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Thin lines and interlacing vs common use of LCD displays

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Paul Berlin
Thin lines and interlacing vs common use of LCD displays
on Aug 8, 2018 at 9:24:30 pm

According to the "Interlacing" section of this:
http://www.tvwithoutborders.com/tutorials/dtv_intro/crash_course_designing_...

Designers shouldn't use thin horizontal lines (less than 4 px wide) because interlaced displays like CRTs won't show them well.

But is this still a concern? Aren’t nearly all displays that people are using (LCD TV or computer monitor, phone or tablet) progressive, so they won’t be interlaced? I think that most broadcast signals are interlaced, but if the display they’re being viewed on is progressive, isn’t this concern about thin lines not valid?


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Dave LaRonde
Re: Thin lines and interlacing vs common use of LCD displays
on Aug 8, 2018 at 10:33:45 pm

How well do you think a 4-pixel-thick line in a 1920x1080 comp is going to show up on a phone?

Dave LaRonde
Promotion Producer
KGAN (CBS) & KFXA (Fox) Cedar Rapids, IA


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Andrew Somers
Re: Thin lines and interlacing vs common use of LCD displays
on Aug 9, 2018 at 2:43:29 am

It's not JUST interlace. lines that are too thin on a *any* monitor will have problems with aliasing, and if moving, jitter/judder.

When we do end credit rollers, we avoid any horizontal lines for this reason.

But as far as interlace, if the signal is interlaced, the monitor will display it interlaced unless it has de-intelacing technology. Of course most modern displays DO. but remember that some people are still using old NTSC sets with adapters. Those 4 lines become two lines in NTSC.

This is not to say that it's a good idea to always design for the lowest common denominator.! I'm pretty sure anyone who is still watching on a down converted NTSC set isn't super concerned about image quality.

But the fact remains, very thin lines can be problematic on displays. Things to consider are contrast, angle, speed if moving, not to mention direction, sub-pixel motion, anti-aliasing available in the system, etc.

If you have a one r two pies line, it is only going to be "sharp" if it is *exactly* horizontal or vertical, and exactly on pixels (not split across pixels). And even the you have to consider what will happen at different scales/resolutions. A two pixel lines in 1920x1080 becomes a 1.333 pixel line at 720. What are you gonna do with that?

Andrew Somers
VFX & Title Supervisor
http://GeneralTitles.com


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Michael Szalapski
Re: Thin lines and interlacing vs common use of LCD displays
on Aug 9, 2018 at 3:20:04 pm

Some broadcast is still 1080i and some is 720p, so going 1 pixel in width is probably not good even if you're not moving it vertically.

- The Great Szalam
(The 'Great' stands for 'Not So Great, in fact, Extremely Humble')

No trees were harmed in the creation of this message, but several thousand electrons were mildly inconvenienced.


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