for the smart to make its Z1 debut I have literally been eyeballing it with no reference, which produces very inaccurate results.

    What I decided to was to bring my broadcast monitor home ( a jvc model that is set up for D6500 and 9300) and simultaneously run grey scale charts on the monitor and the z1. I knew this method would only get me within a certain amount of accuracy but would at lest tell me how far out I was.

    Well I booted up avia in both and analyzed the vertical IRE steps, then examined them, I found initially that my "preferred" z1 settings with RGB were way too blue, a huge difference.

    R = 31
    G = 30
    B = 30

    After a few minutes I had adjusted my settings to:

    R = 36
    G = 36
    B = 30

    Which on the chart on the Z1 looked quite orangy, but this was close to what the monitor was displaying so I went with these numbers. On displaying individual IRE squares I noticed that the 20,30,40 IRE were not blue enough (which just shows you how non-linear the IRE greyscale tracking is here.) after adding a lot of R and G. So I then went into the service menu to see if I could find which settings controlled the lower end of IRE. (BIAS I believe?)

    Working with settings 10 -15 which I believe have control over such parameters I found these settings to be the best.

    10 = 200
    11 = 203
    12 = 198
    13 = 156
    14 = 135
    15 = 157

    I will be the first to admit I am probably messing around blind here and I can't give any actual advice what would be the best settings for anyone else but I guess you have to start somewhere.

    The greyscale still isn't perfect, I still can't get that top end orange into to white's that the monitor could show, however ironically I thought that upping the green with the read would produce a terrible image but not so it looks to contain more depth now especially in darker scenes.

    I have stored my previous settings and one thing is for sure they are definately too blue, but I got used to this.

    My final settings are: (Room totally blacked out and firing onto Da-lite HCMW screen.)

    TT controls = B,9 C,100 H,0 SAT,100 GAMMA,1

    Z1 Settings

    C = 35
    B = 32
    R = 36
    G = 36
    B = 30
    Gamma = between 10-12 (12 on most material though)

    I realise that these settings won't be correct for anyone else and people will say that you shouldn't calibrate to a source but the point is, it is one stage better than calibrating to NO reference, and I await the smart III for further accuracy.

    ROne.
     
  2. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Rone: Your method of optical comparison is the one the very best ISF guys use. By using a calibrated monitor though and feeding it the same signals you should have been able to get pretty close.

    If there are numbers for bias then there are probably numbers for gain as well. I'd set your normal menu RGB settings to flat and use the service ones to do the cal again. Nice work.

    Gordon
     
  3. ROne

    ROne
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    Thanks for the encouragement, I was kinda half expecting a dressing down from someone but hey you never know.

    So do you include yourself in this methodology or do you calibrate with a device?

    I'll try starting with the RGB flat, thanks.
     
  4. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    To use an optical comparator (which basically outputs light at D65 at a continuous intensity) requires great experience and patience. This is because comparing D65 bright patch with a mid intensity reference isn't easy. I am awaiting my spectroradiometer. That's the expensive way out:)

    No-one should be dressed down for playing with their own projector just as long as they understand the risks involved if it goes wrong. To try and do a calibration without a reference would have been much more difficult.

    Gordon
     

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