Why cant a TV display a still image?

Zambini · November 15th, 2006

I have noticed for a while that a TV (crt) can't display a still image without flicker... Why is that?

**drew and not u** · November 15th, 2006

This is because of the screen refreshing itself. It's especially noticeable when the picture is being interlaced (as opposed to progressive scan). Regardless of whether the picture changes, the screen still refreshes, sometimes causing the effect you noticed. With other display technologies (LCDs in particular) though the screen refreshes, the pixels only change when the picture changes.

yurimxpxman · November 15th, 2006

It's more noticeable on TVs than PC monitors because they have lower frequencies, too.

Zambini · November 15th, 2006

Do tv's do like 40hz or something?

My PC does 85 hz. Anything lower I can tell instantly and it gives me a headache

Lead Head · November 15th, 2006

CRT TVs refresh at 30hz. The scan the odd-lines first, then the even-lines. Thats interlaced. Progressive Scanning afaik scans the whole image at once.

The minimum I can deal with CRTs is 75Hz. My CRT does 1360x1024 @ 85Hz. It can do 1024x768 @ 100Hz and 800x600 at 120Hz(with is sweet btw)

yurimxpxman · November 15th, 2006

Don't laugh, but I'm actually running at 60h

Zambini · November 15th, 2006

LO.......

*ahem.

So thats why it is damn near impossible to record a tv's image on a camera... =)

Lead Head · November 15th, 2006

Quote:

Originally Posted by Zambini

LO.......

*ahem.

So thats why it is damn near impossible to record a tv's image on a camera... =)

Thats because most camera's capture around 24FPS, below a TV's 30FPS

Zambini · November 15th, 2006

I meant picto-box, but it makes sense both ways.

LCD's are good to record though :) I always use my laptop to take a picture of a picture.

duckingzebra · November 15th, 2006

i can run mine at 1280 x 1024 (32 bit) at 60 Hz

November 15th, 2006	#1
Zambini Level 2 College Student Join Date: Oct 2006 Location: St. Mere du SantaCruz Posts: 2,036 Blog Entries: 1	Why cant a TV display a still image? I have noticed for a while that a TV (crt) can't display a still image without flicker... Why is that?

November 15th, 2006	#5
Lead Head Join Date: May 2006 Location: Rhode Island USA Posts: 1,716	CRT TVs refresh at 30hz. The scan the odd-lines first, then the even-lines. Thats interlaced. Progressive Scanning afaik scans the whole image at once. The minimum I can deal with CRTs is 75Hz. My CRT does 1360x1024 @ 85Hz. It can do 1024x768 @ 100Hz and 800x600 at 120Hz(with is sweet btw) Opteron 64 165--1.5GB DDR--ECS KA1 MVP(thanks HL!)--x1800GTO 256MB--Seagate 320GB SATA--Antec 550 Watt--Antec P180

November 15th, 2006	#10
duckingzebra SB4L!! Oh..and um..C4L... Join Date: Nov 2006 Location: Las Vegas, Nevada Posts: 232	i can run mine at 1280 x 1024 (32 bit) at 60 Hz Intel Celeron CPU 2.8GHz MS-6714 Mainboard Intel 845G Chipset Intel Integrated 82845G Graphics 40GB UltraDMA Hard Drive Sony DVD/CD RW Steady-state 200 watts PSU

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November 15th, 2006	#2
drew and not u 4GHz or Bust Join Date: Feb 2006 Location: A different kind of Green Computing Posts: 2,005	This is because of the screen refreshing itself. It's especially noticeable when the picture is being interlaced (as opposed to progressive scan). Regardless of whether the picture changes, the screen still refreshes, sometimes causing the effect you noticed. With other display technologies (LCDs in particular) though the screen refreshes, the pixels only change when the picture changes.

November 15th, 2006	#3
yurimxpxman Banned Join Date: Jun 2006 Location: /home/yurimxpxman Posts: 1,695	It's more noticeable on TVs than PC monitors because they have lower frequencies, too.