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1080i + 720p ?


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#1 tony powell

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Posted 02 March 2009 - 06:17 PM

Thoroughly confused by all things HD. Can anyone tell me in simple terms what 720 and 1080 refer to, and which is better to shoot on ?

Thanks in advance to anyone who can help
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#2 Alfeo Dixon

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Posted 02 March 2009 - 07:37 PM

Thoroughly confused by all things HD. Can anyone tell me in simple terms what 720 and 1080 refer to, and which is better to shoot on ?

Thanks in advance to anyone who can help

Very simple. It is the vertical line resolution. NTSC is 480. HD starts with 720 and the next resolution up widely used is 1080. The 'i' stands for an interlaced frame and the 'p' stands for progressive frames.

In terms of which is best, would be relative to your budget and final output. But in most situations, its always a better idea to shoot at the highest quality your budget will allow and scale down.
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#3 Benson Marks

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Posted 02 March 2009 - 07:48 PM

Thoroughly confused by all things HD. Can anyone tell me in simple terms what 720 and 1080 refer to, and which is better to shoot on ?

Thanks in advance to anyone who can help


The most common notation used to describe a format is:

-The number of active horizontal lines per frame (say, 480 or 1080)
-Followed by 'P' or 'I' (for progressive or interlace)
-Followed by the number of scans per second (the frame rate or field rate)

So, a format indicated as 720p/24 tells us that the frame has 720 horizontal lines, scanned at 24 progressive frames per second.

As for which one is better to shoot on, there really isn't one that's better than the other. Some experts argue that 1080i is better because it has more lines of resolution. Why does that matter? As the number of lines goes up, so does the ability to record fine detail in an image, allowing for a sharper, clearer picture. However, other experts argue that 720p is better because 1080i uses interlace, but 720p uses progressive scan, which is considered better than interlace. The problems with interlace include, for starters, that you're seeing only half the lines at a time, which means lower resolution. Interlace creates various artifacts (flaws or irregularities in the image). One artifact is that diagonal lines in the scene can end up looking like jagged stair steps on TV. This is called aliasing. Another artifact called twitter happens when thin horizontal lines appear to vibrate or flicker as they move up or down in the frame. This is often visible in the text of a credit roll at the end of the movie. If you really want to know which one is better, do a comparison between the two formats if you can afford it and decide which format you like best. The question isn't 'Which one is better?' The question is 'Which one is better to you?'
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#4 Rick Martinez

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Posted 03 March 2009 - 01:11 PM

1080 can also be registered as progressive (P). The number 1080 defines lines or pixel and end up determining the frame resolution:

Let's say you are recording at 1920×1080, that imply 2,073,600 pixels per frame or the equivalent to a little more of a 2 Megapixel in a digital photo camera resolution.

From a practical POV some broadcasters use 720p as their primary high-definition format and others the 1080i (which probably will end up being the most used for TV). Progressive is better but there are many legacy technological issues that point to the interlace for the big broadcasters (specially live).

Understand the interlace on the base of dividing the vertical resolution of the frame in two fields that will be broadcast sequentially (1/60 of second for NTSC). One field will contain the even lines and the other the odds which your eye integrate recomposing the whole frame. Interlace creates many quality issues.

If you open many graphic programs they offer the ability to import files as progressive or interlaced. If you choose interlaced need to decide the field order selecting from upper or lower field.

Edited by Rick Martinez, 03 March 2009 - 01:12 PM.

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#5 tony powell

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Posted 06 March 2009 - 05:32 PM

Hi and thanks for your reply. Can you tell me why in that case nobody seems to shoot 1080p if it's possible to do that, as that would surely give the best of both worlds, avoiding artifacts and having a high resolution ?
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#6 David Mullen ASC

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Posted 06 March 2009 - 07:23 PM

Hi and thanks for your reply. Can you tell me why in that case nobody seems to shoot 1080p if it's possible to do that, as that would surely give the best of both worlds, avoiding artifacts and having a high resolution ?


Most high-end HD cameras shoot 1080P, usually 24P or 25P.

But U.S. HDTV broadcast is either 1080/60i or 720/60P, so usually people finish HD projects in one of those two formats for HD release (except for Blu-Ray releases, since you can put 1080P onto that and the player will convert it to play on 1080P, 1080i, or 720P monitors, etc.)

You also have to keep in mind that some smaller HD cameras only record in either 1080i or 720P (and technically, HDV only comes in those two flavors) even if the camera is capturing in 1080P. You record 24P/1080 onto 60i/1080 using a pulldown just as in NTSC.

Another thing to keep in mind that even if the prosumer HD camera offers 1080P recording, it doesn't necessarily mean it has 1080P sensors, it may be uprezzing from smaller sensors, so whether you choose to record that as 1080P, 1080I, or 720P may not matter that much, just depends on how you want to deal with the footage in post.
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#7 Andrew Koch

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Posted 06 March 2009 - 07:42 PM

People absolutely DO shoot in 1080P all the time. Many of the newer hi end HD cameras can deliver this. All of the current super 35 sized sensor cameras can do this (D21, Genesis, F35, Red, etc). Some of the 2/3 cameras can as well (F23, HPX3000, etc). These are just a few. There are several others. Broadcast is only 720p or 1080i, but shooting in 1080p is still a good idea because you benefit from the supersampling. The increased resolution is also helpful when going to film or even blueray. One drawback is that most (but not all) 1080P HD cameras are limited to 30fps. 720P cameras like the Varicam go up to 60Fps giving you the option of slow motion. There can also be some increased light sensitivity with some 720P cameras over some 1080P cameras, but don't quote me on that, ask the experts.

So yes, 1080P is a very viable way to go, but cameras that give you this native resolution are often more expensive.
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