CurtPalme.com Home Theater Forum

[stridsvognen]

Ecrabb..

I know you will keep on, untill your sure no one will post any home grown ansi measurement, like its blasphemy to your religion.

Your a skilled writer, im not..

If we emagine we are in Germany.. The year is 1933, and my name is Adolf, ill for sure ask you to be my minister of propaganda.

[stridsvognen]

[CasetheCorvetteman]

[Spanky Ham]

Strid,
Boil it down. Do you want us to help you refine your measurement taking ability? Do you want other peoples measurements? Exactly what are you wanting to accomplish. The latter question is not really going to tell you much, because of so many variables. As has been stated the most important is the room. The former question has been answered. As Crabb has said, we defer to others with more knowledge and desire to do this. I linked you to an article by Darin. There are plenty of threads on AVS discussing this. I personally don't need to do this first hand, as plenty of other people have already done this and measured the results.


Now, do I think you taking measurements is productive? Yes for your situation. Based on your numbers, I would say your room is really holding you back. IIRC, Guy Kuo found through his experiments that blacking out the first meter (I used the metric system ) into the room from the screen was the most important followed by the back wall. There is a thread discussing this on AVS somewhere. You could try a shadow box around the screen, but IIRC Kal tried it and didn't like it.

As for absolute numbers to shoot for, IIRC an AC CRT tops out at around 100, a LC CRT at around 175, LCOS at around 300, DLP at anywhere between 500 and 1000. I think the variance in DLP is from the extreme difference in quality of lenses used from cheap $1k pjs to expensive $50k pjs. I don't keep up that much anymore, but IIRC the JVCs were a little down from the 300 number. The best way to know differences in pjs is to find people who have tested multiple pjs in the same (hopefully black cave) environment usually a reviewer like Greg Rogers or Kris Deering. Darin used to, but I think he has cut back. I do know Darin does his testing in a black hole, because Curt described it once. I remember the post, because Curt said he thought the sound was really good and was shocked (amused) to find the speakers were inexpensive Sonys.

I might add that only a select few go to the extreme. I remember Kris (I think Crabb was at the next table) saying at some point he just wants to watch the movie.

[stridsvognen]

Jesus.. You Guys just dont give up do you.?

What about spending some energy measure your ansi contrast in your rooms.. and post the nr.. tell how you measured and describe your rooms.

I did read the projector bible more than one time, so no need quoting it here.. Im looking for a potential new religion..

Dont block free thinking with your narrow minds, and lack of curiosity.!!

[ecrabb]

[stridsvognen]

[ecrabb]

[ecrabb]

BTW, I think your project to mask the lenses was a very good idea. I was always going to do it to my G70, but never got around to it. I have no doubt there was a reason that NEC did it on the XG LC machines, and that the reason was to increase ANSI contrast. Maybe it wasn't much, but considering it probably cost almost nothing to add it to every machine, it's a great improvement.

I didn't see in the thread... Were you able to measure in improvement in before/after? With the ANSI readings you got, I'd guess that either your methods, your room, or both together were making it impossible to measure whatever real benefit to ANSI that mod gave you.

SC

[Spanky Ham]

Wow, maybe I could have phrased it better but I thought I was trying to both educate and be helpful. I guess not, so I am out.

[CasetheCorvetteman]

[CasetheCorvetteman]

[HogPilot]

[greg9518lc]

Bump for the Wolfman

[thewolfman]

Thanks, interesting read. I always thought the idea of masking the tube face was never followed thru.

Btw, bring Kurt back in, he has been punished long enough. I have nothing against him, we all need second chances in life so lift the ban on him.

[cmjohnson]

Attempting to mask the C element would be counterproductive. The C element exists INSIDE the focal planes of the optical system and any alterations to it by adding obstructions will REDUCE contrast levels. The masking would not be directly visible as masking as it would be in a non-imaging section of the optical path.

The optics have two imaging planes: The CRT face and the screen. Any obstructions added between those two planes will be
non-imaging and reduce contrast. Basic optical theory.

In any event, the single greatest contrast improvement that remains to be addressed probably will NOT be, due to huge costs involved. And that would be to address the lateral scattering of light in the phosphor and aluminization layer itself, right there in the CRT. This can be addressed by giving the CRT a faceplate made of fiber optic glass, and in fact this HAS been done for some
specialty applications, one of which was the 3" high res CRTs behind every light valve in every AmPro light valve projector. These
small 3" CRTs were rated to resolve 2500x2000 and if you compare resolutions and phosphor areas between those tubes and
our 9" tubes you can understand what an incredible level of performance that is out of such a small tube.

The problem is that you could not afford 9" or even 8" tubes made with fiber optic faceplates. It would probably push the cost
per tube to something around 10,000 dollars each. The reason is that making fiber optic faceplates is a very labor intensive process indeed. Millions of individual fibers have to be laid up in a stick, and NOT tangled, and then fused together, slices sawn
off, polished, and not broken or damaged in the process.

If you were well heeled enough to want to try it, contact Lexel Imaging and ask them to custom engineer it for you. They would
probably have to do it with Sony 09MEX bell glass as the Sony design uses a flat glass faceplate anyway.

I have seen one of those 3" AmPro light valve tubes in operation with no light valve attached. It's a very interesting visual characteristic, as there appears to be no glass in front of you. It's like you removed the glass and there is nothing between
the generated image but the space between it and your eyes. It doesn't appear to be behind glass at all. And there is very,
very little light scattering on the tube face even at high contrast levels. There is virtually no halation, and what little there is
occurs within ONLY the phosphor layer and not at all within the faceplate glass.

[greg9518lc]

3

[cmjohnson]

HOW exactly can an amplifier connected to the cathode and G1 grid affect beam spot size?

Please explain by any means available to you. Be aware, any claims may be subject to detailed analysis and investigation by
more than one highly qualified electrical engineer with extensive experience in video amplifier circuit design as it pertains to
driving the electron gun assembly in a high resolution cathode ray tube.

I would LOVE to find out that there is in fact a means by which a modified or improved neck amplifier card can reduce beam
spot size, but there is no mechanism by which that particular concept can be realized that I am aware of.

I have great respect for MP but I do not believe that this particular claim will hold up to actual analysis by measurement.

As a matter of fact, I recently bought THIRTEEN absolutely brand new, still sealed in the wrapper, VDC neck cards, the "compatible" type, and I can tell you, I did NOT see that the ones I tried were any sharper. Spot size did not change as far as I could tell. Since I'd already read of MP's claim that they were sharper, I went looking for evidence to corroborate that claim
and was not able to come to the same conclusion based on what I saw for myself.

The neck card's primary function is to control beam current. It has secondary functions for providing heater voltage, providing bias, and controlling grids. But none of these are functions affect electron beam spot size except for the inevitable increase in beam spot size with increasing beam current. This is because the electron beam profile is fundamentally Gaussian in
nature. Interestingly, its interaction with focusing systems can make it more approximate a square wave profile, but right
off the electron gun assembly, it's always a Gaussian profile with a small amount of additional diffraction effects that aren't generally noticeable.

But there is no means by which a neck amplifier can make the beam smaller in diameter. There simply is no mechanism to do that.

[cmjohnson]

As long as the subject is open, how about taking a look at the electronic crosstalk between the RGB channels in the Marquee chassis? If the contrast is up and you look in the red or blue tube faces directly, you can see shadows of the menus that are active on green. So there is a definite and detectable level of crosstalk in there, which MUST have some slight effect on the image, even if it isn't generally noticed on the screen.

[racerxnet]

Here are some pictures of the mask I made to solve the light scatter from the tubes and lenses. I have a 1/8th inch thick piece of foam that gets adhered to the outer mask and contacts the tube housing for a complete seal of the lens assembly. Its flexible enough to move with the adjusting allen screws.

MAK