1080i VS. 720p

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kat.hayes

Active member
I am still fairly new to all of this, so thank you for your patience in advance.

From what I understand, 1080p results in better quality than 1080i or 720p. Though 720p looks better then 1080i.

1. Why doesn't the HVX have 1080p? Is it an issue of keeping it in a certain price range or is there some technical reason?

2. Are there any guidelines for determining when to shoot in 1080i vs 720p?

Thank you!
 
You can shoot 1080 24p or 30p which is a progressive signal recorded in a 60i stream (this was done for legacy reasons and NLE compatibility). The only downside to recording progressive in a 60i stream is it takes up more space on the p2 card than 720 24pN. You would only shoot 720p over 1080 24p if you wanted to overcrank (for slow motion effects) or you wanted to conserve space on the p2 card.
 
Remember that your footage is going to be shown on the full spectrum of good and bad video devices and DVD set tops.

For the money, the value lies in 720/24pN
 
kat.hayes said:
Why doesn't the HVX have 1080p?
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It does.

2. Are there any guidelines for determining when to shoot in 1080i vs 720p?
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You'd shoot 720p when your targeting your work for display/broadcast on a 720p network, for one. Or when you need variable frame rates. Or shooting high-action stuff like sports, 720/60p is exquisite for that.
 
Genuine 1080p isn't widely supported as it requires bandwidth that exceeds the spec of the most widely used HD-SDI interfaces. However that spec has been revised, and support for 1080p is theoretically possible now, it's just a matter of waiting for existing equipment and infrastructure to catch up.

In the meantime, most 1080 progressive footage is carried on an interlaced signal (in the same way that Standard Def progressive video is). This is technically known as 'PsF' - progressive segmented frame (sometimes referred to as progressive scanned frame).
 
Well, "PsF" is a Sony implementation of recording progressive footage in an interlaced stream; it doesn't refer to the general method of carrying progressive in an interlace stream, especially as it's been implemented since the first days of showing 24 fps material on an interlaced TV screen . . . that's called "pulldown."

"PsF" is something specific to Sony.
 
I love it when the retail box stores tout 1080p plasmas, etc

I always asked what stations are available in 1080p.
 
sycophant said:
Genuine 1080p isn't widely supported as it requires bandwidth that exceeds the spec of the most widely used HD-SDI interfaces.
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Surely that depends on the frame rate? It may be true for 1080p/50, but not 1080p/25.
David Jimerson said:
Well, "PsF" is a Sony implementation of recording progressive footage in an interlaced stream; it doesn't refer to the general method of carrying progressive in an interlace stream, especially as it's been implemented since the first days of showing 24 fps material on an interlaced TV screen . . . that's called "pulldown."
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Sony may well use the terminology, but it doesn't specifically refer to any unique implementation by them. The BBC have produced what many regard as an excellent general handbook on HD ( http://www.bbc.co.uk/guidelines/dq/pdf/tv/HDBookv01_02.pdf ), and on page 12 they say:

"When progressive images are handled for transmission, at less than 50 frames a second, they have to be sent in two parts (fields) to avoid the annoying flicker. This is known as Progressive with Segmented Frames (psf). It is exactly the same process as is used for scanning film (at 25 frames per second) for conventional transmission, and is a key element of the film style image."

Psf techniques are used for most current HD broadcasting in Europe (as 1080psf/25), that includes the BBC, and does not necessarily involve Sony equipment or techniques. The remainder (where motion rendition becomes more important) are mostly 1080i/25. But whilst Psf is used quite extensively in 50Hz countries for broadcasting, "pulldown" refers to techniques used in 60Hz countries to show 24 frames within 60 fields.
 
But there IS a pulldown in 50i if you're transmitting material at 24 fps, instead of speeding up 4% to 25 fps. I recognize that this is often not done for television, but it does come into play when watching 24p DVDs, for example, on a PAL system.

As for the PsF, you may be correct to its generality; I really hadn't seen it referenced as being used by anything other than CineAlta gear, and others have said it's a Sony implementation. Mea Culpa.

But my point really was, PsF isn't the same as pulldown and shouldn't be confused with it . . . and it especially shouldn't be referred to as "Progressive Scanned Frame."
 
David Jimerson said:
But there IS a pulldown in 50i if you're transmitting material at 24 fps, instead of speeding up 4% to 25 fps. I recognize that this is often not done for television, but it does come into play when watching 24p DVDs, for example, on a PAL system.
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Yes - true point. Though as you say, it is far less common than simply doing a 4% speed change. A 3:2 pulldown is one thing, but turning 24 frames into 25..........AFAIK it gets done very rarely.

I'm also not sure what happens with 24p DVDs in the 50Hz world. I suppose I'd assumed they just got treated in the same way. Thinking about it, I don't believe they actually exist as such - region 2 film DVDs I believe have been telecined at 25fps, and probably exist as 576psf/25 on the disc. Hence they are immediately compatible with other PAL equipment, and a suitable player can resurrect a true 25p signal from them.

HD discs are different, and I think how they get treated depends on the individual player and display.
 
A DVD can be encoded with 2:2:2:2:2:2:2:2:2:2:2:3 pulldown flags in order to play back 24fps material without speeding it up 4% -- this is generally useful for things like musicals where the speed can make a difference in the music.

Our DVDs are region-free but 23.976p; they play fine on Region 2/PAL DVD players.
 
David Jimerson said:
Our DVDs are region-free but 23.976p; they play fine on Region 2/PAL DVD players.
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Hmmm. You've got me wondering now about what comes out of the output of such a player. If they're region free that obviously won't be an issue, but I seem to recall my DVD player has a PAL/NTSC/Auto output menu option, and it would normally be set to "Auto". In that case, I'd expect a standard NTSC output with 3:2 pulldown (most TVs here will happily accept NTSC inputs), but it's got me wondering what would happen if I forced the output to "PAL"?
 
What is the best shooting (resolution, scanning) setting if the feature movie is going to be shown on a big cinema screen, using 1080 HD projector, is then 1080/25p better then 720/25p.
 
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