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For best image clarity, 1080p or 720p HQ?

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Navarro Parker
For best image clarity, 1080p or 720p HQ?
on May 14, 2008 at 2:53:48 pm

Since both 1080p and 720p HQ record at 35Mb/s VBR, wouldn't 720p have less compression and fewer artifacts than shooting at 1080p?

I'm trying to chromakey some 1080p HQ footage and the noise levels are obnoxious. I have two cams set at 0 gain. Is there some other setting I should be using to reduce noise? The shot is a well lit studio setup.


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Craig Seeman
Re: For best image clarity, 1080p or 720p HQ?
on May 14, 2008 at 3:14:17 pm

Data per frame is also affected by frame rate 720p24 would have more data per frame than 720p60. Of course the motion vs the frame rate might impact the key too (motion blur for example at lower frame rate).

-3db can yield lower noise than 0db but it does depend on the shoot circumstances.

Since "well lit" isn't very technical it's hard to really determine if your key was lit properly. It takes a lot more than throwing lots of light on things to get a good key.

Since you're not describing what you mean by "noise" I can't help you there either. If it's properly lit with 0 or -3 gain you shouldn't get noise.

One might use color smoothing techniques if the issue revolves around 4:2:0 color space but that's "noise." I've seen keys pulled from the EX1 4:2:0 that look fine since the files are such high resolution (pixels close together help limit the edge nasties).

One might convert the source to Uncompressed or Apple Pro Res or some 4:2:2 format when doing critical compositing but again your description doesn't tell me enough to suggest what to do.

If you're in a "studio" situation one might consider taking the HD-SDI out of the camera and go to uncompressed or Apple Pro Res directly.

You really need to post frame grabs unless you can otherwise describe things in better and more accurate detail.



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Navarro Parker
Re: For best image clarity, 1080p or 720p HQ? (2MB image embedded)
on May 14, 2008 at 3:58:57 pm

I appreciate your quick reply.

I'm seeing a lot of noise on my source footage. Here's a 200% enlargement. Given that it's an animated GIF, the video noise is pretty close to what I'm actually seeing.

Photobucket

I did a eyedropper on the green portion and I'm getting a green R97 G194 B90 -- which seems like it has a lot of red and blue components to it. Is that acceptable?





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Craig Seeman
Re: For best image clarity, 1080p or 720p HQ? (2MB image embedded)
on May 14, 2008 at 4:08:43 pm

That sure is noisy. The real test is trying to do a key. I think a decent keyer would handle that. The thing I'd look for is to see how the noise impacts the edges (his arm for example).

I don't see that kind of noise in well lit shooting at 0 or -3db gain though so I'm not sure what caused the issue.



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Navarro Parker
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 14, 2008 at 9:42:15 pm

Just for reference, here is a portion of the set (shot at 1080/30p HQ at 100% magnification) after I apply Keylight or Primatte 4. (The green screen element is out of view) You can clearly see this lumpy granular noise. Any ideas? I tried shooting at 720/30p and the noise was the same.

I tried shooting at -3db gain and there was no improvement in noise over 0db. I'm previewing the video on an SDI HD screen and it looks completely smooth and beautiful. Is my noise problem caused from the XDCAM EX compression? I'm just really frustrated trying to get a noise free image.

Photobucket




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Craig Seeman
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 14, 2008 at 10:03:57 pm

How are you creating these animated GIFs?

Is it looking like this on an HD QC monitor coming from your edit system?

I just shot at +3db 720p30/60 (overcrank) of Tennis player on a poorly lit indoor clay court with ugly green walls and it doesn't look anything like what your GIFs show. I see some very fine noise in some parts of some shots but nothing like yours at all.



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Navarro Parker
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 14, 2008 at 11:41:42 pm

Yes. To clarify, the footage looks gorgeous when I'm previewing it *live* via SDI on a HD studio monitor. When I get the SxS card back to my FCP station and import the footage, this is what I get: chunky dog food.



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Craig Seeman
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 15, 2008 at 12:05:18 am

[Navarro Parker] "When I get the SxS card back to my FCP station and import the footage, this is what I get: chunky dog food."

But what are you looking at that footage with?

I send DVI to HDMI out to a 1080p HDTV, not ideal but it gives me an idea what'll look like on such a "typical" HDTV (not that there's a "typical" HDTV). I don't see serious noise in most situations until I hit +6db gain.

You certainly seem to have an "issue" but I seriously doubt it's the camera or the codec. You haven't mentioned how you're monitoring out of FCP nor have you mentioned what your attempt at keying looks like. You need proper monitoring to judge the material and then see if you have any issues keying.

GIF is not the right codec to look at things with subtle colors.
You really can't tell in FCP itself because it's scaling to play in the viewer/canvas.




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Rafael Amador
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 15, 2008 at 5:11:25 pm

[Craig Seeman] "GIF is not the right codec to look at things with subtle colors.
"

Really. Gif files have only 8b per pixel. Only 256 possible colors in a picture.



Mac OX 10.5.2-FC 6.02-QT 7.4.1
G5 2x2Gh 4GbRAM-BlackMagic Extreme
PMBP 17"Core2Duo 4GbRAM-AJA ioHD
JVC DTV-17"
SONY EX-1 . SONY PD170
..and always a big mess on top of the table.


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Craig Seeman
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 15, 2008 at 5:47:03 pm

[Rafael Amador] "Really. Gif files have only 8b per pixel. Only 256 possible colors in a picture."

It's the same reason people use JPEG, not GIF, for photos when building webpages.

In general, any additional compression by a lossy codec can amplify the noise. Of course one can smooth it to clean it up. In either case that absolutely NOT the way to analyze noise issue. One needs to look at the original files. One needs to examine on a monitor with high enough resolution to see that detail.

You can't even judge these things accurately in an NLE interface since it may be doing some fast scalling. That's why people use output to a monitor while editing.



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Navarro Parker
Re: For best image clarity, 1080p or 720p HQ? (1MB image embedded)
on May 15, 2008 at 7:45:30 pm

I'm previewing in FCP with a 30" Cinema display at 100% scale.

I think we're getting a little off track. The issue isn't noise in my animated GIF. I posted an animated GIF to illustrate the noise problem I'm seeing. It's the only format that supposts animation that I can embed into a forum. I realize that GIF only supports 256 colors. Not to sound snippy, but I've been in post and motion graphics for 15 years, so I have a pretty good idea of what's what. Which is why this noise issue is very concerning and puzzling.

The noise that you are seeing in the GIF is virtually identical to what I'm seeing in FCP and AE CS3 and Quicktime Player. It's in the movie. It's not a FCP scaling issue. I don't have a HD reference monitor available. So the 30" Cinema is it.


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