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JVC GY-HM 70/100/150 Series Camera Systems
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Old July 27th, 2009, 03:20 AM   #31
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While I look for my slides: It seems then the 1280x720 chips are always pixel-shifted to obtain 1920x1080. JVC is assuming that a 50% increase in resolution is possible. I would expect dynamic (moving) measurement to show more like a 15% increase on both axes.
I can vouch for that. My tests have shown that while there is greater resolution in 1080 mode, it is certainly not 50% greater than in 720 mode. 15% would be about right.
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Old July 27th, 2009, 03:26 AM   #32
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1080 vs 720 and i60 vs p30

OK, my two cents here.

Before I made a final decision about HM100 I did a lot of test and look it on my Panasonic plasma HDTV (full set up to native 1920x1080p60). I made video of some water sport with intensive ball moving under different shot modes and compared picture from camcoder->HDMI->Panasonic. I decided that 1920x1080i60 is the best for sport mode because it shows a very smooth ball movement and it also shows a pretty good overall picture, resolution and color.

Later I established a framefork with NLE on my notebook and I unexpectedly discovered that 1920x1080i60 is not the best! I turned back and did a couple of additional comparisons to solve a puzzle.

Skipping details I want to say that comparison should be done carefully.

1) Don't use LCD for comparison of fast moving picture (just remind) - many of them have a long pixel light time and it produces a "traceable" picture of moving objects. In this case p30 looks better just because it lights little less pixels. It even may look better then p60!

2) Don't compare interleaved shots with progressive in computer monitor. Computer monitors have progressive output today and that it especially true for LCD. The typical video player in computer doesn't do a good de-interlacing job and picture looks with interlacing jadder amid with poor moving object boundaries. After I applied de-interlacing filter in Vegas Pro with _interpolate_fields_ de-interlace method the result looks much much better and reminds me a video on my Panasonic. Before de-interlacing progressive shots looked better than any interlaced. The same is actually for any HDMI output from computer to HDTV if computer graphic board supply progressive 60 - the interlaced picture looks much worse that the same shot from HM100 directly.

3) High resolution large plasma HDTV is able to cope i60 much better but I don't know how - does it use a field type of screen like a regular SD TV or has a good real-time interpolation filter.

Finally I stay on my initial decision - if you want a shot for HDTV (not film and not BlueRay disk) then the best is 1920x1080i60 for high lights.

Would 1920x1080p60 be better than i60? It is a tricky question - p60 leaves less exposition time for CCD pixels and the final picture would be more noisy. I think doing i60 CCD is able to provide much more efficient pixel shift process and increase resolution on the same CCD size too.
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Old July 27th, 2009, 03:50 AM   #33
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With flat-panels -- electronics must convert 60i to 60p. With motion this can NEVER be done correctly.
Does this explain the flicker I have seen on my HDTV with 1080i footage such as blades of grass that exhibit a lot of highlights and lowlights? I noticed while watching scenes that have a lot of fine detail that there is this flicker that often occurs. It usually only occurs when the camera is handheld and being held reasonably stationary but involving a small amount of movement; when the camera is panned the flicker goes away. I have noticed this in the 1080i mode. I haven't done tests in the 1080p mode. The TV I was watching it on is a Sony Bravia, 46". Whether I shoot in 1080i or 1080p, it only ever sees an interlaced signal from the camera. This is not the case with 720p footage.

Leonid, thanks for your input. However you talk about 1080p60, which does not exist with this camera. Did you mean 1080p30?
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Old July 27th, 2009, 11:41 AM   #34
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Leonid, thanks for your input. However you talk about 1080p60, which does not exist with this camera. Did you mean 1080p30?
No, Actually The last sentence was a generic, what could happen if JVC supports p60 on the same CCD chip size and how could it compare with another shot modes. Just note about engineering difficulties, nothing more.
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Old July 27th, 2009, 12:06 PM   #35
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I can vouch for that. My tests have shown that while there is greater resolution in 1080 mode, it is certainly not 50% greater than in 720 mode. 15% would be about right.
I would also back this up on the HM100.
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Old July 29th, 2009, 03:46 AM   #36
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Does this explain the flicker I have seen on my HDTV with 1080i footage such as blades of grass that exhibit a lot of highlights and lowlights? I noticed while watching scenes that have a lot of fine detail that there is this flicker that often occurs. It usually only occurs when the camera is handheld and being held reasonably stationary but involving a small amount of movement; when the camera is panned the flicker goes away. I have noticed this in the 1080i mode. I haven't done tests in the 1080p mode. The TV I was watching it on is a Sony Bravia, 46". Whether I shoot in 1080i or 1080p, it only ever sees an interlaced signal from the camera. This is not the case with 720p footage.
If you see it only with interlace you are seeing ""interlace twitter."." When handheld, a camera moves up and down over fine detail so it appears in one field but not another. When a detail only exists in ONE field, it is displayed every other field time, so it flickers at 30Hz.

When you pan up-down fine detail (brick) the horizontal detail becomes alive with "interlace twitter" which is caused by the same alternating field problem.

Frankly, I am always puzzled by why folks praise the higher resolution of 1080i and yet seem not to be bothered by "interlace flicker/twitter." Perhaps this is one reason way Varicam is so loved by filmmakers. Film doesn't have this type of artifact.

At NAB 2008 Sony showed me 1080p60 on their OLED display. WOW! This is the future! And, given the sensor/DSP already works with 1920x1080 at 60p -- I wonder what it would take to record it. It's not impossible. Sanyo already sells a $700 1080p60 camcorder!
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Old July 30th, 2009, 03:11 PM   #37
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If you see it only with interlace you are seeing ""interlace twitter."." When handheld, a camera moves up and down over fine detail so it appears in one field but not another. When a detail only exists in ONE field, it is displayed every other field time, so it flickers at 30Hz.

When you pan up-down fine detail (brick) the horizontal detail becomes alive with "interlace twitter" which is caused by the same alternating field problem.

Frankly, I am always puzzled by why folks praise the higher resolution of 1080i and yet seem not to be bothered by "interlace flicker/twitter." Perhaps this is one reason way Varicam is so loved by filmmakers. Film doesn't have this type of artifact.
Actually, I am surprised that you can see any flicker on TV. TV - and HDTV too - was designed to keep the upper field on screen sometime during low field is displayed. That was because of CRT pixel light latency - the CRT phosphorous had some light time after electron beam hits it. And the time was designed to keep upper field pixels lighting during update of low field pixels and vice versa. That helps increasing screen brightness. And that can be true for many plazma HDTV for the same reason.

Again, I guess that flicker may happen because player-HDTV pair shows the progressive picture based on cheap reconstruction of two fields (upper and low) of an interleaved shot. In this case you may see bright pixel from upper field which comes dark during next frame reconstructed from low field. That was a primary reason why I recommend to avoid looking i60 in progressive mode. Only after rendering interleaved shot to progressive it has sense. It is actually inexpensive in CPU time, at least in Vegas Pro (unfortunately, I have not a serious experience with other NLE).
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Old July 31st, 2009, 04:51 AM   #38
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A stringer nearby shoots football on his $10K HD, and the vision looks CARP. The images are so juddery its not funny. Its a visual staccatto that is quite nauseating to watch and grossly out of place.

My gut feeling is he cant switch the camera to shoot interlaced... Would that fix the problem?

Ben
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Old July 31st, 2009, 06:20 AM   #39
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A stringer nearby shoots football on his $10K HD, and the vision looks CARP. The images are so juddery its not funny. Its a visual staccatto that is quite nauseating to watch and grossly out of place.

My gut feeling is he cant switch the camera to shoot interlaced... Would that fix the problem?

Ben
Of course. As would shooting at 720p60.

But, what some call horrible judder, other call the look of film. Moreover, the flight of a ball wouldn't have judder since the shot would likely be wide and so the motion vector of the ball would be small.

Because filmakers take care about shooting motion they minimize judder. I really don't want to leave the impression that low frame-rates can't be used. Of course they can. But, one needs to be aware.
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Old July 31st, 2009, 09:40 AM   #40
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In preparation for shooting a project involving small waterfalls which will go out to SD-DVD I have been experimenting with various camera settings (HPX170). My objective was to achieve maximum detail and realistic motion. Here were my test results outputing to DVD with playback on 32 and 40 inch HDTVs.

720/30pn, 1/60 - poor detail in water flow
720/60p, 1/60 - better
1080i, 1/60 - best with very smooth yet sharp motion

I had originally wanted to shoot progessive so as to utilize the HPX170 slow - motion capability. Anyone have any suggestions to improve progressive look with this subject matter.
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Old August 5th, 2009, 09:35 PM   #41
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Frankly, I am always puzzled by why folks praise the higher resolution of 1080i and yet seem not to be bothered by "interlace flicker/twitter."
Steve, thank you for saying it, and I'll second it. "Death Before Interlaced" is my motto. I even cover soccer and other sporting events in 24p because I think it makes a better DVD transfer than anything else when viewed on a HDTV. (though I could capture 60p at 1/60th and use in a 24p timeline and have the 60p as a source for nice slow motion instant plays.... but that just means more work. Just pan with the action with 24p and everything is fine. I mean no one complained about judder in TITANIC or TERMINATOR 1 & 2 or any movie I remember (other than BLAIR WITCH PROJECT). You just have to be a better camera operator and really keep the shutter at 1/48th or if you have to 1/60th. But I know many films have gone over 1/500th on a static shot (before SAVING PRIVATE RYAN) because they didn't bring enough ND filtration with them.
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Old August 7th, 2009, 12:27 AM   #42
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Steve, thank you for saying it, and I'll second it. "Death Before Interlaced" is my motto. I even cover soccer and other sporting events in 24p because I think it makes a better DVD transfer than anything else when viewed on a HDTV. (though I could capture 60p at 1/60th and use in a 24p timeline and have the 60p as a source for nice slow motion instant plays....
I tend to get distracted by what SHOULD NOT be in an image. Back in the Hi8 drop-out days glitches drove me crazy, yet when I taught a video class in Japan I had to really work to get people to see them. (Perhaps living in a crowed world enabled folks to be better at not being distracted.) Perhaps Sony honestly didn't think the glitches were a problem! :)

I think it is the artifacts of video we have learned to live with that drives film folks nuts. Things like edge enhancement that would never be found on film.

Of course, dust in the film gate drove me nuts -- so perhaps it purely individual as to what folks find objectionable. In which case, camera reviewers may need to share their biases as part of their reviews. It's my visual bias that agrees, ""Death Before Interlaced."
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Old October 2nd, 2009, 12:18 PM   #43
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Two questions... (all numbers are for Europe.. 30 and 60 should be for USA)

1) Does the CCD size count when panning in progressive 25p? Will (at same frame rate/shutter) there be a difference with a 1/3sensor or a 2/3 sensor ?

2) In TV shops they sell 100Hz and 200Hz LCD and LED TVs that create missing frames from 24p BluRays and also DVDs. I can see even old movies with an incredible quality and frame smoothness. How do they do the trick? Also.. I remind.. LCDs don't have "real interlaced" (electronic pen drawing first upper lines then lower lines) but what they do really is create 50 full frames from 50i. For example ... I've been told some TVs have a realtime circuit that can create a 1080/50p stream from a 1080/50i stream by interpolating in this way...
Let's say I have 1ul, 2ul, 3ul, 4ul, etc.... They create (1u+1l), (1l+2u), (2u+2l), (2l+3u), etc... In this way.. sure they interpolate but they have 2 different "full" frames from every single 50i frame and they can have a 50p stream from a 50i signal.
Is it possible that I cannot find any plugin/software etc.. that uses a similar process to change my 1080/50i into a 1080/50p and not a 1080/25p ?

.. still.. I don't understand what 100Hz and 200Hz TV set do ?!!
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