LCD projector settings (explanations please?)

Discussion in 'Projectors, Screens & Video Processors' started by bigalroz, Oct 26, 2001.

  1. bigalroz

    bigalroz
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    Having recently purchased a Sony VPL CX1 LCD projector and taking a peek at the Service menu, I have a few questions. I have been fiddling about with the RGB values to achieve a better picture (taking note of the original values first of course). I would like to know what Bias is and does? Should this be left alone or can tinkering with this also improve the picture ?

    Any info on the best way to calibrate the projector would be gratefully received also. Currently (not having VE or AVIA discs) I have the colour, contrast etc calibrated to best match DVD played my faithful old TV (RGB Scart). Is this a good way to calibrate it? I tried using the THX Optimode stuff but wasn't that impressed.

    P.S. I find this projector the bees knees for the money. The picture is amazing. Makes a big difference in my appreciation of my Sony 5.1 receiver too :)

    Cheers in advance guys!
     
  2. jrwood

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    I too have this fabulous projector, great introduction to Hcinema!. Anyway how did you get into the service menu?, what are the key combos! :)

    I believe people use filters (about 15 quid?) which help reduce blacks by 50% from reading http://www.thebigpicturedvd.com/vw10ht_faq.shtml not sure if this applies though to the baby sony projector?

    Thanks again!
    James
     
  3. bigalroz

    bigalroz
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    James,

    To get into the service menu press ENTER,ENTER,UP,DOWN,ENTER then UP when prompted if you want to enter service mode. The next time you enter the menus there will be some extra service type options.

    BUT PLEASE ANYONE CHANGING THE VALUES IN HERE NOTE THE ORIGINAL SETTINGS BEFORE CHANGING ANYTHING. AND DON'T CHANGE ANYTHING YOU DON'T KNOW ABOUT.

    Sorry James this warning is no directed at you, I'm sure your sensible enough to know this as are most members I guess. I just don't want anyone buggering up their lovely kit:)

    Alan.
     
  4. LV426

    LV426
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    Once in the service menu - check out the GAIN values for R, G, and B. If one of them (probably R) is significantly higher than the others, then the coloured filter idea will probably work for you. It relies on the supposition that there is some unused headroom in two of the three colours.
     
  5. jrwood

    jrwood
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    I`ll have a look in the service menu tonight :), and let others know whats in there. If the one of the colours has a much greater bias how does the filter work?, wont you lose clarity in the picture?. If it works then it sounds great as the CCR20 ? which most people use for 10HT is only about 20 pounds and apparently reduces blacks by 50% ?.

    Also would it fit the CX1 projector?, or is it a case of 'sticking' the filter to the projector!?.

    Thanks again!
    James
     
  6. LV426

    LV426
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    It's not the BIAS values you need to check - it's the GAIN values.

    The theory goes like this:

    If you place a filter in front of the lens, then it will have the effect of reducing the total amount of light output by the projector - and colouring it (for a red filter, it will colour it Pink).

    The effect on black is profound. The coloured tint is unnoticeable - but the reduced amount of light IS - very noticeable i.e. blacks get significantly blacker.

    So, having reduced the total light output - you get better blacks, but lighter colours are tinted (say, Pink). So, you compensate for the tint by raising the gain on the opposing colours (eg blue and green). This has the effect of restoring brightness and colour balance on non-black parts of the image. Net result - better contrast, similar or same overall brightness - but deeper blacks.

    As I said - it only works if your factory settings indicate that there is some spare headroom in two of the three colours' gain values. You use a filter corresponding to the highest gain value. If Red is highest, you use a red filter. The "R" in the filter code refers to red.

    I used a CC20R on my VW10. It cost £9 + £1.50 for delivery for a 85mm square gel filter, from www.formatt.co.uk

    Depending on the amount of headroom (and I don't know how to work it out other than by trial and error) you may want to use a different density filter. Some people have used CC30R and CC40R to good effect. But, if you find that the overall tint is so great that you have to REDUCE the gain on the brightest colour(eg Red) to get good balance (ie because one of the others is set to its maximum) - then you've used too strong a filter.
     
  7. jrwood

    jrwood
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    OK!, I just went into the service menu and it adds a few extra options to the menu. The last menu option which is'nt usually there specifiys the settings for 'LOW' and 'HIGH' which is obviously the presets for the colour temperature.

    Anyway the default setting for my VPL-CX1 is

    LOW: R=64 G=60 B=60
    HIGH: R=64 G=64 B=64

    Rom version is 1.02 - everyone else with the CX1 have the same?!

    Any ideas of any tweaks we could do with these?, the highest setting for each colour is 255. Perhaps having these at 128/128/128 would provide more vibrant colours?, what do you pro's think?. I presume with the default settings the idea of the filter is a no go ?

    James
     
  8. LV426

    LV426
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    From the values quoted, it looks like the internal optics and colour temperature of the Lamp make the projector evenly balanced. In which case, a colour filter probably won't help. However, I am surprised by the lowness of these settings, in relation to the theoretical maximum (64 vs 255). Are you SURE you are looking at GAIN and not BIAS values?
     
  9. jrwood

    jrwood
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    You cannot change the BIAS settings it seems. When you click on each of the colour temperatures and modify the RGB settings it says up the top GAIN and not BIAS.

    I changed the GAIN settings to 80,80,80 last night (80 contrast/55 brightness) and found that in dark scenes more detail could be seen and a more vivid picture with the brightness being lower blacks seemed better. However until I get some black felt (hopefully this week touch wood!) then you cant really get the optimum picture quality as light overspill detracts from the main picture imho at the moment on dark scenes.

    I tried 128,128,128 but this seemed too 'colourful' although maybe turning down the contrast/brightness more may of helped?. Again I will experiement and find the best settings once I find some felt!. I think it would be a good idea to get the AVIA or video essentials? DVD (which is the best one to get?) so that we can determine after calibrating the projector properly if the gain values should be near each other or not.

    James
     
  10. LV426

    LV426
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    If colour correction isn't an option (it appears not), and if there is headroom in the Gain values of all the colours, then another approach might be to use a Neutral Density (Grey) filter. This will uniformly dim the picture - which you can then compensate for by increasing the gains on all the colours. Effect - theoretically - is that blacks get darker (because of the filter) and brights stay the same because you have increased the gain.

    This presupposes that increasing gain values doesn't ALSO increase Bias (if not separately adjustable) ie that increasing Gain increases contrast - and not brighteness.
     
  11. jrwood

    jrwood
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    What grey filter do you recommend? (model #?), I will probably get it from www.jessops.co.uk (local stores near me so its easier..). When I changed the the GAIN values to 128,128,128 last night the colour was too much even for my grey screen 80,80,80 seemed much better than the default 64,64,64.

    When I changed the GAIN it didnt seem to affect the brightness whatsoever, the reason why I turned down the brightness to 55 was because now the colour was more vivid darker scenes seemed much better with shadows.

    thanks again
    James
     
  12. jrwood

    jrwood
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    bump! ;) :D :clown:
     
  13. LV426

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    OK, from what you describe, altering these colour values isn't altering the total gain of the picture - it's increasing the colour intensity. So the indication from your description is that these controls are having a similar effect to the COLOUR control on a TV - rather than the CONTRAST control (albeit three colours separately).

    All of which leads me to believe that, unless there is another control, elsewhere, that allows individual colour gain values to be changed (affecting both luminance AND chrominance) then there's little mileage in further "tweaking".

    Use of a Grey filter works at its best if, within the user or service menus, there is some headroom in the contrast ie you can increase the brightness of the bright parts to compensate for the effect of the filter. Otherwise, a grey (Neutral Density) filter will improve blacks, but at the expense of overall brightness. This may still be of benefit, however. As for which model, I have no idea. Talk to a camera shop. Try and find one that will let you swap for a different density if you find the one you chhoose has too much, or not enough, effect.
     
  14. jrwood

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    Well it is the gain which it is affecting, but I will ask a camera shop about it but I have a feeling they will look at me completely clueless....
     
  15. samwiley

    samwiley
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    This thread has been a god send - service menu = picture tweaking heaven!!

    James

    You get to the BIAS values by going to the same place that you find the GAIN R/G/B.

    If you move the cursor/highlight down past the B(lue) GAIN setting, the cursor goes back up to R(ed) but you're now at the BIAS settings for R/G/B.

    These are set at something like R:124, G:125, B:126 (can't remember if that's HIGH or LOW)


    Nigel

    Trouble is I don't really understand what they do except that GAIN seens to make the picture more coloured but leaves brightness unchanged, whereas BIAS seem to change both colour saturation AND brightness.

    Any tips on how best to use GAIN or BIAS or explanation on what changing them actually does?
     
  16. jrwood

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    Sam what Rom version is yours? mine is 1.02 as my previous post stated

    I agree that this menu is a hidden bonanza of secrets!, I must admit having gain at 80,80,80 gives a more vibrant picture especially for dark scenes.

    James
     
  17. LV426

    LV426
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    AFAIK (and it may differ on your projector):

    It's easier to describe these thigs as if you were adjusting all three colours together. If you do, then.....

    BIAS determines what signal levels the projector interprets as black. Set it too low, and things that should be dark grey start being reproduced as black - i.e., you loose detail in dark areas. Set it too high, and blacks get less dark ie you loose contrast.

    GAIN determines what signal levels the projector interprets as white. Set too high, and things that should be nearly (but not quite) fully white start being reproduced as white i.e., you loose detail in bright areas. Set too low, and whites start getting darker ie you loose contrast.

    Clearly with three colurs to adjust, these effects can be applied (or removed) separately from each colour.

    So, the trick is, to set gains as high as they will go, without loosing bright detail, and bias as low as they will go without loosing dark detail. And ensure that the three colour values are set such that you don't end up with an unwanted tint, either across the whole picture, or just in the bright areas.
     
  18. Cliff

    Cliff
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    Bias and Gain.

    You need to use a grey scale for this - black to white if you have it on a disk.

    Brief explanation.

    The bias should be set up so that at a very low level ie hardly any drive to the lcd panel the overall colour is black or grey. eg the low level starting point for each colour is the same. So the dark end of the grey scale should be grey/black and not have a colour bias.

    The Gain settings should be adjusted so that the rgb colours track from black to grey to peak white. The Gains affect the whites.

    Just beware of one colour gain being too high as this will limit before the others and then the other colours will then overtake and give you a shift in colour

    Clear as mud?
    Happy TWEEKING

    CLIFF
     
  19. Gordon @ Convergent AV

    Gordon @ Convergent AV
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    Gain is used to adjust greyscale of the high brightness parts of the image and Bias affects the low part. They are interactive to some degree.

    To do this properly you need a video analyser and a test discs or source with low and high IRE grey window patterns.

    If you have AVIA or V.E. then put up a 70ire pattern and adjust gain then put up a 40 ire one and do Bias. Switch back and forth until you are happy. Then put up some material and see how it all looks.

    You should adjust brightness and contrast to suitable levels before doing this then check they are OK after. If you change them afterwards go back and check the greyscale again.

    Gordon
     
  20. Mr.D

    Mr.D
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    I tend to use 20IRE and an 80IRE but don't suppose it matters. ( and I'll verify a 50IRE reaches 6500K once I've balanced for the other two : it inevitably does) I also note the initial luminence value ( after setting correctly) before adjusting for both patches: once I'm happy with the grayscale tracking I 'll raise or lower all the RGB values for either gain or bias by the same amount to restore the original luminace aims.

    This shouldn't upset the colour balance unless you have to go crazy. I tend to drop individual RGB values to reach the 6500K aim rather than raise any : then I'll lift them all to re-establish the original luminance aim . ( some sets only allow adjustment of red and green which is enough but means upping values to lower the overall colour temp in most cases)

    This should guarantee you don't get any of the primaries fighting against each other.

    I'm assuming on a panel display that the values don't equate to real voltages but concatenate with each other so you won't get any fighting anyway but could be wrong.
     

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