XDcamEX vs JVC GY HD250

[Joel Chappell]

With the EX1 capable of both 720p or 1080p and others, does that give it an edge over the 250 in this one area? Or does the JVC claim that 720p is here for the foreseeable future, and the ability to easily "uprender" 720p to 1080i have enough merit to even it up a bit?

[David Heath]

If you want 24/25fps motion ("film-look") then the EX should have a big edge theoretically because of the 1080p/24(25). It's when you want 50/60Hz motion that the argument gets more complicated. I don't think anyone will argue 720p/25 is superior to 1080p/25, if you're starting with 1920x1080 chips.

[Thomas Smet]

Originally Posted by Kevin Shaw

Sure there is: full 1080p has 2.25 times the resolution of 720p, which in turn has 2.67 times the resolution of SD video. If you can see the difference between 720p and SD, you'll be able to see the difference between 1080p and 720p on a 1080p display.

And enough of the simulated photo-based examples: either compare footage from actual cameras or wait until someone else gets a chance to do so. Thanks.

At least I try to be honest and back up what I say instead of just saying it with words and convince everybody I am right just because I say so.

Kevin you are thinking with numbers and not with how it looks. Resolution is not everything and the bigger an image gets the harder it is to notice the extra detail. You cannot just say 2.25 times larger and leave it at that because that tells nobody how it will actually look.

Take a 1080i sample and down convert it to 720p. sure you may notice a slight detail loss but not 2.25 times worth of detail is lost. If you do not trust my sample which comes from a higher quality source then if I would have done it with a real 1080i then do it yourself. Sure this is a photo but this test actually gives more of an edge to 1080 since the source is such high quality.

[Thomas Smet]

Originally Posted by David Heath

If you want 24/25fps motion ("film-look") then the EX should have a big edge theoretically because of the 1080p/24(25). It's when you want 50/60Hz motion that the argument gets more complicated. I don't think anyone will argue 720p/25 is superior to 1080p/25, if you're starting with 1920x1080 chips.

Well that depends. My sample shows that while 1080p may have a edge in deatil it isn't a huge edge like some would like to think.

There is also the fact that if you are shooting 24p/25p you will get much better compression compared to the 1080p flavor. 720p 24p uses 2.5 less frames then 60p so the 35mbits used will result in much higher quality compression. The 1080p sample would need a bitrate higher then 60 mbits/s to get the same compression quality as the 720p sample. So sure maybe the 720p will have less detail but it will have better compression. If you are shooting an action movie I would rather use 720p because it should be very hard to break the codec. 720p also has the option of shooting slow motion segments which is something you can't really do with 1080p. I would much rather my film have all it's shots have the same level of detail and stick with 720p for a consistant look then alternate between the two resolutions.

720p 24p/25p gives an artist a lot more creative options and lower compression at only a slight loss at detail.

[Chris Hurd]

Originally Posted by Thomas Smet

...you are thinking with numbers and not with how it looks. Resolution is not everything and the bigger an image gets the harder it is to notice the extra detail. You cannot just say 2.25 times larger and leave it at that because that tells nobody how it will actually look.

This is indeed the truth, and it is a fundamental concept that is the mission of this site to impress upon all who visit here. I try to go out of my way to promote this single fundamental understanding to everyone who wanders through this site.

It's never about the numbers, it's only partially about the numbers, and numbers always take a back seat to how the image actually looks; plus there are other factors that need to be considered such as viewing distance for example... there is a point where the viewer's distance from the screen renders moot any difference in "resolution." Thanks Thomas,

[John Bosco Jr.]

Originally Posted by David Heath

Timing is also important, with HD broadcasting becoming a reality far earlier in the States than most of the rest of the world (except Japan).

Screens with 1920 horizontal resolution have only become a reality at sensible prices in the last year or so, and same with cameras - for 60Hz standards, HDCAM is 1440 horiz, DVCProHD (1080) is 1280. Only now is 1080 starting to mean 1920, if you like. So the networks arguments may well have gone along the lines of "why go with a format whose undeniable advantage (horizontal resolution) can't really be taken full advantage of in practice?"

True. However, broadcast stations knew what they were getting into with HD as Sony and Panasonic demonstrated the two options, 1080i and 720p, on full HD monitors, 1920 x 1080i and 1280 x 720p. In fact, the monitors were CRTs. Panasonic later demonstrated 720p on huge motion picture like video screens and Sony on plasma. However, what was not known at that time was the broadcast of 720p 60, 720p 30 was the standard. I still don't think that would have changed the network's view on which standard to go with.

[John Bosco Jr.]

Originally Posted by Thomas Smet

Well that depends. My sample shows that while 1080p may have a edge in deatil it isn't a huge edge like some would like to think.

There is also the fact that if you are shooting 24p/25p you will get much better compression compared to the 1080p flavor. 720p 24p uses 2.5 less frames then 60p so the 35mbits used will result in much higher quality compression. The 1080p sample would need a bitrate higher then 60 mbits/s to get the same compression quality as the 720p sample. So sure maybe the 720p will have less detail but it will have better compression. If you are shooting an action movie I would rather use 720p because it should be very hard to break the codec. 720p also has the option of shooting slow motion segments which is something you can't really do with 1080p. I would much rather my film have all it's shots have the same level of detail and stick with 720p for a consistant look then alternate between the two resolutions.

720p 24p/25p gives an artist a lot more creative options and lower compression at only a slight loss at detail.

That is the best argument yet for 720p, and considering that U.S. broadcast TV compresses to 19mb/s using long GOP MPEG 2, compression artifacts will have some impact. Good point.

Of course, I don't know how we got started on 1080i vs 720p as the EX 1 shoots both.
I believe the EX 1 is a better camera than the JVC 250 because mainly of the sensor size and higher bit rate. I feel the 250 is overpriced for what it is.

[David Heath]

Originally Posted by John Bosco Jr.

True. However, broadcast stations knew what they were getting into with HD as Sony and Panasonic demonstrated the two options, 1080i and 720p, on full HD monitors, 1920 x 1080i and 1280 x 720p.

Maybe, but at the time the decisions were being made, full HD monitors weren't even available for consumers, and that possibility seemed in the very far future. Now they are close to being the norm. Hence, even if a difference was seen, it would be quite understandable for it to be ignored on the basis that it couldn't be noticeable to any consumer. Which until recently has been true.

But I agree with previous posts that too much shouldn't be read into some network decisions, they are not always made for the best technical reasons.

[Kevin Shaw]

Hey gang, the EX1 will be shipping in a few days and we can start looking at some actual footage to compare that, instead of speculating about it based on technical specs. :-)

Does Blu-ray support 720p playback at 60 fps?

[Tom Vaughan]

Originally Posted by Kevin Shaw

Does Blu-ray support 720p playback at 60 fps?

Yes, it does... encoded in MPEG-2, VC-1 or AVC (H.264).

Tom

[Werner Wesp]

uprezzing 1080i50 to 1080p50 of a scene with (a lot of movement) asks for deinterlacing first. Therefore yielding a lower quality 1080p50 compared to 720p50 uprezzed. If the original 1080i footage isn't interlaced first you'd get jagged edges on movement.

Anyhow, I do a lot of people get me wrong. interlacing is a very nifty trick. It solved the original problem of tubes years and years ago for instance. It is just an old fashioned standard nowadays with virtually no benefits, since all flat panel TV's and monitors are natively progressive. They do accept 1080i, but have to deinterlace it to show it on their screen. interlacing is only seen in full quality on CRT's and that's whats in the screen technology natively.

Since virtually all equipment is progressive, codecs are adapted to progressive better and so on, why retain the old standard that was only invented because TV's couldn't handle full images at onces (i.e. progressive)? How many that have a 1080i camcorder actually have a 1080i capable CRT monitor, I wonder...

The mathematics are simple enough, I don't have to repeat them. 720p50 packs over 46,0 million pixels per second - 1080i50 packs theoretically just under 38,8 million pixels per second*. I know what footage I'd like to have on my NLE, especially if I want to do a lot of time-stretching effects.

* in reality it is even less, because if 1080i resolved all 1080 lines, horizontal details of 1 pixel thick would cause severe interlace flicker. To avoid that and keep the image steady, the interlaced smears details out over several lines - resulting in a small gaussian filter effect - working out to a resolution loss of about 30%. More realisticly, 1080i50 packs just over 28,0 millions per second.

All this combined makes it difficult to believe 1080i is still here. Although, why would sony have 1080i only on older models and on recent models also the capability of 720p?

720p and 1080i are both standards that'll be lost soon enough and make way for a 1080p50/60 standard, but in the meantime, I'd suggest shooting in 720p50/60 and if you really want 1080i50/60, you can always DOWNsample your original 720p50/60 to 1080i50/60...
(720p50 to 1080i50 is indeed downsampling 46M to 28M pixels per second)

[David Heath]

All absolutely true if you need 50 or 60 Hz motion. But for most drama etc, 25Hz motion is chosen for aesthetic reasons, and then we're not talking about 1080i/25, but rather 1080p/25. But yes, the sooner 1080p/50 sweeps both 1080i AND 720p away, the better.

[Werner Wesp]

Originally Posted by David Heath

All absolutely true if you need 50 or 60 Hz motion. But for most drama etc, 25Hz motion is chosen for aesthetic reasons, and then we're not talking about 1080i/25, but rather 1080p/25. But yes, the sooner 1080p/50 sweeps both 1080i AND 720p away, the better.

True, since 1080p24, 25 and 30 is possible, that is superior to 720p24,25 or 30. What the camera will deliver in those modes remains to be seen, but 1080p the best you'll get if the camcorder can deliver it and the desired frame rate for your purpose is available in that mode.

[Kevin Shaw]

My understanding is that the EX1 has a 1080p recording mode, so if it maintains full resolution at that setting it should look pretty good compared to the JVC cameras. And there are other reasons to expect the EX1 to be stiff competition, so it's not just about pixel counts and frame rates.

[Thomas Smet]

I have done a few tests now with motion video. I have created many samples of animated video including simple fast moving objects and scenes that have a lot of 3D rendered hair and fur. In the end with proper filtering the 1080i versions and the 720p both playing back upscaled to 1080p 60p look almost exactly the same. I would share these samples but I cannot think of a way to share 1920x1080p 60p video with you guys. All the tests I have done were in special playback software I wrote so it could run the video at 60p.

I would say the 1080i was about 1% sharper which was kind of an illusion really. The reason why it looks sharper is because of the interlacing. Because the video is interlaced you end up with 1080 unique lines of detail that are all different. With progressive video the lines tend to blend into each other making a more natural looking image. With interlaced however you do not see this blend as much because of how the fields are split. 1080i does work very well for HD and while there can be edge artifacts they do not show up as much as some would think. 1/60th of a second is pretty fast and before you could notice anything missign the missing part is replaced with the next field and so on. The beauty of 1080i however is that even when you have a single field it still looks like a 1080 image. A single field with the lines alternating will look much sharper then a 1920x540 rendered image so you cannot say 1080i only has 1920x540 per field. Sure it has that many pixels but they are spread out better so they look more detailed.