CurtPalme.com Home Theater Forum

ElTopo · Joined: 07 Nov 2006 Posts: 1640

You could do 2048 x 1600 on each.

This would give you 3840 x 1600 (scope in 2.4) with a blend zone of 256

cheers

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

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

1080p is most certainly highly resolvable on the best CRT projectors. Maybe not with an MTF of 100 percent, but the industry standard for defining resolution capacity is 15 percent measured MTF at 10 percent of peak current drive levels. All the top gun 9" machines can be expected to meet that standard in stock condition, and actually they do it rather easily. The part about doing the test at 10 percent of peak drive levels is routinely violated and MTF is often quoted at a much higher drive level.

Going back to about 2004 I was able to achieve clearly defined one on, one off test patterns on the green tube of a Marquee 8000 at a test resolution of 2048x2048, 60 Hz refresh rate, coming out of a Sencore CM2125 monitor analyzer. This was clearly visible and razor sharp on the CRT face but due to the optical limitations of the HD-8B lenses it could not be cleanly resolved on the screen. This was done using an alternative focus yoke, the very first "frankenyoke" I ever tried, which lacked astig windings but then again, the 8000 didn't have astig anyway. The projector was otherwise bone stock although the green tube was an alternative type, not a 180DMB. I think it was a P16LNN type?

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

Again If you manage to show a picture, does not mean it will manage the resolution, even you know that CM J, no point of this discussion in 2017 its dead.
But yes 1080P SDR look good on top 9" CRT with correct color c-elements so it track Rec709 D65 fine.
Maybe not with an MTF of 100 percent. Correct, more like 20-40% if you are happy with that today then ok. Limitations stays in the lens like you say. They were made for a totally different purpose back then.

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

The majority of lenses found on the remaining 9" CRT projectors still in home theater service are capable of resolving not less than 12 line pairs per millimeter. If you do the math, you will find that this is quite sufficient even for resolutions approaching 4K.

A 9" CRT is capable of supporting a 16x9 aspect ratio raster with a width of 6 inches and a height of 4.5 inches.

4.5 inches is 114.3 millimeters. That's 1371.6 line PAIRS (2743.2 lines) that can be written on the 4.5" tall raster before you reach the limit of lens resolution as defined by the lens manufacturer's testing.

We only have to resolve 1080 lines vertically but the lens is good for 2743.2 lines vertically in the same area.

So, no problem. The lens is NOT a limitation on achieving full 1080p HD. The lens isn't even CLOSE to being a limitation.

Incidentally, our CRTs are not built for rec. 709 colorimetry and do NOT achieve it.

Our CRTs are built to achieve NTSC (Rec. 601) colorimetry but only achieve it with filtered C elements on red and green.

No, you're not seeing the full rec. 709 color gamut on your CRT projector.

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

hal · Joined: 28 Nov 2012 Posts: 100

http://www.matrox.com/graphics/en/products/graphics_cards/m_series/powerdesk/edge_overlap/

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

You can easily Google search and find CIE chromaticity charts showing the various standards with their color gamuts mapped to the chart. While Rec. 709 is not very far from 601, comparatively speaking, the jump from 709 to UHD's rec. 2020 is dramatic,
and it encompasses all other standard gamuts within its borders.

kabuby77 · Joined: 28 Mar 2011 Posts: 147 Location: Italy

Measured my 1292 with i1D3, the 3 primary are perfectly on reference

CIR Engineering · Posted: Sun Jan 29, 2017 10:21 pm Post subject:

jbmeyer13 · Joined: 03 Dec 2010 Posts: 1135

**kal** · Posted: Sun Jan 29, 2017 10:52 pm Post subject:

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

About REC709 on CRT just as I said before, no problem as many have now pointed out, you need color filtering to reach it. I got almost the same experience like you - CIR Engineering. And the calibrating went good on 30IRE and 80Ire with the greyscale but hard to get a low DE in total average, with good linear gamma at 2.4.
Customer happy.
Also about the lenses, that can easily be read wrong and misunderstood . In the time when CRT came the resolution 1280x1024 were almost a fantasy resolution. And most lenses according to specification and "also from CRT techniques" were maxed at this 1280x1024 (if you factor in high MTF) so far from 1080P. Also if you read about the MTF on best CRT lenses, 1080P might be under 15-20%MTF. To get around 80-85% MTF the resolution were 480P and about 50% in 720P. So what jbmeyer13 says are correct. So one of the limitations for CRT are lenses. So, 2741 lines, I will say is fantasy and not reality.

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

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

Just to be clear about it, the industry standard for evaluating MTF is to perform the evaluation at 10 percent of rated maximum beam current (or equivalent brightness) and when the brightness variance between the scan lines and the gaps is 15 percent, that is the actual point at which MTF is specified for CRTs.

15 percent MTF at 10 percent of max drive current. The highest resolution that meets this standard is officially the highest resolvable resolution for a CRT. It may display higher resolutions than that. But not RESOLVE them to standard.

10 percent drive is not where we usually do our viewing. But that IS where MTF performance is evaluated.

Anybody who's ever played with the contrast control knows that resolution and contrast levels are interrelated. Turn it up high enough, and you will start to lose detail.

If you really want to know the ultimate resolving power limitations of your lenses, I can think of a way to do this. What you would do is have a miniature resolution chart made in the form of a printed clear decal, printed at very high resolution, and apply it directly to the CRT face and focus on it with the CRT backlighting it. Two catches to this method, though: 1: It will have to be in the coolant since most CRTs are liquid cooled. 2: The lens system is set up to focus on the phosphor layer, not a half inch short of it at the front of the CRT glass. So a modified lens may be required.

If I really wanted to do this I'd modify the faceplate of a broken CRT, cleaning it thoroughly of all traces of phosphor, polishing the inside surface flat and smooth, applying the decal, and backlighting it thru the lens. The advantage is I could do this without actually even having a projector. The disadvantage is the hazards of working with broken glass and chemicals that are normally contained within the CRT. (I do not recommend snorting the phosphor under any circumstances. It will not get you high. But perhaps you could call it "glow" rather than "blow". )

**kal** · Posted: Sat Feb 04, 2017 11:08 pm Post subject:

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

FYI:
http://www.curtpalme.com/forum/viewtopic.php?p=100751#100751

Mr Jaeger · Joined: 24 Mar 2015 Posts: 41

gjaky · Joined: 05 Jun 2010 Posts: 2802 Location: Budapest, Hungary

It is indeed interesting reading.
What is strange though that they often found the horizontal MTF better than the Vertical, because if the aspect ratio is set well then ideally they should be equal, but in the horizontal plane the bandwidth of the video chain also affects the MTF so, as I see the horizontal MTF never can exceed the vertical MTF (that is only limited by the focus system (optical or electrical)).

Also let me share a personal experience, with my XG135 I use 1080i 96Hz and it is not very well resolved, although using 1600x900P I can see pixelation artifacts of the movie material, while the MTF supposedly still not very good, so at the end of the day I find 1080i still better.