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Old December 4th, 2005, 10:31 AM   #1
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How are the HDV artifacts on this camera?

I've read very little on this topic. I'm aware of the camera's other problems, but what I really want to know is how JVC's 720p HDV holds up compression-wise.
Does the image go soft on pans so it looks almost like a slow shutter effect, like Sony's HC1? Does macro-blocking rear it's ugly head? What, if any, artifacts show up with the shorter 6 frame GOP?

Thanks, guys.
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Old December 4th, 2005, 11:45 AM   #2
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The JVC has the cleanest implementation of all the HDV cameras. It's substantially cleaner than the Sony version. Of course, part of that is due to it recording only 30 frames per second (or 24), so it's not a direct apples-to-apples comparison -- the Sony is pushing about twice as many pixels per second through its codec, which gives it higher temporal resolution, and an increase in susceptibility to macroblocking etc.

But as far as looking for glitchy garbage in the footage, the JVC is the cleanest of the HDV cams. Especially in 24p mode. The less data you ask it to handle, the better it's able to cope, and 24p encodes 20% fewer frames than 30p.

Can you get it to "break"? Yes, but you really have to work at it -- a lot of high-contrast fine detail for example. I've also seen some odd quilting artifact in a JVC demo shot of a zoo, where they were pointing the camera down at a swimming penguin and the rippling water caused a codec overload. But those aren't common situations. In common situations the JVC looks pretty solid.
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Old December 4th, 2005, 12:15 PM   #3
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My personal experience with the camera (roughly a week now) has proved to be great. I have seen little to no noise, even in low light and as for the compression... very, very clean.

The only thing I have noticed is that if I focus on something (near the end of the telephoto) and then rock the focus back and forth, I get a slight green hue with my blurred image to one side and a blue hue when I defocus to the other side. Am I being clear enough here? I zoom, then focus and then pull it out of focus both directions and get the blue or green hue.

Something related to the CCD's and how they handle the defocused colors?

I could maybe post an example if no one has seen this before.
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Old December 4th, 2005, 01:41 PM   #4
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Quote:
Originally Posted by Daniel Patton
The only thing I have noticed is that if I focus on something (near the end of the telephoto) and then rock the focus back and forth, I get a slight green hue with my blurred image to one side and a blue hue when I defocus to the other side. Am I being clear enough here? I zoom, then focus and then pull it out of focus both directions and get the blue or green hue.

Something related to the CCD's and how they handle the defocused colors?
Its called Chromatic Aberration and it is a characteristic of the cheap lens elements. Low dispersion glass and flourite elements (like in the Canon XL2 stock lens) help reduce "CA." The problem is much more prevalent in CCD than film because the light must enter the CCD at a much more precise angle - especially when we are using HD chips. The "film plane" of the CCD block is also much "thinner" than 35mm or 16mm - requiring more precise back focusing.

http://www.dpreview.com/learn/?/Glos...rration_01.htm

http://en.wikipedia.org/wiki/Chromatic_aberration

http://www.icexpo.com/HD100/old_aberration.html

The expensive and high quality 13x3.5 lens available for the HD100 supposedly will have much less CA.
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Old December 4th, 2005, 03:10 PM   #5
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Some time ago Nate Weaver has posted some clips, where You can see chromatic aberration very obviously:

- http://www.hdvinfo.net/media/nweaver/Downtown4.m2t (at the beginning of the clip look on the tower on the right side - it has a magenta fringe. When the camera has made its pan, You can see the same tower now on the left side, and the magenta fringe has changed to a little green one)

- http://www.hdvinfo.net/media/nweaver/Downtown7.m2t (for the last seconds of the clip You see a street with its upper part in magenta and its lower part in green)

I think, most of the people watching these clips would not recognize chromatic aberration. But once You have recognized it, You will see it all the time.


Quote:
Originally Posted by Daniel Patton
little to no noise, even in low light
I wished, it would be true. In my opinion the HD100 is very noisy in low light situations.
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Old December 4th, 2005, 05:02 PM   #6
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Thanks Tim and Robert.

Is this something that is typically fixed in post with color grading? Or do you know of a filter common to NLE applications that fix or reduce this?
Also, can the Chromatic Aberrations be avoided or reduced in any way during a shoot with lighting, etc.? Sorry for taking the thread off-topic.


As for low light noise... only if I gain up do I see a fair amount of additional noise, and that's to be expected. The JVC is about what I expected for an HD camera (in it's price range) in low light. I guess time will tell as I work with it more.
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Old December 4th, 2005, 05:26 PM   #7
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Daniel, do You find the following clips not noisy? They are from Tim Dashwood. Gain was not used.

- http://homepage.mac.com/timdashwood/...etup06-tk1.m2t
- http://homepage.mac.com/timdashwood/.../setup16-2.m2t
- http://homepage.mac.com/timdashwood/.../setup17-1.m2t
- http://homepage.mac.com/timdashwood/.../setup18-1.m2t
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Old December 4th, 2005, 06:21 PM   #8
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Quote:
Originally Posted by Robert Niemann
It is true that gain was not used. However, the gamma level was set at MAX, therefore introducing some noise. I was therefore able to get the same exposure as +6db to +9dB gain, but without typical gain noise. This noise has more of a film-like grain - equatable with "push processing."
Also, this noise is not visible in suitably lit scenes when pushing the sensitivity with gamma. These shots were done to test a "worst case scenario" using only available light from the street lamps.

Quote:
Originally Posted by Daniel Patton
Is this something that is typically fixed in post with color grading? Or do you know of a filter common to NLE applications that fix or reduce this?
Also, can the Chromatic Aberrations be avoided or reduced in any way during a shoot with lighting, etc.? Sorry for taking the thread off-topic.
There isn't really a filter that I know of to fix CA. Certain CC looks (B&W, Matrix look, Bleach bypass, etc.) would negate it.

It tends to get worse as you zoom the lens past 40mm. The lens also exhibits vignetting when zooming from 40mm to 88mm. The two seem to go hand-in-hand, so try to keep straight lines or objects of interest from the edges when zoomed in and you should be OK.
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Old December 5th, 2005, 12:26 AM   #9
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[QUOTE=Robert Niemann]Daniel, do You find the following clips not noisy? They are from Tim Dashwood. Gain was not used.

[QUOTE]

Yes, but with the shot being backlit and in what looks like total darkness (plus Tim's camera setting of gamma level set to MAX), it's still about what I expected. In all fairness, do you know of another HDV camera in the $5000 range that does better WITH the option of interchangeable lens? If so please tell me now before I buy the other matching camera.

I would like to see that same shot with the JVC's gamma not on MAX, just to compare noise levels in the blacks.
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Old December 5th, 2005, 04:14 AM   #10
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Quote:
Originally Posted by Daniel Patton
I would like to see that same shot with the JVC's gamma not on MAX, just to compare noise levels in the blacks.
Yes, that would be very interesting for me too.
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Old December 5th, 2005, 06:44 AM   #11
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I found the camera noisey, both in the sound itself made, and the images. I did get some really nice images though, but I also got some nasties.

http://www.nattress.com/JVC_Artifacts.jpg

Is the worst I got.

The biggest issue I found was it's lack of wysiwyg, in that the viewfinder is running at 60p while the camera shoots 30p, so you get fooled into thinking your motion is smooth, when it is not.

Graeme
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Old December 5th, 2005, 09:01 AM   #12
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Eeeeeee.... Graeme, that is horrid. I wonder how the other HDV cameras hold up under the same situation.


I'm not sure about the viewfinder but the flip-out screen does in fact show an obvious 60p to 30p change.
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Old December 5th, 2005, 09:09 AM   #13
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Viewfinder always looked like 60p to me when shooting 30p.....

Yes, that's horrid. All HDV cameras will do the same.

Graeme
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Old December 5th, 2005, 10:55 AM   #14
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Graeme,

Is the jpg. you posted from a pan, and does it look like this in the actual running footage (not just a frame grab)? Meaning; do the pans go soft and show bad exaggerated motion blurring?

Thanks.

I still wish you'd develop your "Film Effects" for the p.c. platform. Any chance?
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Old December 5th, 2005, 04:53 PM   #15
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That's what most of the frames of the pan looked like and it was plainly visible on both CRT and LCD monitors, so yes, that's what the running footage looked like. Most everything else I shot looked an awful lot better than that though, but even some controlled stuff wasn't as nice as I'd have liked, and all quite noisey.

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