What is the resolution of direct view CRT HDTV? (1 Viewer)

[Peter Ping]

I am new to HDTV. I have a direct view CRT widescreen HDTV monitor (RCA D34W20). According to the specs sheet, my HDTV has 910 lines of horizontal resolution. I'd like to know how to translate this into HDTV format. Does this mean that it has 1618 vertical lines or horizontal dots (910x16/9=1618) or simply 910 lines or dots? How many lines of horizontal resolution for 910 vertical lines or horizontal dots? Also, how many scan lines or vertical dots are there according to the ATSC standard and how many for typical direct view CRT HDTVs? Thanks.

 

[Michael TLV]

Greetings

RCA spec is typically across the width of the screen.

910 x 1080 would give you the total pixel count.

Regards

 

[Jeremy Scott]

so hdtv's have more pixels then regular analog tvs?

 

[Jeff Gatie]

Jeremy,

Yes, that is what makes them HD - High Definition. Be carefull, though, they are not necessarily pixels. With CRT's, we refer to lines of resolution. Digital (LCD, DLP, etc.) displays are the only ones with pixels.

Standard television has 480 visible vertical lines, HD has 1080 (or 720) vertical lines.

MichaelTLV, Isn't it true that most direct views do not have the ability to completely display all 1080 vertical lines? I have noticed on all HD tubes (except for the new Sony XBR) that there are definite scanlines and/or a shadow mask visible at a distance that does not show scanlines/pixels on a comparable LDC/DLP/plasma. I have always heard this is due to the resolution limits of the CRT direct view tube. The 34XBR I saw was outstanding, but all others were lacking.

 

[Allan Jayne]

The problem with advertised resolution is that the description is often incomplete or not truthful. Correctly stated, lines of resolution must specify a distance. Textbooks almost always refer to video resolution, horizontal and vertical, using a distance equal to the screen height. Advertised resolution might use the electronic characteristics (bandwidth) of one of the internal circuits to arrive at the resolution figure, ignoring the fact that other circuits may be less capable or the picture tube may be unable to display dots that small or lines that thin.

So in the case of the TV advertised with 910 lines, you have to assume the worst case, that it can display at most 910 distinguishable dots all the way across the screen, if that.

In my opinion, the smallest dot for resolution evaluating purposes on a direct view screen spans any two of the three phosphor stripe colors. Using the dot pitch (distance between stripes or dots of the same color) and the screen width you can then figure the maximum "number of pixels" across. (For stripes, count all the reds, multiply by three and divide by two.) If this number is smaller than the advertised number, you have to go by this smaller number. The fatness of the scan lines limits the vertical resolution and also can limit the horizontal resolution over and above the dot pitch limitation.

Practically every CRT HDTV is indeed able to put a spot in any one of 1920 positions horizontally and any one of 1080 positions vertically which is what the 1920 x 1080 resolution of 1080i stands for. But due to various optical and electronic limitations, the smallest spot achievable might be larger than 1/1920'th the screen width. And source material might not have details that small.

Resolution as seen must take into account all deficiencies and losses. If you had a test pattern (I don't know where to find one for HDTV) what you see takes into account all deficiencies. If the smallest spot achievable was 1/1000'th the screen width, that TV set could be said to have resolution of 1000 lines per screen width and if it were 16:9, probably a vertical resolution of around 560 lines even though it is drawing all 1080 lines.

Video hints:
http://members.aol.com/ajaynejr/video.htm

 

[Michael TLV]

Greetings

A quick simple answer ...

The TV does not need to display 1080 vertical lines. It needs to display 540 lines progressive ... which is slightly more than the 480 that it is already required to do.

Recall that the 1080 is an interlaced figure ... showing 540 at any moment in time just like how 480i shows 262.5 lines at any time.

Scan line overlap softens the image and overscan hides additional image area.

Regards

 

[Allan Jayne]

True 540 progressive means that the even and odd scan fields coincide, that the TV is drawing scan lines in only 540 unique vertical positions rather than 1080. Although 1080i appears to have less resolution than 1080p, 1080i actually displayed as 540p will appear to have less resolution than as 1080i.

I do not regard a TV set as high definition if the vertical resolution is only in the 540 line vicinity, whether this is due to displaying 540p (having the defect known as line pairing) or due to having scan lines too fat.

 

[Michael TLV]

Greetings

Preaching to the converted here allan.

Just think of 1080i as 540P ... but that the even fields are for the next frame ... rather than the same frame.

Hence we reintroduce all that jitter that we see in 480i ... interlacing artifacts ...

Regards

 

[Jeremy Scott]

that probably explains why you can see the dots (lines) more on my brothers 36" Vega Analog tv then you can see on my 36" JVC HDTV

 

[Peter Ping]

I think there is some confusion here. Vertical resolution refers to the number of scan lines stacking vertically (in NTSC standard, the vertical resolution is about 480, but 720 or 1080 in ATSC HD standrad). Horizontal resolution refers to the number of vertical lines cross the TV screen). IMO, to measure the resolution per picture height, 680 x 480 for 4:3 ratio aspect is the format for 480 lines of resolution--both vertically and horizontally; 1280 x 720 for 16:9 is that for 720 lines of resolution--both vertically and horizontally. Am I right?

 

[Michael TLV]

Greetings

The proper way to report horizontal resolution is in TVL ... or TV Lines of resolution. This is based on a square ... width = height.

Few companies actually report their numbers like this and would rather use the larger width (edge to edge) number.

To an unsuspecting public ... when one set is quoted at 850 lines and the other is 1500 lines ... which obviously gets the attention. Of course, both sets are the same.

Regards

 

[RayL]

Michael TLV,I did not understand the reply you made to Peter Ping about the 1080 X 910 on his RCA.I would be surprised if that RCA has 3/4 of that 1080.

 

[Alex Antin]

In the past ...before HDTV... what the manufacturers were doing was using the video amp bandwidth and converting that to lines of resolution where 1 mz equals 80 lines of res. so a bandwidth of 10mz would equate to 800 lines.

Unfortunately it was a misleading number because none of the NTSC sets could reproduce 800 res. It might be happening again.

The only true way to check the res is as someone mentinoed...put up a test pattern.

 

[Michael TLV]

Greetings

This came from a while back ...

The RCA does 910 lines (left to right) by 1080 lines up/down.

Roughly 980,000 pixels worth of data.

There are also discussions out there talking about 1080 vertical lines actually being closer to 800 lines visible because of things like overlapping scan lines and such.

Considering that the source HD signals that we get in 1080i are resolution limited to about 1440x1080 anyway ... and how satellite and cable limit resolution to 1280x1080 .... getting 910x1080 isn't that bad.

Even a 410,000 pixels on an ED plasma for an HD signal looks much better than any non HD source.

(count the pixel array on the face of the RCA set. How many sets of RGB triplets can you count across the width of the screen. The number represents one of the bottlenecks. If you count 850 of these ... then the set can't show more than 850x1080 )

Regards

 

[ChrisWiggles]

I would not necessarily agree with that. Ideally, to correctly resolve 1080i, you'd need to have the spot-size to resolve 1080p. There are a lot of reasons why 1080i still looks great if you can't resolve 1080p, but if you have a display that can only resolve 540lines, I don't think I'd run 1080i on that. If you can resolve maybe 700-800 lines cleanly, I think 1080i will be better resolved there, and best at 1080p capable. Because if you're only able to resolve 540p and you're displaying 1080i, you're losing a TON of horizontal detail because your spot size is gigantic.

 

[RayL]

Michael TLV , if I count the pixels vertically, on my Panansonic CT-30WX15, would I not get around 700?
I do not see any form of overlapping, using a magnifying glass.
Or is this an incorrect way to check?