too bright!

Scott,


It could be many different things:


1) Contrast/Brightness set incorrectly at the source - most likely the case if this is an HTPC (what is the source anyway?). If your source is HTPC, search the HTPC forum for the correct settings to use for Brightness/Contrast/Hue/etc depending on what video card you use.

2) Contrast/Brightness set incorrectly on the scaler... (are you using a set-top DVD player with an external scaler? Does it or the DVD player have any B/C settings?).

3) Do you use an external switching box of any sort in the signal path? Some Extron boxes have settings that can be tweaked (incorrectly).

3) G2 settings incorrectly set in the 808s. Search the forum here for how to set this properly, though you should make sure everything upstream is correctly set first.


I have no problems with the brightness of this movie... the only problems I have are the same source related problems other people have: The use of Edge-Enhancement and a generally soft, murky, muted image at times (generally inconsistent image). Not reference quality by any means.


Kal

I am using a non Progressive scan DVD player and no line doubler/scaler. I am also not using a HTPC, needless to say.

The signal goes from the DVD to my Lexicon MC-1 to the PJ. I doubt there is a video setting that can be accessed within the Lex.


The Barco was used for rentals and has 1250 hours, is it possible that the G2 was set for displaying graphics only?


I will do the search on G2 before I delve into that.


Thanks


Scott

Your problem seems that your projector gamma doesn't match the gamma precompensation of the DVD.


Gamma is a y=x^gamma function to correct the non linearity of the CRT luminosity.

DVD are precompensed with a gamma of 2.2 (I'm not 100% percent sure of this figure).


If you cannot change this parameter at your projector or at your source : there is no solution, darks will be too dark or whites will be too whites.


I have a Sony 1031 and I mesured a gamma of 2.9 with a computer chart. So the theory says I have to correct the gamma about 2.9/2.2=1.3 And without doing it I have the same problem as yours.


Gamma is a key parameter for a good looking picture.

(Gamma is not G2, brightness, picture, contrast, black level or drive).

Quote:
Interesting! Were did you find this computer chart?


Some extra info for people unfamiliar with the term 'gamma' and where it fits in with Brightness/Contrast/Tint/Hue...

Gamma Correction:

An adjustment to the light intensity of a scanner, monitor or printer. It generally refers to the adjustment of the brightness of a display screen in order to compensate for a CRT's irregularity. A gamma correction plot is a curve, not a straight line as is the standard brightness control. Gamma correction is also used to make the monitor display images more closely in appearance with the laser printer that creates the output.


This dictionnary definition actually explains it better:

A correction to the contrast of images and displays, performed by either software or hardware, and designed to correct for the fact that the intensity displayed on a cathode-ray tube is not linearly related to the input voltage.


FYI - Many video card drivers have built-in gamma correction, so it's possible to play with the gamma settings if you're using an HTPC. (I believe the ATI Radeon drivers have gamma adjusments, while the NVidia GeForce line of drivers do not).


Kal

Guys,


There are some THX test screens on this DVD - one of which is used to set black level (the one with the THX logo with the blacker-then-black border) and another with 4 white boxes of slightly different brightness.


Do you see the 4 boxes are distinct shades of white? If notyour whites are being crushed (either by the source, or maybe the contrast is set too high on the projector).


Do you still (slightly) see the blacker-then-black border on the THX logo test page? If not, then your brightness is set too low. If the border is much darker then the background then the brightness is set too high.


This DVD has all you really need to set your brightness/contrast properly *ASSUMING* your source isn't screwing it up by crushing the whites or not passing true blacks. As someone mentioned, if your source is messing up the signal, there's nothing you can do to fix it at the projector. Your source should be feeding you a true 0-100 IRE. (roughly 7-700mV).

If your source is an HTPC, then all this has been 'scoped out and there are known values for contrast/brightness/hue/saturation based on what type of video card you use. Check out the HTPC forum for more info.


Kal

About the gamma chart:


Here:
http://www.aim-dtp.net/

System calibration | monitor calibration


You can find the monitor calibration chart:
http://www.aim-dtp.net/aim/download/mccp_v1.4.gif


Be careful this chart should not be resized in anyway to work.


Here is the way to test your gamma:

- Reset the color calibration of your video card.

- Display the chart without resizing.

- Choose a reference gray, for example 37.3.


A:

- Adjust the brightness of your projector (not of the video card as it can crush the whites or blacks) so the plain gray on the left match the interlaced gray. (You have to be far away or close the eyes a little bit so you don't see the interlacement anymore).

- If the grays darkest as your reference (

Going back to basics on this, it could simply be termination!


If the video signal is not terminated with 75 Ohms, the picture will be way too bright - and give exactly the image you describe.


I'm not sure on what is on your PJ, but there may be a 'loop-thru' connection (particularly if you are running composite video) - this should have a 75 Ohm terminator fitted. There may also be a switched marked Term or 75R or some such (often mounted between the connectors) that switches an internal resisitor in and out.


Have a look at this before playing with any internal adjustments!



Hope this helps,


Richard Ansell

Snell & Wilcox

Scott,


in my opinion, the problem could be:


1) the fact that you setted "boost mode" on the 808-s (from the menu), in this case the pj works with a very high contrast (and it will reduce the timelife of the tubes);


2) the fact that you're using the composite signal, it is not only the worst kind of input signal, in terms of picture quality, but it normally requires a very different contrast/brightness control than a normal RGB (whatever sync mode) input;


3) the 75 hom resistor termination, as Richard wrote;


4) a wrong setting of the gamma and color parameters (specially G2), in this case, if you have had an RGB cable you could have checked immediatly it...


Start checking if you correctly setted "normal mode" in the image menu.



just the my opinion.


Romano

wow all this help, and me with a brain the size of a pea!




well I am using 30 feet of SVideo cable to start with...


The PJ is set to economy, I have tried normal and it appears the same, I am not using boost...


I am forced for the time being to pass the signal through the Lex, though I can test it by moving the DVD closer and run it right into the PJ.


I will look for the switch on the back, there was one...I just can't remember what it said. Tonight when it gets dark...


Yes the scenes in the desert on phantom menace are real bright...I will try setting the brightness and contrast with the THX stuff on the dvd.


I am still a few months away from a HTPC, is there anyone in Toronto who wants to bring theirs over to help me identify the problem? I have a fridge full of beer!


Thanks for all the advise guys...

Scott

I adjusted the G2 of my Barco 808s, I only had to turn the pot 1-2 degrees at most.

I also adjusted the green to 50% it was at 68% for some reason...

I also removed the Lex from the signal path...


well, when its bright at least now its not green and bright.



I tried to use the THX white square on the Phantom menace DVD, but still can only see one big square, not 4 (8?) multi shaded squares.

I will put my DVD right next to the PJ tonight and use a good quality (and shorter) SVideo cable.


Any more ideas?


Thanks

Scott

Richard wrote...

---------------------cut----------------------

If the video signal is not terminated with 75 Ohms, the picture will be way too bright - and give exactly the image you describe.

Richard Ansell

Snell & Wilcox

---------------------cut----------------------

Well Richard, you were right. I found the switch for 75 ohm in the off position. I switched it and voilla. great colour and contrast.


It seems odd that the switch should be in the "on" position for a SVideo input though.



Thanks

Scott