Misconvergence/Chromatic aberration: post screenshots here

**Blaser** · **03-31-08, 07:52 PM**

We know that misconvergence is common to 3LCD projectors because they have 3 panels that have to converge at a single point. Failure to do so results in misconvergence.
Misconvergence will vary from projector to another but won't vary given a single projector either it is used in telephoto or wide angle.

Chromatic Aberration on the other hand may vary to some degree, and might be best in a telephoto setup.

Chromatic aberration has a different origin than misconvergence as it does not happen in the panels, but in the lens. I'll try to make it as simple as possible by saying it is distortion in colours produced by the lens. It is the lens that causes different colors not to focus at a single point. Basically Chromatic aberration is caused by a lens having a different refractive index for different wavelengths of light.

There are two types of chromatic aberration:

1) Longitudinal chromatic aberration (tracking error):Difference colors (wavelengths) will focus on different image planes. Projectors use zoom lenses and therefore this form of aberration will affect the picture to certain extent. The amount varies as the lens is zoomed. This form is easier corrected in lenses whereas the following is more difficult

2) Lateral chromatic aberration (registration error):
This is due to the lens magnifying different wavelengths differently.

Chromatic aberration makes "fringes" of colors around the image (see image below obtained from Wikipedia).

**Blaser** · **04-18-08, 06:53 PM**

Epson pro UB (TW2000) has been criticised quite a lotfor QC issues and specially misconvergence. Depending on screen location, my unit has from perfect to 1.5 pixel red misconvergence (Red is worst, as most visible). It also has some green misconvergence from perfect to 1 pixel.

What comes in mind is it is not very easy to perfectly adjust LCD panels to obtain no deviation, and I also beleive this problem is associated with any 3 LCD projector but probably with difference tolerances.

If I look for it I can definitely see its effect from watching position on credits and high contrast scenes, but it is not distractive unless I concentrate hard on it.

What about misconvergence with your projectors, pls describe!

Thanks!

**Blaser** · **04-23-08, 06:24 PM**

Here are screen center, worst:raped: and best

... Pls post yours and discuss!

**Blaser** · **04-30-08, 08:25 PM**

Does this mean nobody's having misconvergence issues?? Well that's good news but hard to believe!

**Prof.** · **05-01-08, 08:30 PM**

Can't post here..I have a DLP..

**Blaser** · **05-02-08, 04:42 AM**

Great! A DLP will not have such misconvergence problems, but it might be prone to some chromatic aberration.
I would like to see a panasonic 2000 and other LCDs screenshot.

**Blaser** · **05-10-08, 02:36 AM**

Quote:

blaser wrote:

Great! A DLP will not have such misconvergence problems, but it might be prone to some chromatic aberration.
I would like to see a panasonic 2000 and other LCDs screenshot.

Is your misconvergence so bad on your projectors so you don't even want to post a screenshot?

**Timoxx4** · **06-08-08, 09:03 AM**

I have a Panasonic AE900 with a misconvergence problem. But theres naught i can do about it

**Blaser** · **06-08-08, 01:14 PM**

Welcome Timo

A degree of misconvergence will most of the time exist in LCD projectors. How bad is it on your projector? Do you see it from watching distance? Post a screenshot.

**Blaser** · **06-08-08, 07:49 PM**

I have noticed misconvergence is almost imperceptible on high resolution material. I have just watched Ice Age 2 on BD but couldn't find any sign of misconvergence at all

.

This phenomenon is accentuated once the resolution and transfer are not top notch such as poorly mastered DVDs or SD TV.

**Timoxx4** · **06-09-08, 09:57 AM**

Yes i can get a screen shot of it for you if you like.

I don't notice it watching movies really. Although they might appear sharper or more detailed if the convergence was correct ?

I see it on text. Its most obvious when i bring up the projectors main menu and all the text has green down one side and red down the other.

I will snap a pic of it tomorrow to show you.

**Blaser** · **06-09-08, 12:42 PM**

If you're up to 1 pixel, it's pretty normal foran LCD. It is unfeasible to perfectly align such panels. We wouldn't be able to own such a perfect projector.
Sometimes, these panels also take a hit during shipping, so it might not be fully controllable. But if it does not bother on program material, that's it ... just enjoy

**tonyvdb** · **06-09-08, 03:36 PM**

My Sanyo was out by just a slight bit but was able to correct it in the service menu and it made a huge difference.

**Blaser** · **06-09-08, 03:47 PM**

You're really lucky to be able to access the service menu and even more to be able to control misconvergence in a way

How bad was it and how good is it now?

**tonyvdb** · **06-09-08, 03:58 PM**

Very much like your first picture the red and blue were off in both directions but now its almost bang on. I was able to adjust vertical and horizontal on both the red and blue panels, I left the green alone.
even though its 720p HD looks great.

**Blaser** · **06-09-08, 04:06 PM**

Thanks a lot. The only difference is my FP resolution is 1080p which makes 1 pixel quite smaller than a 720 P FP.

**Timoxx4** · **06-10-08, 04:16 AM**

Ok i took some pics of my panasonic AE900 main menu screen showing the misconvergance it has.

This is from my seat about 4 meters back from a 92" screen.

This is an extreme close up about 20 inches away from screen.

And here a pause simble from an Oppo DV-983H also from 20 inches away.

It looks pretty bad close up like this but from my seat it is not so noticable if at all. It would be great if they made it so you could adjust the convergance in the setup menu like a rear projector TV set.

This is the first projector i have ever had so hopfully next one will be better when it comes time to upgrade. A 3 chip DLP would be good but i could never afford one.

**Blaser** · **06-10-08, 05:35 AM**

Yeah! I am not sure but this looks like something around 1 pixel off. That should be acceptable or not depending if you see it from watching postion or not. Of course you don't have to make excessive efforts, but only if it bothers or not during normal material watching.

I have yet to see a single LCD projector that doesn't have any misconvergence issue everywhere on the screen....That is a "technology limitation".

Nevertheless, that doesn't mean PQ will necessary suffer or so. As far as a 3 chip DLP is concerned, don't be discouraged.... While it might be truly expensive now, we don't know what will happen in 2 years for ex. not to mention each technology has its limitations

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