1. Join Now

    AVForums.com uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

VW10 bias puzzzle

Discussion in 'Projectors, Screens & Video Processors' started by loftfuton, Aug 17, 2004.

  1. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    Hi

    Researching SMART Calibration comments in the forum before buying, then had a look at my bias settings on the VW10. I get two different sets of figures depending on what projector input I look at - A or B.

    INPUT A bias settings are R79, G89, B91 and remain the same for every colour temperature.

    INPUT B bias settings are different to INPUT A, and unlike A, change with colour temperature - between R103, G89, B106 and R104, G89, B102.

    As I bought the pj second hand I am assuming the previous owner has been tweaking - I would have expected that there should be no difference in the bias figures between the two inputs - am I correct in this assumption ???

    If so anyone any idea what input settings are likely to be the correct ones ?? - would Bias be expected to vary with colour temperature as with my INPUT B ???

    Thanks for your help

    Harry
     
  2. RTFM

    RTFM
    Active Member

    Joined:
    Mar 6, 2003
    Messages:
    1,014
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    38
    Location:
    Horsham, West Sussex
    Ratings:
    +17
    Bias and Gain are what change the colour temperature which can be configured in the High/Low and HBM settings.
    If both inputs A&B are both set to the same col. temp setting then they will share the same gain and bias settings.

    Jeff
     
  3. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    Jeff

    Thanks for your reply, which has opened another can of worms for me.

    I did as you suggested - looked at the same colour temperature in A and B and compared figures. They were identical for both Gain and Bias. When I looked at different colour temperatures, Bias figures always remained the same, but the Gain figures changed, and the changes were mirrored for both A and B inputs.

    This was done with no sources fed to the inputs. As soon as I switched on the DVD player, which is feeding INPUT A, both the Gain and Bias figures changed dramatically - I was looking at Low colour temperature.
    Similarly when the source for INPUT B was switched on - Freeview receiver- the figures changed for that input.

    This confuses me because the The SMART Calibration is based around the Low colour temp Gain and Bias readings, which I understand to be factory adjusted to give a certain calibrated 'white' - but what figures do you use, the ones you get when the source input is switched on or off ??

    I've probably missed something really obvious here so apologies beforehand if I have !!

    Harry
     
  4. RTFM

    RTFM
    Active Member

    Joined:
    Mar 6, 2003
    Messages:
    1,014
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    38
    Location:
    Horsham, West Sussex
    Ratings:
    +17
    Harry,

    I don't have a VW10 any more so can't give you any figures.

    There's the unofficial VW10 w/s at: www.thebigpicturedvd.com/vw10ht_faq.shtml
    where you should find some useful info.

    Hope it helps

    Jeff
     
  5. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    Jeff

    Had a look at that thanks, but it did'nt clarify things for me - will post this new problem as a new thread.

    Harry
     
  6. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    This issue arose at the end of another thread but I wanted to open it up for 'wider consultation' - hope this hasn't broken any Forum rules.

    Was talking about calibrating my Sony VW10 with SMART, and the issue of using the Low colour temp setting as a reference point.

    With no sources fed to the inputs of the projector, the Gain and Bias figures for Low were identical for both INPUT A and INPUT B. When I looked at different colour temperatures, Bias figures never changed, but the Gain figures did, and the changes were mirrored for both A and B inputs - so be it.

    As I said this was done with no sources fed to the inputs, and looking in particular at the Low colour temp figures. As soon as I switched on the DVD player, which is feeding INPUT A, both the Gain and Bias figures changed dramatically. Similarly when the source for INPUT B was switched on - Freeview receiver- the figures changed for that input.

    This confuses me because the The SMART Calibration is based around the Low colour temp Gain and Bias readings, which I understand to be factory adjusted to give a certain calibrated 'white' - but what figures do you use, the ones you get when the source input is switched on or off ??

    Gratefull for any comments - even the ones that say I'm an idiot and have totally missed the point !!

    Harry
     
  7. Kramer

    Kramer
    Guest

    Products Owned:
    0
    Products Wanted:
    0
    Ratings:
    +0
    No real need for a separate thread so I've merged them ;).

    Off to bed now but I'll have a look at your question(s) tomorrow - might be able to help.

    :smoke:
     
  8. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    Kramer

    Any thoughts yet ???

    Harry
     
  9. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    Hi, I don't have a projector and I've only come across your thread as a matter of accident however perhaps as a broadcasting engineer of many years service I can give you a few pointers that might explain a few things? Talking about colourimetry in general, all colour tv systems (pal NTSC etc) have to have some sort of reference white otherwise who's to say what's white ! - your white shirt is white to you but I might consider it to be a bluey white - another person might say 'no, its a bit yellow - my shirt is white' and so on and so on. In the UK the standard reference white in day to day use in tv is called Illuminant D6500 (shortened usually to illuminant D). What's the 6500 ? - its the temperature (in degree kelvin) of a piece of special wire heated to that temperature - as I'm sure you know as you heat a piece of metal up is goes from dark red to cherry red then 'white hot' etc - pretty easy concept to grasp. Why did we choose that temperature rather than say 7000K ? well believe it or not that colour temperature is supposed to be the equivalent of daylight on a bright spring day around noon in Washington DC - sounds as though I'm pulling your leg - but I'm not, it really is that ! (by the way as an aside, in the very early days of colour tv in this country the reference was illuminant D6000 - a slightly warmer colour (the higher the colour temperature the bluer the light) - but the engineers looked at it after a while and decided to go with 6500 instead (a bit of history for the anoraks there !). In theory when your projector is being line up by the manufacturer that is what they should be adjusting the white output to be - however in practice they probably set it up to be something that looks nice and gives reasonable flesh tones. You say that as you change the colour temperatures the bias figures stayed the same but that the gain figures changed - that would be as expected. Think of a conventional CRT - 3 colour guns. How do we set up the bias and gains ? well bias concerns the drive to the guns when the input signal is black - sometimes referred to also as 'Cut off' We adjust the individual bias of each gun such that the picture on the crt is black. We then inject a signal corresponding to white - we then adjust the gains of the individual guns so that the 'white' we see on the crt is what we want (ie, illuminant D6500). We could set the gains to be any 'white' - remember what I've said above - who's to say what's white ? So, think about it, no matter what colour temperature you are trying to set the crt up to the BIAS set up is when the CRT or projector is giving out BLACK which is the same NO MATTER what the colour temperature is because that's the 'white' part of the adjustment. Same principle with a Plasma/LCD screen or projector. As to why the gains change when you select different sources - well I have to admit I'm on sticky ground here, well whatever 'white' the projector manufacturer has decided to make the screen to be when its fed with a white signal should be the same whatever the source - ie, freeview box or dvd player etc. The only thing that MIGHT change is that there is a difference in the agreed output of these boxes, ie there is no standard. There is another possibilty - I don't know what all the 'SMART' stuff is so forgive me if I speak out of ignorance. I'm guessing that maybe its some kind of internal test signal that is projected onto the screen when in the SMART mode ? I presume either you manually (or the kit itself automatically) adjusts the picture to be your standard 'White'. This test signal would be injected at the start of the signal chain (as near as practical to the input connections) to take into account any circuit or component variations in the signal path. If you perform this SMART test on the A and B inputs then if there were minor variations in the signal path then you might get minor variations in the bias and gain figures. If you then come out of SMART mode (?) and then connect up the external equipment then the signals generated from the external equipment are likely to be different from those generated by the internal SMART generator and that would explain why the gain and bias figures alter - to take this into account. You could prove this by swapping over the Freeview/DVD signals and seeing if the gain/bias signals swapped as well (probably not). Well as I say I don't know anything about projectors but I do know too much about tv's !! (and the bit about Washington DC is absolutley correct - look it up on the internet if you don't believe me) regards, yt.
     
  10. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    yt

    Thanks very much for your considered reply. It has clarified for me the purposes of the gain and bias measurements, and even had a bit of history thrown in !!

    SMART III is actually a system for calibrating video projectors. It's "based on a commercial light meter that allows accurate measurements of light intensity over a wide range of light intensities - the dynamic range of the meter is 2 million to 1. Needless to say, this allows accurate measurement of contrast ratios for virtually any projector available today and for the foreseeable future.To further improve accuracy, each light meter is individually calibrated immediately prior to shipment".

    "This bundle includes everything you'll need to calibrate your projector. You'll receive the light meter, specially designed Red, Green and Blue filters that are used in the calibration process, and the SMART III Software"....so the blurb says.

    An inherent problem with my type of Sony projector is the bulb light which i understand tends to be on the green side. By fitting a red colour correction filter to the lens, and then re-doing a white balance this is supposed to have the dual effect of correcting this and increasing the contrast ratio of the picture.

    The 'Low' colour temp setting of the projector (one of about 6 settings that have been factory installed) is supposed to coorespond to the D6500 temperature, and the idea of SMART is to help get you back to that balance after adding the colour correction filter.

    This all seemed fine and dandy until I had a look at the Gain and Bias figures, and noticed how they changed dramatically - not just a minor variation - after switching on the dvd player. Like yourself I did not think these would have changed as they are based on measurements internal to the projector. So what figures do you use for the D6500 reference?? around which the rest of the calibration is based.


    There is my problem, and I am assuming anyone elses problem who has this projector and who wants to do a SMART calibration - unless mine is faulty in some way, which could be proved by someone else with a Sony VW10 checking their figures before and after switching on the source device, and posting their results.

    Thanks once again for taking the time to post that helpfull reply.

    Harry
     
  11. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    Hi Harry - well I'm glad my D6500 figure tied up with your calibration procedure. From your description the SMART system seems a very fair way of calibrating the colour temperature of the light output of the projector. We have a similar system when setting up professional CRT monitors (Sony, Barco etc) but for us it is even easier. We plug the 'light meter' into the front of the monitor and stick it with 'suckers' on the front of the crt - then press 'go' in one of the set up menus. The light meter has three (RGB) pickups inside it so we do not have to manually place gels in front of the meter (but of course it doesn't come cheap !). Having pressed 'go' we see the monitor automatically adjusting the gun biases and gains to give us the desired colour temp AND light output - remember one light bulb in your ceiling gives a specific colour temp, if you switch on another bulb next to the first one the colour temperature remains the same (its the same bulb after all) but the light levels increase. With ref to your problem (and as I say I know not a lot about projectors) what's the point of putting a red filter in front of the lens if you then 'calibrate out' the effect of the 'redness' with the SMART system ? when you perform the calibration where is the test signal generated that is displayed on the output of the projector ? (is the SMART box a signal generator as well). It seems as though you are saying that the projector detects that you have switched on an external device and then decides to alter the Gain/bias settings as a result ? However, there is a danger here that I am leading you down the wrong direction since I don't know anything about this kit so Ii will offer no further dictractions/thoughts - good luck. regards, yt
     
  12. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    13,998
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,802
    yT: Smart doesn't calibrate to D65. It calibrates to get consistent ratio's of RGB relative to first set of measurements, at least I think that's what the poster is suggesting. That is why he is keen to find out which temp setting he should start from. My own findings are that LOW is often closest to 6500K but is not usually close to D65 which is not the same thing as you have said.

    The device you use is no doubt a tristimulus colour analyser...not a light meter.

    BIAS in the Sony doesn't act the way you are used to with CRT devices. the adjustment you talk about sounds like G2. BIAS on a Sony LCD is an adjusmtent to allow fine changes to the greyscale RGB levels in the dark part of the image an d it is interactive with the DRIVE/GAIN RGB values which have greatest affect on bright part of the image.

    Gordon
     
  13. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    Thank you Gordon, as I say I know nothing about projectors and I cannot comment on that topic any further - my comments were more concerned with aspects of colour temperature as applied to colour television systems. Yes we are using a 3 colour analyser to line up our monitors (either manually or automatically) As you will be aware it has three independent light sensors each with a colour filter in front of it to separate out the luminance levels of each colour. In that sense it is a unit with 3 independent light meters - the output of each corresponding to each colour in turn (I did not think referring to it as a tristimulus colour analyser would be helpful to Harry !)

    'Bias' for the Sony LCD sounds like it is the same for a crt, it will affect the colour balance of the screen in dark areas (like a crt) and since we are 'lifting' or 'reducing' the baseline drive to the display then as you say it will affect the gains as well. Since the bias/gain on the lcd panel seems to behave in the same way as in a crt I guess that's why Sony have chosen to use classic 'CRT' type nomenclature to describe the operational effects of these controls. Why does the LCD projector need to have different 'white' operational settings ? is it to allow it to cope with different ambient light conditions ? perhaps to cope with different sources of originating material (ntsc DVDs etc) which will have a different reference white than with European PAL regards, yt.
     
  14. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    13,998
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,802
    They have different settings because they can.

    They tend to have a 9300K(PROBABLY nearer 12000) FOR PC data use and because Japan tends to use this temperature for white as they think it looks nice............mmm...

    5400K or less is often a choice on PJ's as it's supposed to be the white balance used for projecting video that will recorded during broadcasts (I think).

    Occassionally you get a 6500K setting but alot of these are far too green and are not D65. This is done as it measures better in their stupid contrast specs.

    Accurate picture reproduction is usually not a criteria for many PJ manufacturers I think.....although there are some who then give you the controls to do it yourself and others who do actually have a go out the box.

    Gordon
     
  15. red16v

    red16v
    Active Member

    Joined:
    Aug 20, 2004
    Messages:
    552
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    18
    Ratings:
    +5
    "Accurate picture reproduction is usually not a criteria for many PJ manufacturers" - ah, I thought as much.

    But then again its true of many conventional televisions -I have yet to see a domestic television that has anything like ebu phosphors on its crt. I think (like some projector manufacturers) that they devise a phosphor formula that gives (to them) a a 'nice' looking picture. I suppose at least it gives the consumer a 'choice' (and something to argue about on these forums !! regards, yt.
     
  16. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    Chaps

    Interesting discussion, and all very well and good, but its not getting the baby's face washed. There must be a 10HT owner out there who could check their gain and bias figures of either INPUT A or B for me before and after switching on their signal device whatever it may be - dvd player, sat receiver etc - to see if they also get a big change in those Gain and Bias figures !!?!!, then I can go to Enhanced HT or Steve Smallcombe for their comments.

    Gordon, youv'e poked around a few 10HT's in your time - can you explain this ??

    Harry
     
  17. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    13,998
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,802
    Never looked at those menu's with no device plugged in or turned on. I would suggest you should be using figures you see when a signal is applied.

    Gordon
     
  18. loftfuton

    loftfuton
    Standard Member

    Joined:
    Feb 4, 2003
    Messages:
    93
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    8
    Location:
    BELFAST
    Ratings:
    +2
    So what would generate the change and on what are the new figures based I wonder ??- that is of course providing I do not have a fault - which I am still trying to get to the bottom of.

    Obviousley Sony cannot possibly programme a range of gain and bias figures to cover every type of device that is likely to be plugged into their pj,s.

    Harry
     
  19. Gordon @ Convergent AV

    Gordon @ Convergent AV
    Distinguished Member AVForums Sponsor

    Joined:
    Jul 13, 2000
    Messages:
    13,998
    Products Owned:
    0
    Products Wanted:
    0
    Trophy Points:
    166
    Location:
    Living in Surrey, covering UK!
    Ratings:
    +2,802
    It's likely to change based on signal type, resolution and scan rate....ie 480i Component may give different offsets compared to PAL via s-video.....

    Gordon
     

Share This Page

Loading...