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8 bit effect in a 32 bit composition

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Sally James
8 bit effect in a 32 bit composition
on Jan 15, 2013 at 8:40:18 am

I'm converting a 60i feature film (1920x1080) to 24p and am in the process of de-interlacing (with magic bullet). Next step is Twixtor Pro in After Effects. With this second step, our clips are showing a flickering, strobing effect that looks poor without some blur added.

Twixtor's motion blur compensation creates strange (outrageous, actually) artifacting even in small amounts. Actors are being transformed into blotches of color with no definition from frame to frame so we need something else to blur the strobe effect we're getting. (ReelSmart Motion blur creates the same distortion problems--RevisionFX's algorithm may be why, but who knows.)

CC Force Motion Blur works great to fix the strobing/flickering. Very natural movement when applied. Problem is, it's an 8 bit effect and our After Effects compositions are 32 bit.

In this instance does it matter? Will it degrade the footage when we render? The footage is HD and is listed in the AE project window as 16 bit. Cineform is the codec, Film Scan 2.

I realize this must seem like a dumb question, but I've read that 8/16/32 bit only matters with stuff like color correction, gradients and other more elaborate FX. Does the 8 bit CC Force Motion Blur effect in After Effects harm my footage if I am doing NO color correction with these compositions? Each clip will be rendered out so we have our raw footage in 24p clips. All other FX will be addressed later. I don't want to reduce the quality for when the time comes to re-import the clips into new compositions for that FX work.

Again, I will only be adding Twixtor (32 bit effect) and CC Force Motion Blur (8 bit effect) to the 32 bit compositions. Then each clip will be rendered out at highest quality and archived.

Is HDR compander necessary for this type of work? If it is needed how should I add it?

Thanks for reading this and for any help you can give.

Best Wishes,
Sally


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Darby Edelen
Re: 8 bit effect in a 32 bit composition
on Jan 15, 2013 at 8:08:43 pm

[Sally James] "Again, I will only be adding Twixtor (32 bit effect) and CC Force Motion Blur (8 bit effect) to the 32 bit compositions. Then each clip will be rendered out at highest quality and archived.

Is HDR compander necessary for this type of work? If it is needed how should I add it?"


The HDR Compander may help you... or may not. It really depends on the footage. Essentially applying an 8bpc effect to your footage is going to force whatever colors are in that footage into 256 color values per channel (8 bits per channel). If you can use HDR Compander to get the most out of those 8bpc then that's great.

Generally speaking HDR Compander becomes most useful in situations where the footage either has superwhites or does not have evenly distributed color values (e.g. a dark underexposed shot).

The way I recommend using HDR Compander is to apply two instances of it, the first set to Compress Range and the second set to Expand Range. You can optionally link the Expand Range Gain and Gamma to the Compress Range's values as you'll always want these values to match.

Just after the Compress Range instance of HDR Compander I apply a Levels effect. This shows me the distribution of colors in the image after the range has been compressed. This allows me to make smarter decisions about how to bend the values with the first instance of HDR Compander. The goal should be to make the histogram as even as possible without clipping either the black or white points. Very often this will mean pushing both the Gain (to adjust white/black clipping) and the Gamma (to more evenly distribute the range of values among the available bits).

The last thing I'll mention is that CS6 includes the 32bpc version of CC Force Motion Blur, so now you have another reason to upgrade ;) Also Timewarp is 32bpc and has a decent "Motion Blur" option that may work for you.

Darby Edelen


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Sally James
Re: 8 bit effect in a 32 bit composition
on Jan 16, 2013 at 6:32:29 am

Problem solved. Upgrade, it is. Thank you so much for your fast reply, Darby. You're the best!


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