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-   -   Video "Twitter?" (http://www.dvinfo.net/forum/jvc-gy-hd-series-camera-systems/123394-video-twitter.html)

Jon Springer June 9th, 2008 06:23 PM

Video "Twitter?"
 
I don't know if "Twitter" is the right word, but....

Everytime I shoot a brick building with my HD110u, the image just goes wacky with diagonal waving lines and scrolling interlace anomalies all over the place. It's just terrible. I know this happens with video cameras, but this is just seem way out of hand. Is this related to the design of the sensors, or could this be a setting problem?

I've adjusted the detail and that doesn't help. Has anyone experienced this?

Alex Humphrey June 9th, 2008 10:34 PM

1. are you looking at it on an HD set or down converted DVD? I've seen this a lot when shooting 30p, then converted to DVD. 24p hardly ever.

2. Now if it's HD you are looking at, take your detail down to minimum, and even try off. I shoot 90% of everything at Minimum. I can always sharpen in post if I want with a filter... too much edge enhancement is not worth trying to get rid of in my book. Now if your detail setting is minimum or OFF, and you are STILL having waving lines.. I have to ask... #3

3. Since this is summer.. could it be air turbulence coming off of the bricks or pavement in between you and the bricks? What focal length are you shooting? Longer the focal length, more turbulence, even in winter. If so, maybe try shooting the same shot first thing in the morning.

Liam Hall June 10th, 2008 01:17 AM

Quote:

Originally Posted by Alex Humphrey (Post 890682)
3

3. Since this is summer.. could it be air turbulence coming off of the bricks or pavement in between you and the bricks?

For real? Heat haze is one thing, but air turbulence at ground level - sounds nasty.

My guess, it's either a moire pattern or his mobile phone is too close to the camera.

Jon Springer June 10th, 2008 09:58 AM

Moire
 
Quote:

Originally Posted by Liam Hall (Post 890731)
My guess, it's either a moire pattern or his mobile phone is too close to the camera.

"Moire".....that's the word I was looking for!

It is definitely a moire effect with the brick pattern....but on the JVC it is more extreme than with any other video camera I've ever used. It shows up on the LCD viewfinder and upon regular SD monitoring of the Mini-DV tape. Detail is set a -4 (but I've tried other detail setting, to no effect).

Why is this abberation so extreme with this camera?

Jon Springer June 10th, 2008 10:03 AM

Quote:

Originally Posted by Alex Humphrey (Post 890682)
1. are you looking at it on an HD set or down converted DVD? I've seen this a lot when shooting 30p, then converted to DVD. 24p hardly ever. .

Here is exactly what I am seeing:

http://upload.wikimedia.org/wikipedi...icks_small.jpg

Kennedy Maxwell June 10th, 2008 10:21 AM

It is a moire. This can happen with many cameras when shooting such a finely detailed pattern . . . herringbone jackets, finely striped shirts & ties, etc. You could roll the lens slightly out of focus and eliminate it, but not enough to be noticed, or change the focal length of the shot (zoom in tighter to enlarge the pattern), or don't shoot a MLS of a brick wall.
Good luck,
Ken

Bill Ravens June 10th, 2008 10:36 AM

the way to mitigate moire/twitter, etc. is to add a little bit of blur to the footage.

Alex Humphrey June 10th, 2008 10:46 AM

turning the sharpness down to -9 or min or even off should fix it. I would stick with MIN instead of OFF however. The closer you get to OFF or Minium, the larger focal range you will have to play with. When I'm taping people in front of a chain link fence, at certain focal lengths in relation to distance of the fence, the fence shimmers during a zoom. (fence is 150 yards away, and zooming between 35-55mm cause shmmering, moire artifacts from the edge enchancement over sharpening repetitive patterns) My Sony DVCam's used to be far worse. Turning the sharpness down to MIN got rid of 99% of the shimmering. OFF got rid of the rest of it, but I felt the image went too soft with the stock 16x lens. Then I sometimes play with bumping up the sharpness with in my NLE and can adjust the sharpness (edge enhancements) with far more control through out the project later than I ever could in the camera.

Try Detail at OFF, Min, -9 and -8. I don't shoot anything above -7.

Marc Colemont June 10th, 2008 01:59 PM

I experienced the same thing when shooting sports and LED banners are present in the background. Shooting with SD camera I had this effect much quicker then now shooting in HD.
As I was curious why some footage had moire at some point. I did some tests in the stadium last winter while the LED banners were working.
Zooming the frame upto the level were the LED pixels come close to the resolution of the chip, the 'Moire' becomes very visible. It happens with any video camera or still camera. It's the nature of the pixels which are in row and coloms in a matrix. As one pixel corresponds with the edge of the brick pattern the next pixel shows the same edge or not which creates that effect of extra visible lines. It also happens when 2, 4 pixels correspond per brick/LED pixel, but less visible.
The only way to get rid of it, is zooming in or out to another level.
I have not tried to change the detail level during those tests. Next time I will try that.


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