CurtPalme.com Home Theater Forum

[gjaky]

[mp20748]

gjaky wrote:

Let's do a simple experiment: let's stand in front of your TV, let's say it a 42" 1080p model, If you watch it from 2 feet, can you see the pixels, that mean at that "setup" the resolution is too low. watching the same scren from 10 feet you won't see much pixels, meaning that the resolution is better than what you can see. From 1 mile you can't even see the TV...

You're really saying the same thing I mentioned because nothing you mention here has anything to do with "Viewing Angle"

My understanding of Viewing Angle from the Industry is the position of the projector to the display device or screen, or the seating position of the person and/or people looking at the viewing device or screen for optimum image presentation

The key word is: ANGLE

[cmjohnson]

If you only have an 8" machine for tests, that doesn't invalidate your MTF results in any way, shape, or form. You just have to note the raster size you are working with, which can be mathematically scaled to correlate with the results from a 9" machine.


I have a relic of the AmPro light valve days which is kind of interesting. It's a 3" diagonal CRT equipped with a near-IR phosphor, which shows as dim red to the eye. Most of its output is not visible to the eye but you can see some output. Except for that LC light valve bonded to the CRT face using water clear epoxy.

It came from one of those AmPro light valve 7000 series projectors.

The rated resolution capacity of that 3" CRT assembly is not less than 2500x2000 at 50% MTF.

The point is that MTF is a useful rating on ANY crt of ANY size. Just make note of the size along with the measurements.

Believe me, I WILL accept objective, not subjective, measurements.


Now as for whether or not 4K is going to make a meaningful difference, all I can say about that is that when I first saw full
1080p running on my Marquee, I thought it was like looking out a window.

Then, when I started to see new technology TVs running 4K demo material, I thought I was looking out a window but there was no glass in the window frame. This, on a screen not HALF the size of the one my Marquee uses.

I have absolutely no doubt that visually significant improvements will result as we are able to achieve higher displayed resolutions.
But, we must realize that 4K is almost certainly the ultimate limit for even the best, most highly modified and tuned CRT projectors.
However, any improvement over 1080p will be welcomed. 2K? That's not difficult. You won't even need to mod most machines for that. We might even be able to get to 3K without spending a whole lot of money. I hold 4K as an ultimate goal that MIGHT be achievable if we can find a way to tickle RGBHV signals out of an HDMI 2.0 data stream.

[redfox001]

Angle between two lines going to the edges of the screen. If you are further away the viewing angle is smaller. Glad I could assist

[MeV]

[cmjohnson]

Going back to straight and simple numbers, if your screen is 8 feet wide like mine is, at 1080p resolution your resolution is 20 pixels per inch. (20x96 inches = 1920) At 4K, 3840 pixels across, then your resolution is now 40 pixels per inch.

Would you really be able to see the difference? Based on my own observations, at my seating distance, I say yes. Your results may vary. Not everybody's eyes are the same.

But I don't think that you'd see an improvement at 80 pixels per inch at 8K resolution. Not at the same viewing distance.

Currently, my projector is in need of a light overhaul. While the tubes are still minty fresh with under 500 hours on them, the glycol is contaminated with fungus or corrosion and the blue is beginning to see a bit of murkiness. I'll be taking the CRTs out soon and refreshing them and resealing the aluminum surfaces and while I'm at it, replace the tank hardware with stainless. Possibly new bellows, too, depending on their condition after unsealing them.

Due to the need for all this work, my PJ is not performing to standard. After the overhaul, it should.

If I choose to install the super tubes in it, then that'll really provide some interesting experiments.

[ecrabb]

[mp20748]

[cmjohnson]

Well, that also depends very much on what kind of display you're talking about.

With an LCD flat panel display, viewing angle refers to how far off the central axis (right in front of it) you can be and still see a good quality image. You will probably recall that with early generation LCD displays, you had to sit right in front of them to get a good picture. Go much off axis and you would get color shift and then a dropoff in brightness that got progressively worse as you got farther off axis. This phenomenon is unique to flat panel direct view displays and is not a problem for any current generation LCD displays as used in computers and televisions.

For any other display type that does not suffer from viewing angle restrictions, viewing angle often refers to the angle presented to the viewer by the edges of the screen relative to his eye. Closer to the screen, wider angle. Farther from the screen, narrower angle.

I think we all understand this. So why quibble about a matter of semantics?

[mp20748]

[cmjohnson]

Oh yes, I do recall the challenges posed even by your typical RPTV, now that I think about it. You'd get color shift as you changed your lateral position relative to the screen, reddish on one side, bluish on the other, but in later generations they improved the performance of the fresnel and lenticular screen elements as well as the internal optics to yield a more uniform, rather than lambertian, distribution property.

I remember spending some time playing around with various translucent papers and mylar films and an RPTV with the screen taken out of it, to gain a better insight into projection optics by visualizing the light path with the aid of the paper. I found that certain oiled papers made a nearly ideal screen, yielding excellent non-lambertian power distribution, sharpest focus, and no lenticular or fresnel artifacting, but it was not a practical screen for regular viewing. For one, it had zero gain. Plus, it was oiled paper. Not exactly a durable screen material.

[Spanky Ham]

[cmjohnson]

A CR of 80 to 1 is perfectly fine for data presentation. Who here has a CRT projector installed in his home theater for data projection? Show of hands? Shout out?





Yep, as I suspected. No hands, crickets only.

Sony sold some projectors expressly for the HT market, and they would understand CR and black levels as we want them to be.
Same for the guys at Barco involved with the Cine line.

But outside of them, only specialist A/V companies made any effort to maximize CR with custom modified and/or custom set up projectors from the usual offenders....I mean, manufacturers.

Of course we know this.

[mp20748]

SDI 4K (Pro - SDI) mini converters plus demo


https://www.aja.com/en/products/mini-converters/4k2hd


https://vimeo.com/119519462


----------------------------------------------

A good read on the benefits of 4K conversions to HD (1080P)



http://pro-av.panasonic.net/en/dvx4k/pdf/ag-dvx200_tech_brief_vol1_en.pdf



Sharper HD Footage
: When you have a much larger source image to work from, shrinking
it down to HD size can make for the sharpest, clearest HD images possible. A super-sampled
ultra-high-definition image, when resized down to HD frame sizes, can result in images that
hold as much detail as the HD frame size is capable of retaining. This means that it is possible to
get sharper HD images from a 4K/UHD camera, by resizing the images in post, than you would
get from even a very high-performance HD camera.

Reduced Noise
: Another benefit to downconverting 4K/UHD footage to HD in post production
is that you’ll see a significant reduction in visible noise in the image. When converting UHD/4K
footage down into 1080p footage, each 2x2 group of UHD pixels are used to create a single pixel
in HD. Combining the 2x2 group of UHD pixels can result in “averaging” the noise from each
pixel together, resulting in smoothing out the noise and greatly reducing its visibility.

Increased Color Resolution And Bit Depth
: One excellent benefit of downconverting UHD/4K
footage to 1080 HD in post is that you can realize an increase in proportional color resolution
and a notable increase in bit depth. The AG-DVX200 records 4K or UHD footage at 8 bits per
pixel and utilizes 4:2:0 color sampling. After downconversion, the resulting footage has 10 bits
per pixel and 4:4:4 color sampling! Yes, you can convert 3840x2160 8-bit 4:2:0 recorded footage
into 1920x1080 10-bit 4:4:4 footage in post



.

[redfox001]

It might be just like audio. A huge improvement came from recording at 192kHz but no improvement came from playing at 192kHz. On the recording part filtering became much easier and no details where lost or artefacts introduced in the below 20 kHz audio by recording and post processing with the higher sample rates.

I think uhd playback will be gone in a few years. People will probable hold on on their blu ray players with the better blu rays on the market.

[cmjohnson]

As long as people think that Bose makes really good sound equipment, they'll NEVER hear the difference.

Audio equipment that has the resolution to deliver sound superior to the CD standard is expensive, particularly the speakers.

However, even then, you're most likely to notice the subtle details only if you are inclined to look for them. It's people like me, and presumably others participating in this forum, that care more than the average person about picture quality, and, presumably, sound quality as well.

[redfox001]

Well you disagree with Mike Parker how to explain that?

[Spanky Ham]

[cmjohnson]

Sure, but I was talking about back in the day when the CRT projector was what they sold, digital was not yet big and well developed, and they didn't sell many projectors into the home theater market, mostly because that was at the time very much a small niche market. Today, most companies making projectors that wants to keep their doors open is selling mostly home theater product and some of them don't even have a product line tailored for industrial and commercial applications.

Interestingly, VDC is totally focused on government contract work, with some commercial sales, does NOT cater to the home theatre market, and in their case that business model is successful.

Actually, Barco also has a similarly successful business model, and that's why I'm not saying that you HAVE to cater to home theatre in order to be successful making projectors. But we know that most projectors sold these days are aimed at that market.

[redfox001]