CurtPalme.com Home Theater Forum

**kal** · Posted: Sun Feb 05, 2017 2:11 pm Post subject:

Cool - Thanks for the link!

Kal

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

I do distinctly remember reading that an accepted industry standard for MTF evaluation for CRT is 15 percent measured MTF at 10 percent of rated max beam current. I seem to have not bookmarked that page so I haven't relocated it yet.

If I do, I'll post it.

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

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

I disagree with the statement that no CRT lenses are good enough for 1080p. We do it all the time and have very well resolved images and test patterns at that resolution. in fact they're good enough to show that our limitations on getting higher resolutions are NOT in the lens. Otherwise, you'd be saying that those who have posted well resolved images of resolution test patterns are lying, and I don't think that they'd appreciate that.

However, I'm not going to say that there aren't sharper lenses to be had. Just not likely for CRT.

I did a quick and simple test using an LED flashlight with a square LED chip in it, one with about 21 separate emitter connections,
which can be easily seen if you refocus the beam with a second lens.

Using this as a substitute for a CRT I was able to get a pretty cleanly resolved image of the LED chip face with an HD-10L lens.

Then I switched to a Minolta DLP lens made for the first generation 3 chip DLP machines (800x600 resolution or up to 1280x1024 at maximum) and did the same test.

There was absolutely no doubt that the DLP lens is much sharper. The difference wasn't even close.

But the DLP lens is too small in diameter (roughly 50mm/2.5 inches at the input aperture) to be usable with CRT.

So what's the problem? Why are our hideously expensive CRT lenses so relatively soft in focus?

It's because they have internal focusing mechanisms which complicate the optics and compromise image quality.

And it's because it becomes more difficult to optimize lens performance in a variable lens as it gets bigger. And by any standard,
your CRT HD-10 series lenses are enormous. They're the largest refractive optical lens assemblies I know of outside of some
ungodly expensive camera lenses used for special applications, and very rare and unusually large refractor telescopes.

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

You can disagree all you want, CRT lenses are NOT good enough for 1080p. I just letting you know the truth.

Okey let me say it like this. This is not hard to understand.
We need as high MTF as possible to resolve HD best, all type of technology need that. No one will go for the minimum requirements.

Info: Accepted industry standard for MTF 720P, 1080P, 4K evaluation for any type of lens are minimum 50% to accept the resolution. But am shore its something else for CRT lenses Smile

ElTopo · Joined: 07 Nov 2006 Posts: 1608

What you see is what you get and that is great with HFQ900.

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41