CurtPalme.com Home Theater Forum

[stefuel]

It's common practice to "de-focus" the blue for better color tracking. The question is, which direction. Do you under focus or over focus the beam for the desired results. I have actually measured the output of the blue in both directions and have found that 4 clicks of under focus results in almost exactly the same as 4 clicks of over focus. What I have not checked is if the same amount of de-focus (one way or the other) results in any sharper image.

I remember years ago, having many PM's with Guy Kuo about beam focus to the point that we were splitting hairs discussing beam focus as it relates to phosphor thickness. We finally settled on optimum focus being at the point where the phosphor is fused to the glass. However, no projector has the fine tuning to absolutly hit that spot given the distance travled per click. OK my head hurts. Food for thought.

[benareeno]

either way works as the there will be more blue with a bigger spot size...and don't worry about blue...it has no effect on sharpness with normal video! Sure..you may see some evidence with a windows desktop, but movies will look better with a lot of blue defocus!

[Chuchuf]

Benareeo is for the most part correct because you don't have to do that much defocus.
But, technically you want to defocus in the direction that makes the spot larger, not the direction that as you get larger produces a donut. You would also like the spot to stay round if you have your stig/CPC's adjusted correctly.

Terry

[garyfritz]

[Gary M.]

the trick to my much talked about sharp as a tack image is no blue defocus, if you go this route you will need to correct your greyscale problems a bit

I did this on a whim when setting up my 1352LC, I noticed that the blue tube in my unit was so sharp it was unreal and thought maybe I should try no blue defocus, did it and will never go back

the difference is easy to spot on movie credits

eat the blue bump and correct it with a scaler, it makes a totally difference image

my recently removed blue tube shows no extra wear at all from this, although I did use a 80" wide screen and ubber low contrast

-Gary

[benareeno]

I disagree with Gary here....if you sit around watching movie credits looking for sharpness issues...maybe heed his advice. If you like a rich and natural picture for movies/video...then do the blue defocus.

Or...judge for yourself if you see such a sharpness loss in your picture by doing it and making your own decision. All I ever saw was a far better picture...no loss of sharpness...or at least not noticeable at all.

[Mark_A_W]

You can't compensate for true tube saturation by fiddling with the gamma curve.

But that said, I also fiddle with my Gamma curves for each colour to get the best result.

[Gary M.]

[benareeno]

be sure to make your judgement while watching movies...not test patterns or movie credits. My 2 cents is up.

[Gary M.]

[kal]

[kal]

[kal]

[kal]

[Nashou66]

I agree with Kal and the others, I had an issue when i went to the colored HD 144's I could not get the green tint out till I defocus blue a lot and I mean a lot like in Kals description above. I tried it with the lumagen but I could not get it right, and when i defocused the Ftlb went up also.

Athanasios

[garyfritz]

Mine is defocused enough that it's noticeable (and often annoying, to me anyway) on sharp edges in actual video content, not just titles & crosshatch patterns. And I still have some blue hump -- see below.

Gary, the whole reason for defocusing blue is that the blue phosphor saturates long before the R/G phosphors. The saturation point isn't a hard cutoff, but a change in the slope of the in-vs.-out response curve. Once it saturates, increasing the beam current will still increase the brightness, but a LOT less. **IF** your scaler can boost the high end "enough" to compensate, then maybe that would work, and apparently it did for you. I assume you'd also have to boost the gain on the blue tube so you were able to drive it harder than the R/G, but that should happen naturally as a result of color calibration.

(For anyone who's wondering: defocusing spreads the electrons out over a larger area, so you get more photons out before hitting saturation. Which is also why people are talking about getting "more light" when they defocus. It's easy to tell when you've got the blue perfectly focused: that's when the blue output is the dimmest.)

Unfortunately a scaler is NOT in the budget for me, so I'll have to put up with blue fur.

[Nashou66]

Garyfritz you should start saving for a scaler like the Lumagen, lets put it this way if i was just starting and had to choose between the Moome card and the Lumagen to put money towards, the Lumagen would win hands down.

Athanasios

[Robert A. Hill]

Would adjusting blue astig/flare to give a (longish) vertical ellipse instead of a sharp dot also spread the light to increase brightness? This has been used to reduce the visibility of scanlines.

[garyfritz]

Yes Robert, anything that increases the dot size would have the same effect. Whether elliptical dots would be enough to do the job I don't know, but it would help.

[benareeno]

You're right Gary....absolutely right.

To spend 1k on a scaler in the 11th hour would be very foolish indeed!

Some digitals have adjustable gamma, 72 or 48 Hz refresh and ruler flat greyscales and accurate primaries to boot!

[Nashou66]

Not true gary go to the VP section on AVS forums and most have digitals PJ's amd or Panel displays and use Lumagen or Anchorbays VPxx line. Digitals need a VP more than CRT's do from what they are saying over there. Like the RS2 some say sucked before they added a VP to it.

Athanasios

[garyfritz]

Hm. Do they say what they used the scalers for? Color management?