CurtPalme.com Home Theater Forum

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

I am setting up my BG1209s/E again and have run into something I cannot get my head around.

I have played around with scheimpflug (since I wasnt able to get good focus top center and bottom center with the same optical center focus setting). I am now able to get very nice focus center top and bottom BUT I dont feel that I get the corners as good as I think I should be able to. I think that my scheimpflug is pretty good for diagonal focus, but I have to choose from getting either left top and bottom corner OR right top and bottom corner focused when using optical corner focus.
To me, it sounds like it would be good to be able to adjust the tubeface vs lens not only diagonally (as in scheimpflug) but also left right.
I am only playing around with green (red and blue is actually pretty good).

Hope I make sense!

Any ideas?

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

It's a lot easier to see how scheimpflug affects focus when you optically defocus the image so that the grid lines are all very blurry.

Now look at the WIDTH of the grid lines across the screen (horizontal lines) and top to bottom for the vertical lines.

As you adjust scheimpflug, you will see the width of the lines change. You want the lines to all be as even in width as possible,
and THEN you can refocus the lens.

This makes it a LOT easier.

Hulio · Joined: 15 Apr 2006 Posts: 469 Location: Belgium

To me, it seems like you are overlooking something. The purpose of scheimpflug adjustment in not to get the best focus (you do that with the focus yoke, static astig, dynamic astig, electronic and optical focus).
When adjusting scheimpflug, don't look at how good or bad your focus is but take care that your focus plane is balanced diagonally. With another words, the left top corner has to be at the same sharpness (or blurriness) as the right bottom corner.
The same for left bottom-right top. You are just moving the CRT faceplate with regards to the screen, compensating for the off-axis projection. If the projector is at the right distance, square to the screen and at standard 10,5 throw-degrees, it is quite impossible to have a diagonally good focus plane, but not left-right.
Also, be aware that after you are setting the best optical and electronic focus, dynamic astig etc, you'll have to re-check scheimpflug. It's a iterative process, one adjustment influencing the other. You'll get than to one point, where you can't get it beter. The slightest touch of the scheimpflug and, bam..a huge difference on the screen.

nombz · Joined: 09 Mar 2006 Posts: 119 Location: Stockholm, Sweden

Thanks for the advice. After having a bit more patience I was able to get very good focus all over the screen for green. I have never been able to see the phosphor grain as clearly in every single corner as I do now.
Now lets look at the other tubes.... Smile

Thanks!