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Setting white and black levels

Discussion in 'Projectors, Screens & Video Processors' started by Gary Lightfoot, Mar 2, 2005.

  1. Gary Lightfoot

    Gary Lightfoot
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    Does everybody here know how to set their white and black levels using Avia or DVE? If not, I'll post some images so you can see what to look for and what chapters they are on the disk. DVE is a bit of a pig to navigate.

    Any other ideas for stuff like this?

    I still think a calibration 'sticky' would be a good idea so that it's easily visible and helpful to newcomers, so how do we go about getting it done?

    Gary.
     
  2. theritz

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    Gary,

    That's a great idea - I'd say the setting white and black levels along with sharpness are the keys to good image quality. A "walkthough" Avia or DVE with screencaps would be a good reference resource.

    I also agree that a calibration "sticky" would also be good - you should just start the thread now, and then PM Kramer or Stuart and request them to "sticky" it. You could ask folk not to use the thread for discussion, but to submit stuff to be added to the thread, in the same way as the FAQ has been built.


    If you want a hand with anything, drop me a PM.


    Regards,


    Sean.
     
  3. GrahamMG

    GrahamMG
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    HI Gary.
    Excellent idea, DVE is, as you say, "difficult" to navigate around and no doubt any form of instruction will help people out...
     
  4. Bristol Pete

    Bristol Pete
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    I will third that.

    I put AVIA on last week and though I got it - so to speak, but my little bottom shrunk at how much info was on there and exactly HOW MUCH i did not know how to do.

    I am still waiting for Gary to head over to Hotel Benefit to do mine for me. Har har....

    Cap.
     
  5. Gary Lightfoot

    Gary Lightfoot
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    Hi sean,

    I totaly agree with the white and black levels being probably one of the most important settings you can do with a pj, and as it's often something that's overlooked and can be a cause of image problems, it could be useful for those that aren't sure how to go about it.

    Graham,

    Thanks, let me know what you think.

    OK, here's a couple of images I knocked up, so hopefuly it'll be useful for some people out there. If there are any errors etc hopefully someone will let me know. :)

    Edited to add digital level values and ire values to image.
    Edited to add example of an incorrectly set brightness levels - the 3rd image has simulated image noise whih would be noticable because it would be constantly moving like 'mosquitos'.
     

    Attached Files:

  6. Gary Lightfoot

    Gary Lightfoot
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    To adjust the black level, you use the brightness control, and to adjust the white level, you use the contrast control. One will effect the other, so you will have to go back and forth between them till it's right.

    If you can't see the moving black bars, or only one of them, you may have to adjust the gamma on your player, or the brightness if it has one. Idealy you should do most of the adjustments on the display, but that's not always possible.

    On Avia, using the all black screen with the moving bars (T1 chapter 4) will allow a more accurate adjustment of black, as the above image is bright and will cause the iris to shut down so you won't see the black bars so easy.

    DVE has a 3 black bar PLUGE pattern that is OK for black level, but there doesn't appear to be a similar white level adjustment suitable for digital displays, which is why I think the SMPTE pattern could be more useful, Any suggestions welcome of course.

    The above images have been made brighter than they should be just to make sure the bars and boxes are visible.

    Forgot to mention - Avia is for NTSC, and DVE is available for either PAL or NTSC, though the PAL version is available more readily here in the UK.

    Gary.
     
  7. RTFM

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    Good thread Gary.

    I can't stress enough the importance of getting the basic building blocks right.

    A PJ set-up Sticky on this DLP/LCD PJ Forum is a must.

    Go for it :thumbsup:

    Jeff :rtfm:
     
  8. Gary Lightfoot

    Gary Lightfoot
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    Hi Jeff,

    Thanks for the thumbs up. :)

    I think I should mention that it was Jeff that brought Avia to my attention a few years ago now, and it was him that showed me the basics. He's helped me pick up a lot of other useful information since them, so I'm very greatful. Thanks Jeff!

    If you notice any errors, or can see room for improvement, please let me know OK? :)

    Gary.
     
  9. Bristol Pete

    Bristol Pete
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    We all Love Jeff.

    Jeff for Prime Minister. :D

    The RTFM Manifesto.

    Point 1.

    A projector for everyone.


    um...........thats it.

    ha ha.

    Cap :)
     
  10. GrahamMG

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    Yep, I was about to say that I would hope you got the levels much better than that :rotfl:
    I can see loads of people on Amazon today ordering up a copy of DVE. It would also be worth pointing out that if you view both NTSC and PAL material you should check both formats as levels can be different.....The question of if you can adjust these spearately is a whole new ball game..... people have to decide for themselves if it is bad enough to warrent investment in a pj that can.....Some have pretty obvious differences in black level between NTSC and PAL.....
    I can see us straying quite quickly into other areas of the test disks that people will want to know how to navigate around so a sticky is a must really if this is to become a "bible" for the basics. Maybe Gordon has a typed up missive that doesn't do him out of a job (not likely as many couldn't afford the kit he wheels around to do the full calibration setup!).
     
  11. GrahamMG

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    BTW, anyone want to venture into explaining IRE?
     
  12. Kramer

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    Yep, great idea Gary :smashin: .

    If you want to spend a few days working on this with Sean & others, it may be better to start a new thread, which I'll sticky.

    I'd suggest the first post contain relevant info with discussion below or in a separate thread (linked to from the calibration sticky).

    Your good work will be appreciated by the community :smashin: .


    :smoke:
     
  13. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    On DVE there is a pattern that has over 100ire to under 0 ire vertical bars going from left to right at top and right to left at bottom. You can use this to set contrast. It's in TITLE 12 as is the 20re pattern I talk about for brightness

    Above the white bars you'll see 3 black dots. The white bar to the left of them is over 100ire. You want to be able to see it. On some devices you can't as the information is clipped by the players or the displays processing. You should try adjusting contrast down or input level....or gamma possibly to make it visible.

    Their 20 ire pattern with the three black bars is a good one for setting brightness. You actually want to see all the black bars but if you do this with a device like a DLP or Plasma you have a danger of seeing alot of noise in the dark areas of the image. The darkest bar is blacker than black and the black background is 0ire. On a plasma or DLP if you stand beside the screen and adjust brightness up and down you'll see the point at which the display becomes as black as it can.....look at the 0ire background and the blacker than black stripe. You'll see the dancing black pixels all around the blacker than black stripe. I'd recommend adjusting the brightness control downwards until the dancing pixels in the background go away and the 0ire section looks silent like the blacker than black stripe. It should be noted that HD2 DLP's and earlier will always have this noise in the 0ire section and in that case you just have to match the noise levels of the blacker than black and 0ire sections.

    Sorry no pictures but I'm in a hotel room not at home...perhaps Garry can take some.
     
  14. Gary Lightfoot

    Gary Lightfoot
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    Graham,

    Yup, the differences in black levels and what ire levels are as well as digital levels, PC and Video levels was something I have written about before and will put up for the sticky.

    Gordon - thanks for that. I'm not that familiar with DVE so I really appreciate your input there. I'll do another diagram. Should it replace the SMPTE do you think?

    Kramer,

    Thanks! How about we put up the info we think is relevant in this thread first, then when everybody is happy with the content, we put it into the pukka sticky? That way any errors can be corrected or improvements made so that the sticky is pretty much good to go once it's up?

    Cheers.

    Gary.
     
  15. Kramer

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    Sounds good Gary :smashin: .
     
  16. Gary Lightfoot

    Gary Lightfoot
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    NTSC and PAL black levels.

    Here in the UK, PAL uses 0mv for black, and 0.714mv for white. In North America they have a 'setup pedestal' in their NTSC system which uses 0.53mv for black. Japan is NTSC, but doesn't have setup, so uses 0mv the same as PAL.

    DVDs store information digitaly, and black is stored as Digital 16. On your PCs paint programs, you may have noticed that colours are represented as RGB values, such as R255, G255, B255 which is white. 0,0,0 is black. PC levels are 0 to 255.

    Video, sometimes referred to as sRGB uses values from 16 to 235. When a DVD player is presented with Digital 16, it knows it is black and depending on the system, will send out a voltage accordingly - for PAL (the DVD will have a PAL or NTSC 'flag' to tell the player which system it is), 0mv will be sent to your display, so for your display to correctly show Digital 16 as black, it must be set so that is showing black correctly at that voltage, and a test disk (Avia, DVE) will help you to do that.

    The same should be done for NTSC as the DVD player will send a 0.53mv signal for Digital 16 (black). HTPCs don't have to worry about NTSC and PAL as it doesn't have PAL and NTSC transmission standards to worry about, it just sends out a progressive image via vga or digital via DVI. The software DVD player 'overlay' is the part which displays the video image, and that should be as sRGB video levels and not PC levels.

    As you can see, black levels for PAL and NTSC are different, so if your display has memories for different inputs, or for different signals on the same input (most using DVD players will be sending all outputs down the same component cables for instance), it won't be a problem, because the display will remember the individual brightness settings for either signal.

    If the display doesn't do it automatically, then for proper black level and detail to be correctly displayed, you will have to change settings each time you change from one system to another.

    These voltages are sometimes referred to as 'ire' levels, and are merely a name for analogue voltage levels. 0ire will be 0mv, and 7.5ire will be 0.53mv, but both are black. 100ire is white. The ire levels in between are just names given to the voltages that are presented at different levels of grey.

    Edited:

    Below black refers to the black detail that may or may not be present below Digital 16 (0 to 15), and above white is 236 to 255. You won't see below black if the display is set-up correctly using a test disk though, but it is possible to see data above 235 unless the source or display clips that data as Gordon has said.

    Showing below black or having a raised black level due to an incorrect brightness setting on a digital display can also show up image noise such as mpg blocking and artefcats. Whilst a CRT display can happily do this with little negative impact on the image, with a digital, it can become intrusive enough to make the image noise distracting.
     
  17. Gary Lightfoot

    Gary Lightfoot
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    Gordon etc, let me know what you think. :)

    Edit to add pics of incorrect and correct contrast setting. I've simulated the look of an incorrect contrast setting for a better and more accurate representation of what it can really look like.
     

    Attached Files:

  18. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Looks good. I would mention though, that having had some discussion with Mr Kane specifically about the blacker than black bars etc, you should be able to see it. There is blacker than black detail just as there is whiter than white detail on alot of content.

    The issue is that on displays that do not have accurate gamma that matches CRT you can create more issues by allowing the bar to be visible. So if you have a CRT projector you may want to adjust so you can actually see the blacker than black bar. On a DLP or plasma I'd suggest not as you may just end up seeing more noise in dark areas rather than more detail. I suspect most CRT owners wont though as by doing it you are likely to end up with a more washed out image as they are not good at keeping black level constant regardless of picture content. It's all a balancing act....

    now I am not sure i want to give away any more info.....I'll be out of a job if I carry on like this...hahahhahahahah.

    Gordon
     
  19. PjPip

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    DVE suggests that you shouldn't be seeing blacker than black? Any true picture info should only be in the above the video black level shouldn't it? I also use the SMPTE pattern gary as my current Pioneer clips the signal anyway, meaning that no matter what the settings are I never see the below black bars on the vertical pluge page :(
    New player methinks :)
     
  20. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Well there is blacker than black info on the disc. It's recorded picture info. I asked Joe Kane about this specifically as it's always bugged me. This was at a demo of the Samsung DLP he co-developed with them. He agreed when I suggested that you should be able to see graduations from the voltage equivalent of bit0 to that of bit 16.

    To prove he wasn't making it up he stuck up that very pattern and low and behold both the DLP's he was using had been set to show the blacker than black stripe......I wouldn't advise trying it with a poor HD2+ or any HD2 pj though.....

    Gordon
     
  21. Boris Blank

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    Good useful stuff Gary (especially) and Gordon, well done! Now, how's about contrast (which I always find a pain to set accurately!).?
    Paul
     
  22. Gary Lightfoot

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    Hi Gordon,

    Great stuff again, thanks. :)

    There have been some discussions over on avs with the likes of Stacy Spears, and they've shown images which highlight the below black detail - I think the movie example in question had Leonardo DeCaprio in it. It's surprising how much image info is available below 16, but like you say, setting up the display not to show below black seems to be the more favourable approach for the reasons you mention, whereas allowing 'above white' seems more forigiving.

    I also find that the more I read from people like Joe Kane, Guy Kuo etc, the less I seem to know! It is a very in-depth subject to say the least. :) Any more hints tips or tricks appreciated Gordon - but I think you should mention that full ISF calibration cannot be done with a test disk alone. ;)

    Paul,

    By contrast, do you mean the white level? If so, the left hand image in post 17 can be used for PAL white level - use the contrast control so that the bar over 100ire/D234 (labeled D246) can be distinguished from the 100ire bar. Make sure that those two white bars don't blend into one, otherwise you'll be losing detail, or 'crushing whites' as some would say. For NTSC, the Avia needle pulse test shown in the first post is all you need.

    Did we mention that brightness adjusts black level, and contrast adjusts white level? That's important, so sorry if I forget to mention it earlier!

    Gary.
     
  23. Gary Lightfoot

    Gary Lightfoot
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    Any more input or requests for this thread before it gets transferred to a sticky?

    I'll post a pic of the ire bars from Avia for those that haven't seen them.

    Gary.
     
  24. GrahamMG

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    I very much doubt you will be out of a job, as I said earlier not many people will splash out on the full Milori kit etc. and even less people will know what to do with it!
    ANyone care to mention how gamma settings can be adjusted properly or even checked properly using DVE? I must admit that I tend to set 2.2 and leave well alone....
     
  25. Gary Lightfoot

    Gary Lightfoot
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    I'd like to know that too :)

    I've seen a gamma test pattern in Avia, but never got round to seeing how you use it. Gordon, Jeff? :)

    I did discover that increasing the gamma on the projector so that the image looked brighter had the effect of lowering the measured gamma when using Colorfacts, so that might help for adjusting gamma to get 2.2 if it's too high or too low.

    Does DVE come with blue glasses or colour gels like Avia? There's the blue bars test screen for setting saturation and hue which is usefull.

    What about CIE chart and D65 stuff? I can put one of those up as well. I'll try to do an explanation of D65 so we can see why it's necessary and why Gordon calibrates displays to that standard.

    Gary
     
  26. GrahamMG

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    DVE comes with glasses as well :smashin:
     
  27. Gary Lightfoot

    Gary Lightfoot
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    Go to DVE title 7 chapter 4, and you should see some coloured squares within a single coloured (reference) background (fig1). Use the blue plastic filter across the pattern (fig2) and adjust the colour control so that all the colours blend into the reference background (fig3).

    See the Calibration 'sticky' for the images.
     
  28. Gary Lightfoot

    Gary Lightfoot
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    I've added and manipulated some earlier images to give some better ideas of what incorrect settings can look like.

    Gary.
     
  29. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    On the colour bars Garry's posted.....if you have a CRT projector forget about the filters...just cover the requisite lenses and you'll get easier and more accurate setting.

    Also once you've used the blue filter check the green and red. You may find that there is more red saturation than is required. In this case you may have to reduce colour to get rid of the red push as it may be objectionable. Some display devices have seperate green and red saturation controls (Hitatchi plasma), You can use these to make this very accurate....Lumagen scalers also have this ability. The RGBCMY settings in Pioneers ARE NOT for these adjustments.....Leave them alone!

    Gordon
     
  30. Gary Lightfoot

    Gary Lightfoot
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    Thanks again Gordon. :)

    Is the red push you mention an NTSC decoder issue or is it a general issue? I thought PAL was free from that or am I confusing it with something else? Digital projectors have the opposite problem with red by and large though don't they - a red deficient lamp that needs correcting in the grey scale.

    Gary.
     

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