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Old March 2nd, 2004, 03:35 AM   #1
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Problem with gradient

Hi to all,

Well I think this fits best to the open dv discussion, so I post it here ....
Currently I'm making animated short sequence for the music video, and have a problem with PAL output. I made in photoshop dark blue gradient sky for the cartoon (720*576 resolution) , and when I make dv avi for PAL output, I can see the lines of colors on the video monitor. Everything looks fine on my computer monitor, but looks like some colors are missing on video output preview. First I thaught it is a compression issue, so I tried both Microsoft DV and Mainconcept, but the same : gradient looks bad .
Just to mention, I use firewire card (innoDV) with Canopus
ADVC100 converter.

Any help would be much appreciated,
Thanks in advance .
Darko
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Old March 2nd, 2004, 03:49 AM   #2
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First of all which NLE are you using and what version? I'm
suspecting Premiere, but still need a version number if that's the
case.

Second. What fileformat did you use to export from Photoshop
into your NLE and what settings did you use?

Lastly. You should set the pixel aspect ratio to the imported
picture on your timeline to 0.9 (DV NTSC) instead of the 1.0 it
is probably now. This should prevent your NLE from resizing
the image.

You also picked one of the hardest things to compress. A gradient,
most compressions have trouble with those in regards to not
messing colors or boundaries up.
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Old March 2nd, 2004, 04:06 AM   #3
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Thank you Rob for reply ,

I use Premiere pro for editing and previewing video output.
Compositing is done in After Effects, ie I made the gradient in Photoshop (format 720*576 RGB, saved as psd file), imported it in AE and rendered as avi. The settings in AE are : comp PAL D1/DV with aspect ratio DV (pixel aspect 1.067). Then when I import avi file into premiere (projects settings the same PAL DV), there is no need for re-render, it goes out right on video monitor, but looks incorrect.
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Old March 2nd, 2004, 04:25 AM   #4
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Why aren't you just loading the PSD in Premiere? What is the
pixel aspect of the FOOTAGE IN Premiere?
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Old March 2nd, 2004, 04:43 AM   #5
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Because the gradient is just background, I have several layers composited over (some bulidings, street, cars ...) in AE, and everything looks excellent except that gradient night sky hmh ....
The pixel aspect ratio of the footage in Premiere is 1.067, I think that is correct for PAL DV .
One more thing, I just tried this on friends Matrox Rt2000 NLE, seems correct to me .

Thanks again for help.
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Old March 2nd, 2004, 04:46 AM   #6
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Dark gradients in bands

You will find that dark gradients do display in bands of colour in 8 bit systems.

Photoshop dithers colours as it displays on screen - this prevents the bands appearing. DV does not include any such dithering, and the undithered colours get displayed by Premiere. Also your PAL monitor is a little less forgiving than your computer screen and shows these more clearly - all the more reason for checking everything on it!

My suggestion is to add some noise to the gradient before exporting it from Photoshop - that should fix the bands.

Julian
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Old March 2nd, 2004, 05:06 AM   #7
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What happens if you export uncompressed AVI from After Effects?
Make sure you are running AE in maximum quality mode (I believe
the default somewhere is not set for quality when exporting).
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Old March 2nd, 2004, 05:18 AM   #8
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Thanx Julian, I ll try with noise...

But it seems you're right about how gradient displays in 8 bit systems, that's very bad.

Best regards
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Old March 2nd, 2004, 06:10 AM   #9
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That is very good question Rob, I havent tried to export uncompressed avi from After Effects ... yes I've checked best quality under render settings .
As soon as I get home this afternoon I ll try to put uncompressed avi into Premiere , then let you know.
Thanx again.
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Old March 3rd, 2004, 02:18 AM   #10
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Huh, I tried to import uncompressed avi from AE into Premiere, and very strange thing happened - I couldnt export this avi to dv avi, because Premiere didn't recognize the video ie all frames were black. When I play this unc avi from media player, everything looks fine ....
Also I tried to import psd gradient directly in Premiere, but got the same bad video output.

Then I think I found the solution, Julian was right about this issue.
When I imported rendered dv avi back in AE composition, I could see those gradient lines on the computer monitor too . Seems it is the dv compression issue, now I think it can not be solved, tell me if I am wrong.

Thanks again for you effort
Best regards
Darko
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Old March 3rd, 2004, 03:03 AM   #11
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I hope that adding a little noise is a workable solution for you.

This 8 bit problem is why I always wish that video manufacturers would STOP HD development right now and switch their attention to low cost 10 bit development instead. I would much prefer a smaller screen of 10 bit gold, than a bigger screen of 8 bit rubbish any day...

Anyway, good luck with your animation,

Regards,

Julian
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Old March 3rd, 2004, 03:49 AM   #12
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Julian thanx for the tip,

I forgot to mention this in my previous post, tried also to add noise in Photoshop but didnt get satisfactory result on video out ( even small amount of noise was noticeable ).
If you want to share with me what type/amount of noise to add ,
that would be great .

Thanx again
Darko
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Old March 3rd, 2004, 04:18 AM   #13
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Photoshop settings

Darko,

I find that Add Noise filter, amount 1, Gaussian distribution (not mono) removes the banding satisfactorily with no obvious noisy pixels.

How is that for you?

Julian
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Old March 3rd, 2004, 04:38 AM   #14
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Thanx for the tip Julian,

Maybe I forgot last night to try with gaussian distribution, sorry.
I`ll try it this afternoon, I'm sure it would work.

Best regards.
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Old March 3rd, 2004, 04:30 PM   #15
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One note: if you want to use uncompressed you cannot use DV
AVI since DV is compressed. You have to select Microsoft AVI or
plain AVI and then use uncompressed as the codec (or select
none).

DV (AVI) and uncompressed are mutually exlcusive.
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