1080i or 720p, which looks better?

[Will Lau]

So what is the consensus on this board? Is 1080i (interlaced, 540 lines visible at one time) or 720p (720 lines visible at one time) better looking than the other? Besides the 3 ccd chip on the new sony, is having 1080i going to improve the image quality against the JVC?

[Peter Moore]

This is a perpetual debate between HDTV fanatics. 1080i has more resolution but only half the picture changes every 1/60th of a second. However, the entire picture changes every 1/30th of a second. Compare this to HDV 720/30p, where the entire picutre also changes every 30th of a second, but the resolution is lower. Also keep in mind that with 1080i, you do see all 1080 lines at once due to residual light imprinting on your eye from looking at the phosohors.

My opinion is that 720/60p versus 1080/60i is a wash, but 1080i is clearly superior to 720/30p so the Sony should be much better than the JVC.

[Will Lau]

So for greater detail, 1080i should look more sharper. But what about motion? Would the 1080i look more video like than the 720 progressvie image? And the 720p more film like, if you can call it that.

[Peter Moore]

Again you have to qualify if you mean HDV 720/30p or HDTV 720/60p.

720/60p would have much smoother motion and be better for sports. 1080/60i would be much sharper when the image is still, but not quite as sharp for motion, though motion would still be pretty smooth. So take your pick there.

720/30p is basically the worst of those three standards. I tend to think 30p does not look film like but merely looks cheap. Personal opinion. So you have neither the smooth motion of 60p, nor the extra sharpness of 1080i.

Thus, sony's 1080i is objectively superior to JVC's 720/30p in my opinion.

[Bill Ravens]

It appears that while 1080i may be visually superior to 720p, playback of 1080i is problemmatic. Any interlaced format doesn't play back well on a progressive display like a computer monitor. In my own opinion, interlace combing on a 1080i image is highly unacceptable and distracting.

[Peter Moore]

Oh quite right. You always want your display to be native to the format you're watching.

Personally I've never been sure how 1080i is converted to 720/60p though this is my guess:

You take 1080 field A, combine it with 1080 field B, gaussian blur, and construct one frame. Then you take 1080 field B, combine it with 1080 field C, blur, frame 2. Etc.

Frame 1: A + B
Frame 2: B + C
Frame 3: C + D
Frame 4: D + E
Frame 5: E + F

etc.

That would give pretty smooth motion while maximizing resolution though you still have to blur a little bit. Another way to do it would be to construct each 720p frame from each 1080i field, upping 540 to 720. This would have VERY smooth motion but would not be very sharp.

[Ken Hodson]

If we are comparing the HD10 and FX1 than that makes it easy'er. The Sony has smoother video. It is also interlaced so it looks like video. The HD10 looks very film like. A little faster than 24p film, but not enough that you can whip those pans.
Resolution they aren't much different. The FX1 has a 960x1080 CCD which it uses green pixel shift (ala XL1) to map out 1440x1080 which is 960(1440 pixel shift)x540 per field.
The HD10 is about 960x720 per frame.

[Scott Anderson]

Ken, I have to disagree with the assertion that the resolutions of the HD10 and FX1 "aren't much different". By comparing one field of the FX1 to one frame of the HD10 is just not a fair comparison. As Peter said, quite rightly, 720p/30 is the worst of the three standards. With your comparison, you could de-interlace every frame of FX1 footage and end up with 720p/60. I don't think that's correct either. The FX1 is designed to shoot interlaced only (as far as we know so far), and displayed that way should look considerably better in all regards than the HD10.

Will, your question reminds me of a display I saw at NAB earlier this year. Windows Media HD compressed content was being shown in a very controlled room, with a high end projector, using footage both from NBC (1080i/60) and ABC (720p/60). Both formats looked awesome, much better and crisper than how film is projected in most theaters. What surprised me was that even the ABC 720p/60 from Monday Night Football looked like video. Even a progressive format at 60 full frames per second seemed "live". Our brains are just hard wired from years of watching TV and movies to percieve slower frame rates (24 or 30p) and longer shutter times as film-like, and higher frame rates as live TV, regardless of whether the frames are progressive or interlaced.

I personally believe the Sony is going to end up looking much better in all important ways than the JVC. Not only will it win on percieved quality with 60 "samples" per second (even if they are interlaced) and higher overall resolution, but the option will be there to use filmlook filters and frame blending software to simulate progressive "looks", even if Sony doesn't offer true 24 or 30p. The JVC is seriously limited by always being stuck in a semi-auto mode, and shooting in the least flexible and inferior of all the HD formats.

[Ken Hodson]

We are talking resolution, not preferable frame rate, and in that regard they are both very similar as you can see by the numbers I wrote. The Sony comes no where near the full 1920x1080.
As far as frame rate I personally prefer progressive in every instance. Your example of 720p60 football looking like video is due to the high shutter speed they use. They are shooting a high motion sport so it makes sense. They want that ultra "live" look, but that doesn't mean it is a deficiency of progressive. You could use a much lower shutter and apply motion blur in post and have it look very film like.

[Peter Moore]

No camera that I know of captures at 1920x1080. I think the Cinealta captures at 1440x1080, right?

[Graeme Nattress]

HDCAM SR does the full 1920x1080, as does the Viper? Either way, HDCAM even at 1440x1080 has more resolution than can be broadcast anyway, and more resolution than most people's HDTVs, so why worry?? Even 1440x1080 looks blinkin good on a full rez 1920x1080 display.

the 960 CCD rez doesn't pixel shift to 1440, but to 1920 instead, which is then down sampled to 1440 I think. Pixel shift will give you real extra luma resolution at the expense of colour resolution. As HDV is a 4:2:0 format it's going to loose a lot of colour resolution along the way anyway, so it doesn't matter that it's loosing it as part of the pixel shift.

The FX1 1080i footage I have converts to 24p in post quite nicely, which is something that the 720p30 footage does not do.

Graeme

[Tom Roper]

The JVC does NOT record 720p30 images in 960x720.

The imaging sensor CCD is 1280x960, and the full width is used to record 16x9 images, 840,000 pixels, 1280x656.

There are 750 scan lines, and 700 horizontal TV lines of resolution.

TV lines of resolution are specified using a circle with a diameter equal to the vertical resolution, thus the actual resolution for the full 16x9 image is 1156x656.

[Ken Hodson]

I'm talking about the actual captured pixel resolution. Of course this is then put onto the "recorded tape format".

Tom -It is widely accepted that the HD10 captures about 960x700 actually it is probably closer to 960x625'ish, which is then recorded to 720p standard (1280x720).
The FX1 captures 960x540 per field which it then uses green pixel shift to increase luma capture 1440x540 per field. With interlace cameras, the effective vertical rez is reduced about 25% so it is actually 1440(PS)x 400 per field or 1440x800 frame.
Sony F950 1920x1080
Panasonic Varicam 960x720
These are the actual pixel captured resolutions. Not theroretical based on CCD or the final tape format resolution.

[Tom Roper]

That's incorrect Ken, sorry. Please post your sources.

[Ken Hodson]

Whats not correct?