Problem with image distortion on rear projection tv

wayne040576

Hi,

I've had a sony rear projection LCD tv (model KF50SX200U) for almost three years now. I noticed some distortion on the picture which I believe is Chromatic Aberration. Basically the red channel on the picture is shifted slightly to the left. It is more apparent when viewing text or dark objects on bright backgrounds. I had assumed that my lamp was on its way out so it didn't bother me at first and I didn't want to replace it until it blew because the damn things are so expensive. I've just replaced it today and noticed that the problem is still there. After some checking I've found that this chromatic aberration is related to lens problems. Although most people don't even notice it, considering the price I paid for the telly, I'd want the picture as clean as posible. I was wondering if anyone has any suggestions for reducing this or eliminating it (hopefully). Is it worth my while calling sony customer support or is this just something that happens with all rear projection sets? I read about some other makes of rear projection sets that are known to have this problem. Apparently this set uses a digital comb filter which is a technique that is commonly used to combat aberration.

Thanks

chopster

Is this not where the three colour guns are not properly aligned ? I have a pioneer rear projector that i have had for over ten years and in picture setup menu there is a utility to align all the colours together in the form of a ' + ' .
Maybe you have this utility somewhere in setup as well ?

wayne040576

chopster wrote:

Is this not where the three colour guns are not properly aligned ? I have a pioneer rear projector that i have had for over ten years and in picture setup menu there is a utility to align all the colours together in the form of a ' + ' .
Maybe you have this utility somewhere in setup as well ?

Yeah, that's what I thought. Unfortunately there doesn't seem to be an option for adjusting the colour guns in the menus. I was doing some more searching and so far what I've found with sony rear projection sets is that you have to open the set itself to find six knobs for adjusting the guns. Does anyone have a sony rear projection set and had to do this in the past?
It looks like I have to call the service centre.

ZENER

This effect is normally associated with older crt style projection units so doesn't apply in your case afaik. Chromatic aberration is an effect caused by poor lenses, most mobile phone cameras suffer this.

What happens if you turn the colour saturation down to give a b/w picture ? Do you get red fringes to the left then ? Does it happen with all sources including RGB SCART or just off air tv ? Red also focuses on a different plane to green and blue but you can't control that on LCD systems, there's no individual colour gun focusing.

Comb filters don't stop chromatic aberration they are used in PAL decoders to help improve display quality and reduce PAL artifacts.

ZEN

wayne040576

ZENER wrote:

This effect is normally associated with older crt style projection units so doesn't apply in your case afaik. Chromatic aberration is an effect caused by poor lenses, most mobile phone cameras suffer this.

What happens if you turn the colour saturation down to give a b/w picture ? Do you get red fringes to the left then ? Does it happen with all sources including RGB SCART or just off air tv ? Red also focuses on a different plane to green and blue but you can't control that on LCD systems, there's no individual colour gun focusing.

Comb filters don't stop chromatic aberration they are used in PAL decoders to help improve display quality and reduce PAL artifacts.

ZEN

When I turn the colour down to a b/w picture it still happens.
It happens with all sources, aerial, RGB scart (dvd player, sky box etc). I was playing with these to adjust the picture that each outputs (RGB or PAL) but nothing helped.
Even the text on the system menus have the problem.

ZENER

I don't have much experience with LCD RP units but I presume that unlike CRT units it has just one lens. When you were replacing the lamp you didn't happen to notice much dust buildup on the lens did you ?

Did this happen suddenly by the way, or was it it a gradual thing ?

ZEN

wayne040576

ZENER wrote:

I don't have much experience with LCD RP units but I presume that unlike CRT units it has just one lens. When you were replacing the lamp you didn't happen to notice much dust buildup on the lens did you ?

Did this happen suddenly by the way, or was it it a gradual thing ?

ZEN

I didn't see the lens itself but there was some dust in the lamp cage and surrounding area. I didn't do much cleaning around the area.
I first noticed this almost a year ago. I'm not sure whether it showed up suddenly or just built up to a stage were I could see it. At first I had assumed that the lamp was on its way out so I bought a new one and just left the old one in there until it blew. It only blew yesterday morning. Up to then the problem was annoying but I was prepared to live with it until I replaced the lamp. It doesn't seem to have gotten any worse over time.

ZENER

I don't see how the red could have been specifically effected when the display element is a LCD unit rather than 3 seperate CRTs.

I've downloaded the user manual so I'll scan that and see if it comes up with aout.

Try cleaning the lens for starters just in case.

Is the displaced red signal as sharp as the blue and green signals by the way ? For example does a thin white vertical line appear blue/green rather than pure white ?

ZEN

wayne040576

ZENER wrote:

I don't see how the red could have been specifically effected when the display element is a LCD unit rather than 3 seperate CRTs.

I've downloaded the user manual so I'll scan that and see if it comes up with aout.

Try cleaning the lens for starters just in case.

Is the displaced red signal as sharp as the blue and green signals by the way ? For example does a thin white vertical line appear blue/green rather than pure white ?

ZEN

As far as I can tell, a vertical white line is still appearing white, it just has a red 'shadow' offset to the left.
I'll try cleaning the lens. I probably won't get a chance to do that until friday or saturday.
Thanks

wayne040576

Well I made an attempt at cleaning the lens. It is enclosed in a cube behind the lamp. Each of the vertical sides seem to have either a lens or multipaneled mirror. I wasn't going to risk removing it so I couldn't see it properly. This means I was only able to clean the glass on the lamp side of the box. Didn't make any difference to the picture. I cleaned up the surrouding area. I noticed that the floor of the box had a bit of dust in it too but I was unable to get at it.
Think I'll have to get it serviced.