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Compositing with DPX files in after effects

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sim xiaozhang
Compositing with DPX files in after effects
on Oct 9, 2011 at 5:31:27 am

Hi everybody, I am currently doing a 3d composite onto a dpx footage.

Was wondering whats the correct way of going about dealing with dpx files in after effects.

The dpx footage looks a bit washout when i imported it. After doing some research online, mostly from Pete O'Connell's working with cineons article at creative cow.

I setup my after effect project to 32bit comp with "none" working space. Then i applied a cineon converter effect (log to linear) to the footage. Change the highlight rolloff to 0. The white in the footage is looking good but the whole image looks dark and contrasty now. So i push the gamma to the maximum 5 value and got a decent nice looking image.

Then I composite my 3d renders layers over the footage, matching the levels and colors to this "corrected" footage.



Is this the correct way of working with dxp files? Am I messing up the raw dpx footage? (As i am just tweaking the cineon converter effect values, pushing gamma to max, to make the footage to look like what i think it should look like.)

Should i just match my cg renders to this self-corrected looking dpx footage when compositing? I am using after effects CS3.

Thanks.


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Tero Ahlfors
Re: Compositing with DPX files in after effects
on Oct 9, 2011 at 9:39:18 am

Is it possible to get a LUT for the footage? It's easier to use a LUT instead of just eyeing it.


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ben g unguren
Re: Compositing with DPX files in after effects
on Oct 9, 2011 at 2:09:54 pm

You need to apply the cineon converter TWICE. Once to move your footage to linear space, and once to bring it into logarithmic space. Here's one way to do it, using adjustment layers:



1. (Top Layer) Adjustment layer: Cineon Converter effect: Linear to Log
2. 3D composite layer
3. 3D composite layer
4. 3D composite layer (etc, etc)
5. Original footage: Cineon Converter effect: Log to Linear


With this kind of setup, your 3D composite layers are doing their work in linear space, which can give a nicer composite if you have 10-bit or higher source footage (which I"m assuming you do, as you are using DPX footage). Keep in mind, however, that the difference is often quite subtle from what you'd get if you were working the entire time in log space.

If your DPX is looking a bit washed out, place an adjustment layer over the cineon converter layer and apply the levels effect. Clamp the white and black levels a bit to make it a bit more contrasty.

Ben Unguren
Motion Graphics & Editing
http://www.mostlydocumentary.com


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sim xiaozhang
Re: Compositing with DPX files in after effects
on Oct 10, 2011 at 2:47:42 am

thanks guys for ur replies.

Tero, i will try asking the post house for the LUT.

Ben, just wanna confirm. I apply a cineon converter to the original dpx footage and tweak the values to make the images to what i think it should look like. Then composite my 3d renders on top to match this corrected footage. Finally add an adjustment layer of cineon converter with the same tweaked values but is "linear to log" to bring the whole thing back to the initial washed out look for exporting out.

So i am not messing out the dpx footage? Am i correct?


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ben g unguren
Re: Compositing with DPX files in after effects
on Oct 10, 2011 at 2:57:56 am

[sim xiaozhang] "So i am not messing out the dpx footage? Am i correct?"

I do the entire setup, with both cineon filters, before doing any compositing. That way I'm always looking at the final image. (Linear space doesn't make a lot of visual sense to me, though I can understand how the math works, more or less.)

If you didn't have any composite, but just the base DPX sequence with cineon log->linear, and then the adjustment layer linear->log above that, the image should look exactly the same as the original DPX.

As for the slightly washed-out look (not the linear-space super-washed out look), I've seen DPX files do this before. I'm not sure if it's a color space issue or not. I received color-corrected files from the colorist, and after I added effects to the DPX files, I rendered back out as DPX. These went back to the colorist, who looked at them and tightened the levels to clamp the blacks and whites a bit. I'm guessing it had something to do with how I was interpreting the footage, but I never figured that out. The colorist told me that next time I could just clamp the levels myself to bring the blacks closer to 0 and the whites closer to 100.

Ben Unguren
Motion Graphics & Editing
http://www.mostlydocumentary.com


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sim xiaozhang
Re: Compositing with DPX files in after effects
on Oct 11, 2011 at 11:23:08 am

Thanks Ben.

Still waiting for the post house to reply me. But thanks for all ur help.


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