Alexa footage and 3D integration

[guiillt]

Hi everybody,
I will have to work with Alexa footages, full HD codex apple prores. Those footages are really bright and I wonder how to integrate 3D animations or 3D backgrounds from linear rendering of mental Ray xsi (dark one).
In digital fusion, we'll have a LUT , so we could see the final rendering, I could create 3D layers for 2D compositing, there won't be a problem but if I have to make 3D renderings, I 'll have to provide the whole shot (alexa footage with the 3D rendering inside) and I really don't know how to match the color of the 3D (Without the temp LUT). The final color will be in an other studio.
I don't know if I'm really clear and it'll be very helpful if you could suggest a way to process.

Thanks a lot

Guiillt

[pingking]

on the arri site you can use a LUT generator to build a LUT which can convert the alexa footage into linear space, then you should have no problem in compositing

http://www.arri.com/camera/digital_c...generator.html

[guiillt]

Thanks, but the main question I have is how to render the 3D part. For example I have a background extension to build, if I render the 3D part with a linear workflow or not, I composite my 3D render in Digital fusion with the Alexa footage and the right LUT activated, in this case the 3D part is too saturated and dark. I have to provide the final shoot without color correction (and without the LUT integrated) to another studio for the final color corrector .
Here is an example of Alexia footage :
http://2.bp.blogspot.com/-GjbQBpDaok...Day-A-LogC.jpg

This is an example of the footage I have to provide after integration of the 3D.

Maybe that's not a good way to process???, maybe I have to put the LUT in the output of Alexa footages and let the 3D rendering with few color corrections? And in this case I'll provide the shot with color correction (LUT), the other studio will only have few color correction.

thanks for your reply

Guiillt

[guiillt]

on the arri site you can use a LUT generator to build a LUT which can convert the alexa footage into linear space, then you should have no problem in compositing

http://www.arri.com/camera/digital_c...generator.html

Maybe I have to check your reply more, thanks for your time .
Guillaume

[guiillt]

I come back back again.
To sum up my question, when you integrate matte painting, or 3D objects rendered in XSI for example, do you work on color calibrated footages?
G

[pingking]

all footage you bring in your compositing software should be converted to linear colorspace. because all of the comp math is for linear images.

workflow would be:
loader of Alexa LogC -> convert to linear (via the lut from the arri site) -> compositing with your linear CG stuff -> convert back to LogC -> render
and use a viewing LUT to see your images better

[guiillt]

I understand, just don't know the way to" convert back to LogC"
thanks fir your time
Gui

[guiillt]

I found a node for fusion to revert
Thanks a lot
Guillaume

[pingking]

for saftey reasons: check if your footage is the same after you do a LogC->Linear->LogC conversion

[guiillt]

Yes, exactly the same !
Thanks
guillaume