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Ugly moire in A720IS video

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Offline wap4

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Ugly moire in A720IS video
« on: 16 / April / 2008, 11:31:25 »
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  I am pretty disappointed at the video performance of A720IS. It shows ugly color moire patterns when I take videos
  of things that contain dense straight lines (e.g.-sleepers of rail lines).These are present even when I set video bitrate
  to 3x(via video parameters). Is there any way to reduce this or I've to bear with this?  
« Last Edit: 16 / April / 2008, 11:34:36 by wap4 »
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Offline intrnst

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Re: Ugly moire in A720IS video
« Reply #1 on: 16 / April / 2008, 14:57:35 »
Quote from: wap4 on 16 / April / 2008, 11:31:25

  I am pretty disappointed at the video performance of A720IS.
...

Did you try film in different light conditions? Good light makes good movies in my 710.
As we could expect, the opposite is true.

And as a general advice, use slow pans.
« Last Edit: 16 / April / 2008, 15:07:19 by intrnst »
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Offline wap4

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Re: Ugly moire in A720IS video
« Reply #2 on: 16 / April / 2008, 15:18:28 »

Quote from: intrnst on 16 / April / 2008, 14:57:35
Good light makes good movies in my 710.
As we could expect, the opposite is true.

 Yes,I shot videos of trains on sunny days and always noticed those irritating rainbow colored moires
 in the tracks. Videos which does not contain so densely contrasty area i.e. indoors are just fine.(I can bear
 the noise but this moire is unbearable) I am attaching sample screenshots to illustrate the fact. Have a look
 at the 2nd pic,tracks are full of orange-purple moire,though not very prominent and the radiator at the nose of
 the loco has got red,blue,green stripes along with yellow due to moire which obviously disappeared when the
 loco came close(the 1st pic)!. When the video plays,the moire also changes its pattern,making the situation more
 irritating. 
« Last Edit: 16 / April / 2008, 15:29:48 by wap4 »
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Offline Barney Fife

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Re: Ugly moire in A720IS video
« Reply #3 on: 16 / April / 2008, 18:01:56 »
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« Last Edit: 22 / April / 2008, 18:01:43 by Barney Fife »
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Offline wap4

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Re: Ugly moire in A720IS video
« Reply #4 on: 17 / April / 2008, 00:37:11 »
Quote from: Barney Fife on 16 / April / 2008, 18:01:56
If you can't bear it then I suggest you give up video as a hobby or as a profession.

 Sorry,can't agree with you as A720 produces a lot more moire in video than my friend's S3IS. Maybe its realtime demosaicing algorithm (fast) used for video capture is bad. BTW,The moire is not in the luminance channel,its purely on chroma channels.
« Last Edit: 17 / April / 2008, 01:05:48 by wap4 »
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Offline vit40

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Re: Ugly moire in A720IS video
« Reply #5 on: 17 / April / 2008, 03:58:29 »
It's normal for cameras with bayer sensors to produce moire on straight lines - you can see that even on TV, if taken with some older camera without 3CCD. Of course, some cameras are more prone to moire than other (different sensor and processing)
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Offline intrnst

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Re: Ugly moire in A720IS video
« Reply #6 on: 17 / April / 2008, 05:12:05 »
Quote from: wap4 on 17 / April / 2008, 00:37:11
Maybe its realtime demosaicing algorithm (fast) used for video capture is bad.
...

It makes sense, the faster the processor (A series vs S series) the better could be the compression artifacts. One question now: "Is it a hardware thing or it may be corrected/enhanced by fimware/CHDK changes?"

And wap4, please, keep your dissatisfaction up. If there aren't dissatisfied people, perhaps there isn't such thing as CHDK, at all.

___
btw: congrats for your work with ewavr on the variable video compression porting.
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Offline vit40

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Re: Ugly moire in A720IS video
« Reply #7 on: 17 / April / 2008, 05:28:37 »
You can't do anything, it's hardware thing (sensor and antialiasing filter) + demoire algorithm in processor. Has nothing to do with (jpeg) compression artifacts.

S3 is better than A720 because its sensor has more horizontal lines in video mode than sensor in A720. But S3 also produces moire on lines, at least mine
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Offline intrnst

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Re: Ugly moire in A720IS video
« Reply #8 on: 17 / April / 2008, 07:08:06 »
« Last Edit: 17 / April / 2008, 07:35:44 by intrnst »
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Offline vit40

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Re: Ugly moire in A720IS video
« Reply #9 on: 17 / April / 2008, 07:54:38 »
Moire can appear only on focused parts of the picture, where lines on the object (train etc) are aligned with pixels (horizontal or vertical) on the sensor. It's a kind of interference. Cameras with bayer sensors have antialiasing filter in front of sensor, to slightly blur the picture and reduce moire, and further reducing is done during processing in the Digic chip. Anyway, it's very hard to totally eliminate the moire

I don't like moire either, it looks very ugly, but on the other side, it's rarely a problem, unless you shooting mostly trains, fences and similar things with many horizontal or vertical lines
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