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alexx
03-13-2008, 05:18 PM
hi,

i am currently working on a commercial.
the footage was shot on film, but now as i try to key it i run into severe trouble.

to mention: i am quite new to film material. most of my recent work was shot on video formats.

the film footage we got is extremely noisy. the problem: it is COLOR noise and not luminance noise. so when i try to key that footage i get small sized holes all over the foreground.
with some helper mattes and median filters i was able to key at least more static shots.
but now i have one that involves a lot motion blur and i am really stuck.

#1 is it normal that film material has that much color noise?
#2 is there a way to key that?

any help appreciated.

here for you to see: a "sample" from a near white are of the image (cant show complete image) - guess why my key does not work

cheers

alex

http://img182.imageshack.us/img182/4853/filmwhitefv7.jpg

here a part of the image with motion blur. this is the result with initial key done with keylight

http://img177.imageshack.us/img177/6130/initialkeyis0.jpg

WmH
03-14-2008, 03:25 PM
Normally film shot in that kind of light is tight grained, but film type, speed and processing are normally up to the DP and some understand the downstrem implications better than others. :rolleyes:

High motion blur shots are well suited for inter-frame blending which will damp (normalize) the color noise.
This is (best) done in the timing tab of the input node.
Rather than spew directions here is a screen shot of a recent project (ignore the pulldown it was telecine'd media, start with retime mode) This will give you 3 frames (backward and forward) of blend (with decreasing intensity with frame distance)

http://idisk.mac.com/holderness/Public/Concept/Frame_Blend.png

alexx
03-14-2008, 03:36 PM
yeah.. i seem to have met "one of the others" :)

thx for that tip. btw: working on shake 2.46 here, so i guess that frame blending is the same as the average node here for me on my shake.

unfortunately that scene contains both: static elements and very fast elements: its some people clapping their hands.

they clap so fast that the blending really messes up the image. i would rather think that technique would be useful for calm shots than fast ones.

but thanks for the idea anyway.

i had some success now by blurring the color values of the footage. (converted to YUV colorspace, blurred U and V and revert to RGB). that kills a lot of the color grain. (of course messes up the colors a bit as well.) but at least i got a key that works a bit.

cheers & thanks so far

alex

WmH
03-14-2008, 04:18 PM
If you can't use interframe smoothing then I think you are doing the best you can. (with the chroma blur)
I often look through the channels in several colorspaces (cmy,his, ect) to see if I can spot one that seems to isolate (concentrate) the noise and blur that channel (and then flip it back to rgb.)

Sorry I can be more help, but I have been there, sometimes all you can do is niggle it from 5 directions and finally get an "ok" key.

alexx
03-14-2008, 04:29 PM
im on the track :)

thanx

alex

beaker
03-16-2008, 12:17 AM
i am currently working on a commercial.
the footage was shot on film, but now as i try to key it i run into severe trouble.Couple questions, how did you get the material? Dpx, cineon, or some type of tape. If it was tape, what kind?

#1 is it normal that film material has that much color noise?Yes, that is pretty normal for most film.

beaker
03-16-2008, 12:23 AM
thx for that tip. btw: working on shake 2.46 here, so i guess that frame blending is the same as the average node here for me on my shake.The convert tab in shake wasn't added till 4.0.

i had some success now by blurring the color values of the footage. (converted to YUV colorspace, blurred U and V and revert to RGB). that kills a lot of the color grain. (of course messes up the colors a bit as well.) but at least i got a key that works a bit.Don't combine the footage in the keyer, just use it to create a matte. Before Shake 4.0, the keyers only work in 8 bit(primatte) and 10 bit(keylight), so all your footage will be clamped. Just switchmatte the alpha out of the keyer onto the footage. If you have any type of denoise or degaining plugin for any app(AE, etc...), I would run it through that and bring it back into Shake in order to create a matte.

Steve Wright's compositing book has a bunch of tips on this type of stuff too and he uses Shake to create the examples.

Isn't is about time you guys move beyond Shake 2.46? :) :) :) No offense but I've heard you bitching about it on the forums for like 2-3 years and that version of the software is atleast 7 years old. hehe

alexx
03-17-2008, 09:42 AM
Isn't is about time you guys move beyond Shake 2.46? :) :) :) No offense but I've heard you bitching about it on the forums for like 2-3 years and that version of the software is atleast 7 years old. hehe


hehe sure :) but unfortunately not my decission. but to be honest: that old version works for most we do. we currently indeed plan to switch this year to nuke.

we got the footage from a telecine in 16Bit tiff files. for a test we also got dpx files. there was no difference to us in quality.

just on friday we got footage from another job which was done on film as well and there we got way better footage. the noise is mostly a luminance noise and not a chroma noise like in the first footage, which makes the keying far easier.

i did not know about the bit-depth limitation of the keyers in our version, but since we already only used the masks as a switch matte on the original footage as you said, we are safe.

i tried tinder tools to degrain the material as well, but for the first footage it did not help enough. that noise is really beyond what should be right.

thanks for the tipps and help

alexx

and p.s.: i am not really bitching about it :) only a slight bit sometimes

beaker
03-17-2008, 10:03 AM
we got the footage from a telecine in 16Bit tiff files. for a test we also got dpx files. there was no difference to us in quality. Ok cool. The reason I ask is because I still see projects where they get it telecine to HDCAM which is 8 bit 3:1:1. So not only do you have the film grain to deal with but then add the horrible HDCAM compression on top of it.

alexx
03-17-2008, 10:08 AM
*grin* i had that once - horrible :)

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