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Avia Needle Pulse Pattern, What to Look for?


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4 replies to this topic

#1 of 5 KenRen

KenRen

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Posted June 13 2003 - 12:10 AM

All,

I have been trying to use Avia to perform the video calibration on a pair of Pioneer 64" HDTVs (one mine, one a friends).

The first test pattern, the needle pulse thingy, gets us eveytime. What are we looking for on rear projection TV of this size?

On a scale of -30 to +30, we have to go down to about -15/-18 to get the verticle lines straight. But, then the bottom portion doesn't look very white and the brightness setting is just too low when we finished the cal at this level and go to regular viewing. (Though we can get the black level just right even in this mode.)

We look at the steps in the upper half, but they do not appear to bloom even at max contrast. But, the vertical lines are definitely bent at setting of +10 and above.

The rest of the pattern tests we have no problem with.

Are we missing something here? Do we go for white and forget the lines? For rear projection HDTVs do we need to look at something else?

We can both invoke a "dark enhanced" mode on our DVD players.


Thanks,
KenRen

#2 of 5 KenRen

KenRen

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Posted June 14 2003 - 01:00 AM

I'm calibrating both sets with Avia this weekend. Can you hear me now? Can you hear me now? Can you hear me now?

Help!

#3 of 5 Allan Jayne

Allan Jayne

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Posted June 14 2003 - 01:10 AM

There are three criteria for the white level (contrast) control. Choose the lowest contrast setting you get from the three.

1. Screen burn

2. TV power supply (needle bend)

3. Phosphor overload (blooming)

If you don't see blooming, you are within the desirable limits for #3 and don't have to worry about it.

Some TV sets won't give a straight line for #2 because the power supply isn't well enough regulated from the start. You will have to pick a contrast setting where the line is not too badly bent and live with it.

For screen burn concerns, I just suggest trying to keep the contrast below 1/3 (-10 on a -30 to +30 scale) for a projection TV and below 1/2 for a direct view TV. There is a measurement that experts use that requires a light meter, but by the time you get enough brightness to satisfy the meter, you are at the point where you have to be ever vigilant to not let logos and MUTE and other bright stationary things stay on the screen.

Darken the room a little and the maximum white that didn't look so white using a lower contrast setting will look better.

Video hints:
http://members.aol.c...ynejr/video.htm
.

#4 of 5 Allan Jayne

Allan Jayne

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Posted June 14 2003 - 01:10 AM

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#5 of 5 Jeremy Anderson

Jeremy Anderson

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Posted June 14 2003 - 04:54 AM

I recommend ignoring the needle pulses pattern for RPTV's unless you're just testing for power supply sufficiency or to find the point of blooming. I calibrate contrast and brightness this way:

If the DVD player has a black enhance setting, that is to set the lowest black output. 7.5 IRE is the broadcast standard, but progressive players output 0 IRE as the lowest black. If your player has an option, set it to the lower setting before calibrating. Also, have your room lighting the way it is when you watch movies before calibrating.

Guy Kuo (creator of Avia) has said that the contrast test on Avia is to find the maximum allowable setting, NOT the optimal setting. Bring up a 100 IRE window in Avia's advanced patterns. Turn contrast all the way down. Then, turn contrast up just enough for the 100 IRE window to look pure white and not gray. This represents the brightest white you will have displayed on the screen, and will help prevent burn-in. In other words, if this screen is making you squint, it's too damn bright!

Once you have this set, bring up a 10 IRE window. Adjust brightness down until the 10 IRE window disappears. Then bump it up until you can just barely see the 10 IRE window.

After that, do the other settings and you should have a pretty sweet picture. It might seem a bit dark at first because most people are used to torch mode, but this will bring out detail and extend the life of your TV.