To Over Scan or Not to Over Scan

Quryous wrote on 3/27/2006, 10:28 AM
I have been reading a lot of info on this forum advising people about the "Normal" overscan on a TV. One comment in particular was to not worry about the bottom 5 or so lines if they were blurry because that would be lost in overscan. That I can understand, but ONLY to a point.

On a CRT, or rear projection TV, this makes sense. Some of the info is lost all the way around the frame.

BUT, when the picture is viewed on an LCD, Plasma, or similar flat screen, is there actually this lost area we so fondly think of as overscan? Does it exist?

TV is fast abandoning the CRT in favor of LCD, Plasma, etc. I thought that with them the image was a FULL image, not one chopped off all the way around as on a CRT.

What say you?

Should we be planning on a day when there is no such thing as overscan?

Comments

Former user wrote on 3/27/2006, 10:51 AM
My opinion is we will always have some overscan. No one wants to see the time code, caption information and other junk that is in the top and bottom of a screen. Currently captioning is on line 21 of the NTSC video. This is in the active area of the video image.

Until this information is translated digitally as well, I think overscan will be a blessing.

Dave T2
Quryous wrote on 3/27/2006, 11:22 AM
You seem to be talking about something that is not seen on ANY set, LCD, CRT, Plasma, or other, under normal circumstances. I am talking about the part that we sometimes call the "Safe Area."

Is THAT going to be something that is normally seen on all future LCD, Plasma, etc. type screens? That is the part that is lost on a typical CRT, right? But is it on the LCD, Plasma, Etc.?
riredale wrote on 3/27/2006, 11:25 AM
To my knowledge, there is no overscan on a video image as seen with WinDVD or PowerDVD, so yes, it's important to plan ahead.

In my own case I often use Deshaker to smooth out handheld shots. Deshaker has a nifty feature where it will attempt to fill in the black boundaries of frames that have been shifted slightly; even so, there is sometimes some distracting "junk" left at the edges of the active area. I use a 4% black mask (via Cookie Cutter) all around in order to cover up most of this clutter.

Incidentally, we have a 62" Mitsubishi DLP rear-projection monitor in our living room. I had assumed originally that there would be no overscan, and was surprised to find that it overscans about 7%.
Chienworks wrote on 3/27/2006, 11:32 AM
The Eiki LCD video projector in our church has about a 3% overscan.
Former user wrote on 3/27/2006, 11:55 AM
"You seem to be talking about something that is not seen on ANY set, LCD, CRT, Plasma, or other, under normal circumstances"

Not really. If you see FULL SCAN, meaning the whole picture, you will see all of the information I mentioned. Like I said captioning and TC are in the active area of the image.

Dave T2
rs170a wrote on 3/27/2006, 2:21 PM
...captioning and TC are in the active area of the image.

DaveT2, I have to disagree with you on that. As I recall, the active area (defined as the beginning of display video) doesn't begin until line 26. I'll check some of my old textbooks to confirm that though.

As far as the OP's question goes, I was curious about that issue too so I asked the president of my local SMPTE chapter, thinking that there may be a new safe action area/safe title area standard.

Q:
With all the new display devices coming out these days (plasma, LCD, projection, etc.), is overscan still an issue like it was in the "old" days?
i.e. 5% safe action & 10% safe title?

A:
I'm not aware of a new "standard" as such, though I have seen 16:9 finders with safe action/title graticules that look like they're about the regular 10 and 15 percent
crops as with standard def and 4:3.

It appears as though most new displays are set up with very little crop or overscan,
probably to make full use of whatever native pixel resolution is available.
A couple of plasmas at my bank that display computer generated news tickers, etc. drive me crazy. One is set quite severely overscanned, so as to cut off near-edge
material, while the other one is about 15% underscanned, so there's black
around everything.

My personal view on "safe area" has always been - If something is visible in the frame, many people will not see it but, someone, somewhere, IS going to see it (like boom mikes, edges of stage flats etc).
If something is within the customary "action safe" area, nearly everyone will be able to see it.
If something is within the customary "title safe" area, everyone will see it, unless their equipment is severely out of adjustment.

Mike
Former user wrote on 3/27/2006, 3:19 PM
The display video starts at line 18. CC is on line 21. TC is on line 19 or 20 I think.

When capturing analog through my capture card, many times I can see the captioning.

Dave T2
rs170a wrote on 3/27/2006, 5:54 PM
The display video starts at line 18.

I'm pretty sure it's line 20 but my reference book is at work.
Lines 17 - 20 are reserved for various test signals, cue and control signals and identification signals.
You're correct about CC being on line 21 which is why you see it.

Mike
Former user wrote on 3/27/2006, 6:25 PM
Technically line 22 is considered the first active line of video. An analog or digital NTSC vcr can be set to blank from lines 18 to 22. Lines 18 through 22 can be broadcast and seen on TVs that show the full scan. These areas are normally used for VITC, Closed Captioning, encoding for tracking and even sometimes copyguard measures. They can be seen on some TV broadcasts on a TV that shows that area. They have to be seen for the decoding boxes down the line to interpret them.

But they are all active video areas.

Dave T2
rs170a wrote on 3/28/2006, 5:32 AM
The RS-170 A spec says:
First full active line line 21, field one
half-line 20, field two.

Reference 1 (GIF image)
Reference 2 (Tektronix Appliction Notes PDF - Section 7 - p. 71)

Mike
Former user wrote on 3/28/2006, 5:57 AM
I appreciate what you are saying. The technical specs state that line 20 and 21 (field two and one) are the beginning of "active " video.

The reality is that when you see full raster video, you may see as high as line 14 or 10. If your TV has extreme overscan issues, you can see VITC (lines 10 or 14) as well as other trash thrown in these areas. These lines can be used for pulses that allow for tracking spots or programs by companies like Nielsen. So this information has be to passed by broadcast facilities.

So yes, video is supposed to start at 20. But you can see far beyond that on a full screen video.

Dave T2
Quryous wrote on 3/28/2006, 10:23 AM
Somehow I don't think we are talking about the same thing. When I look a a CONSUMER LCD TV, or Consumer Plasma TV, I see one heck of a lot more information around the edges than on any glass tube CRT TV on the display floor.

I don't think any of these things are full screen displays in the sense that they show all those normally invisible scan lines. But, they show MORE of what was the normally lost area.

Never seen those invisible lines. Hmm!
rs170a wrote on 3/28/2006, 10:40 AM
Somehow I don't think we are talking about the same thing.

I think you're correct. DaveT2 and I got caught up in underscanned image definitions (i.e. seeing all 525 lines - right Dave T2??)

What you're seeing is that the new displays are showing you more of the image, i.e. less overscan. A decent new CRT TV will be almost as good. For example, I've got a 15 yr. old (at least) 27" Sony Triniton at home and it wasn't until this past year that I really began to notice it overscanning more than it normally did.

The SMPTE spec for safe action & safe title areas calls for 5% & 10% respectively. 30 or 40 years ago, this was a tough spec for most TVs to meet. Today, with (hopefully) tighter quality controls, it's a lot easier.

As others have mentioned here, the underscan/overscan issue will probably be with us for some time yet so it's always a good thing to compensate for, especailly when you're shooting.

Mike
Former user wrote on 3/28/2006, 10:57 AM
Quryous ,

We are talking about the same thing. The original question was about cutoff. With the new PLASMAs and such, there is still some cutoff. There needs to be in order to avoid seeing the above mentioned "invisible lines". Remember the 5%, 10% action/safe areas are more guidelines than rules. No manufacturer has ever been consistent on what the TV frame cuts off of the actual TV signal. You can see that by going to a TV display area and comparing TVs of the same model and make. You will notice that each shows a little different area of the edges.

My original point was, you do not want to see all of the broadcast video image. Cutoff is a good thing in most cases. How much is cutoff is the concern.

Dave T2