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Setting contrast

Discussion in 'Projectors, Screens & Video Processors' started by Nebby, Oct 28, 2004.

  1. Nebby

    Nebby
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    Hi all

    I'm looking for any tips, guidance or tricks of the trade on setting contrast levels.

    I have a Seleco SVP 320 Plus and have been able to set Peaking (50), Hue (50), Colour (73), and Brightness (45) using my Digital Video Essentials disc and the THX optimiser.

    Setting Contrast is proving to be a little bit more problematic, even with the help of the above.

    For example, I don't see any 'blooming' when adjusting contrast, nor line distortion when using the needle pulse test. However, my DVE disc tells me that this not unusual with certain CRT projectors.

    At the moment Contrast is set at 45 - looks great on certain movies, average on some, and downright dingy on others!!!

    So, has anyone got any good tips on setting Contrast? Any advice on what to look for on screen when adjustment is being made, recommended discs / scenes to work from, or any ratios (in relation to brightness) that work as a rule of thumb?

    Also, any advice on what effect COMB FILTER and GAMMA ADJUST might have on contrast would be most welcome.

    Thanks in advance, as always.

    Nebby.
     
  2. Chris Frost

    Chris Frost
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    Hi Nebby,
    First - check your DVD player. Some have picture control settings. You may need to reset these first before adjusting the projector.

    Next go to the Colour Adjustments menu in AVIA and select one of the colour bars patterns from the Standard Colour Bars menu.

    Look to the bottom left to see a white box with two vertical stripes moving left and right. Adjust the Contrast control until the right hand stripe just merges with the white background. Memorise this setting. It will apply to your NTSC films.

    Repeat the same type of adjustment with whatever PAL test dics you have and memorise the setting.

    Final tip: You'll end up with different values for the picture control settings in a bright room compared to a darker room. THat's quite correct, but it does mean you can have a one-setting-fits-all solution. Also, film, video and TV broadcast will have different picture levels too. Be prepared to experiment a little.

    Regards
     

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  3. Chris Frost

    Chris Frost
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    Comb filter - no effect on contrast. It improves colour separation with composite video and RF signals.

    Gamma - the effect of altering gamma is you'll see more detail from shadow areas which sounds a bit like what brightness does. What you're actually altering is the response of the display to its input signal between the black point (fixed by brightness control) and the white point (fixed by contrast). Too much gamma makes the shadows look grey and the colours look washed out. Try 15 as a setting.

    Regards
     
  4. Nebby

    Nebby
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    Hi Chris

    Thanks for the above, particularly the notes on gamma and comb filter.

    I don't have the AVIA disc...do you know if the DVE disc has something similar to the AVIA Colour Adjustments menu you mention...(I've given it a quick scan, but didn't spot anything)...or should I splash out on the AVIA disc. I see a lot of posts rate it over DVE.

    Cheers, Nebby
     
  5. Chris Frost

    Chris Frost
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    Ah...yes, you said that :blush: I really must learn to read :laugh:

    DVE has some similar patterns you can use. The test card in the Picture Resolution menu > SMPTE RP1.33 (Title 13, Chapter 02) or any of the Snell & Wilcox zone plate test patterns will do. They're the ones with the moving ball.

    Adjust until the slightly darker white square merges with the background, then back the contrast off a little until the centre square just becomes visible again.

    As for DVE vs AVIA...

    on the plus side for DVD there is both a PAL and NTSC version. AVIA is only NTSC. I think DVE has the technical edge over AVI in terms of reference accuracy of the video test patterns - but I've no hard and fast evidence to support that. It's just that DVE is such an ar*e to navigate.

    Should you buy AVIA? For the odd tweak to your system I'd say it isn't worth it, especially if you watch mostly PAL. However, if a cheap copy comes up on the forum then grab it. But I want you, AVIA will spoil you and DVE will probably gather dust.

    Regards
     
  6. Nebby

    Nebby
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    Once again, cheers Chris!

    Although I wasn't able to see much of a difference when adjusting my contrast down (even at a zero contrast setting I could still see the little centre square), I've dropped my setting down from 45 to 33, which seems to have made a difference. This, coupled with the new gamma setting you recommended, seems to work really well for most of my PAL discs.

    It's interesting how discs vary - the fifth element, armageddon and spider-man all look fantastic, whereas titles such as jurasic park and the thin red line still look a little gloomy. Ahh, the vagaries of dvd!

    Anyway, on to my next question (don't you just love us newbies!!!)...

    You suggested that I will need to create different picture settings for both my PAL and NTSC discs.

    I'm having real trouble playing back R1 and R3 discs at the moment - but only when using my component cables. I'm getting horizontal 'streaking' across the screen, plus the picture fades from dark to light every now and then. This means I can only watch NTSC discs using S-VHS.

    The amount of 'streaking' seems to vary from disc to disc - seabiscuit just fades from dark to light, however black hawk down is completely un-watchable.

    PAL discs work fine with the component cables - although I have noticed a blue 'shaddow' that runs horizontally across the screen...but only when navigating the Star Wars (Episode 1 and 2) menu screens! For example, if I highlight scene selection or language setup, a fuzzy blue bar appears behind the menu heading I've highlighted. Switch to S-VHS and it disappears.

    I'm using the right memory settings (i.e. PAL vs NTSC)...either way, the Seleco STD select gizmo auto detects which setting I should use.

    My DVD player (Pioneer DV-353) is multi-region, so it should be able to handle NTSC.

    The cables I'm using cost over £150 - so I'd expect them to be good quality. And besides, if they were 'faulty' in some way, surely I wouldn't be able to view my PAL discs...or am I demonstrating my complete lack of understanding on the differences between PAL and NTSC?

    Any advice would be most welcome.

    Thanks (again), Nebby
     
  7. Chris Frost

    Chris Frost
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    You're going the wrong way!! :laugh:

    INCREASE the contrast until the two squares become the same brightness, then reduce contrast slowly until they become two different shades. I'd expect you to end up with contrast setting somewhere between 55 and 75 depending on room lighting , screen gain, age of projector, etc, etc,

    Before you make the contrast adjustment, put the projector into Install Mode and go in to the SetUp menu. Check that Adaptive Black is switched ON. Then go back to the DVE disc and set the Brightness level and Contrast, Colour etc

    That should sort out JP and Thin Red Line for those scenes that should look punchy.

    PAL and NTSC are different TV formats, so they need different picture settings.

    If your projector is set up correctly there should be at least 4 convergence memories set in the Memory Manager. There should be two for PAL (one for 16:9 and one for 4:3 & Letterbox) and two for NTSC (16:9 and 4:3/LB).

    Each of these four memories can hold a unique set of values for Bri, Cont, Clr, Pk, and Hue for NTSC only

    When playing a PAL disc your projector senses the difference between PAL and NTSC and then selects the first PAL memory in the list. It's then up to you to select the correct aspect ratio - wide or 4:3 if both are stored. [ Tip: the projector will default to widescreen if you put the W memories higher in the list than the N memories ]

    The streaking could be caused by any number of things. These could include the convergence controls being set past recommended limits, colour setting too high, incorrect impedance of the cable, using 50 Ohm BNC adapters instead of 75 Ohm ones, a problem with the component board, some issue with the component out of the DVD player. It's very difficult to make a diagnosis without seeing the actual machine.

    I'd suggest you try to eliminate as many potential causes as possible. Start with the simple stuff like rechecking the set up of the projector and DVD. If you did the convergence yourself then you'll know if any of the convergence controls are set near their limits. They shouldn't be, it usually means something more fundamental hasn't been adjusted correctly -usually it's the lens angle. Try moving the DVD close to the projector and substituting the component cable with 3 shorter composite cables. Visit a Maplins store and buy some 75 Ohm BNC adapters. Borrow a friends DVD player and try component from that.

    Let me know how you get on.

    Regards
     
  8. Nebby

    Nebby
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    If this little exercise has taught me anything, it's (1) be patient and (2) talk to an expert! :thumbsup:

    Double checked everything this afternoon (oh the joys of working from home!), from a spare set of cables to my old dvd player....but still seeing streaking across the screen...

    I then went through all the basic calibration steps, double checking my set-up was ok....but STILL streaking...

    ...and then came the breakthrough....I decided to check to see if the problem affected all of my R1 NTSC discs...it didn't!

    ...started to play around (sorry adjust) the PJ's picture settings and bingo...it was the Y/C Delay that was causing the problem.

    I'd set this using my PAL Digital Video Essentials disc in the past...but hadn't done so for NTSC...!!!!

    Am now going to spend the next 15 minutes using my NTSC copy of Near Dark, which includes THX Optimizer. Happy days!!!

    Thanks again for all your help...and for pointing me in the right direction.

    Nebby
     

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