Resolution Screen Size Relativity (1 Viewer)

[Neil McCaulley]

Hello all,

This is something that has been bugging me for some time. Maybe someone out there can explain it to me.

I have a 46" Widescreen Hitachi HDTV. It's screen resolution is 1080 vertical lines of resolution and 720 horizontal lines. But I also noticed that a 55" TV has the exact same amount of resolution. How can this be? If the screen size gets bigger, does this not mean that there should be a relative increase in the amount of vertical lines of resolution? The only thing I can think of that makes sense is that the physical width of the resolution lines are wider in a bigger set, than in a smaller set. Again, would this not mean that the picture quality gets degraded the larger you get because the lines of resolution are not as fine as a smaller set?

Someone out there please explain this to me.

 

[Jack Briggs]

Neil, the original broadcast is at 1080 lines of interlaced resolution. A larger screen size will not increase resolution per se. JB

 

[Neil McCaulley]

Thanks Jack. So am I correct in assuming that a larger screen does indeed have more physical lines of resolution, but the picture quality will not be better than a smaller screen because it is up to the BROADCAST (source material) to determine the resolution. Kind of like if I watch a movie in 480p. That just means that I am only viewing 480 lines of my available 1080 lines. Correct?

 

[Jeff Gatie]

Yes, the lines or pixels (depending on the display) increase in relative size as the screen size gets bigger. But you also view from farther back as the screen gets bigger, so the relative resolution is the same. This is why we have optimum viewing distances for any given size screen. Also, this is why we can sit closer (thus having a larger field of view, i.e. larger relative screen size) for higher resolution HD content as opposed to regular non-HD content.

 

[Neil McCaulley]

Hey Jeff,

So a larger widescreen TV DOES NOT contain more lines of resolution in it than a smaller TV? My 46" Hitachi has just as much resolution as say a 55" Hitachi?

 

[Jeff Gatie]

In short, no. Although it really depends on the set (not all sets are capable of displaying all 1080 lines of vertical resolution), if a 46" set can display the full 1080, a 51" set (20% bigger) will not have 20% more lines, it will only have 1080. 480, 720 and 1080 are the standards for vertical resolution (horizontal resolutions vary greatly) and a set that can resolve the full resolution for any given format (480 SD, 720p HD or 1080i HD) will have no more than this number of lines (unless they are doing some sort of proprietary upconverting, which is rare).

 

[Neil McCaulley]

I made a mistake. My 46" Hitachi actually has 1,920 VERTICAL LINES of resolution and 1,080 HORIZONTAL LINES of resolution.

In other words, 1080i will look pretty much the same on my 46" at the optimum distance of 10 feet, as it would look on a 55" at the optimum distance of say 12 feet. Correct?

 

[Jeff Gatie]

Yes, all things being equal, they should look the same at the optimim distances.

 

[Neil McCaulley]

Thanks Jeff. It really does get confusing that you have to reverse your logic between horizontal and vertical when you are talking screen resolution. So when anybody is talking 'resolution', they are talking about how many horizontal lines that you can count, stacked on top of one another. Like you illustrated here:

————
————
———— } = 5 VERTICAL resolution lines
————
————

Correct?

 

[Jeff Gatie]

You got it.

 

[Allan Jayne]

The horizontal resolution depends on (among other things) how small a spot can be made on the picture tube. If for a large screen TV the smallest possible spot is larger in an absolute sense compared with a small screen TV, both sets could well have the same resolution.

Note that resolution properly includes a dimension when comparing one TV to another. Technical literature but not all advertising media uses "a distance equal to the screen height" as the reference dimension for both horizontal (dots or upright line segments in a row) resolution and vertical resolution (dots or stacked line segments in a column).

For a particular program, the vertical resolution is at most the number of scan lines (for example 720 for 720p HDTV), and then only if the scan lines as drawn on the picture tube are skinny enough.

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