[Openexr-user] compositing with EXR

[ant l]

Hello,

how do people generally work with EXR images in composting? More
specifically, I'd like to comp CG elements rendered as .exr over a cineon
plate.

thanks,
ant

[ant l]

Post by ant l

Post by ant l
Hello,
how do people generally work with EXR images in composting? More
specifically, I'd like to comp CG elements rendered as .exr over a

cineon

Post by ant l
plate.
thanks,
ant

Change your cineon to linear colorspace and then comp them together in
a compositor. EXR is just an image format. It's not magical or
anything. Maybe you could be more elaborate about what you don't
understand about exr?
--
Deke Kincaid
Momentum Lab
The Post Group
310-883-4313

Thanks for the reply..I'll try to explain better.
I understand that exr is just another file format and that it can be treated
as such. However what seems unclear to me is how this is used in a
production pipeline.
Typically, cineon are converted to linear format and stored in 16bit images.
OpenEXR images are read as 32bit floats (by Shake at least) and are quite
slow to work with. Is this a price that
we have to pay? I tried to convert them to 16bit (to match the cineon plate)
however, they get clipped to 1 which makes it a useless operation.

I guess my question is if people generally use them as 32bit floats or
convert them to something smaller? And if so, how?

thanks!

[John Coldrick]

Post by ant l
Thanks for the reply..I'll try to explain better.
I understand that exr is just another file format and that it can be
treated as such. However what seems unclear to me is how this is used in a
production pipeline.
Typically, cineon are converted to linear format and stored in 16bit images.
OpenEXR images are read as 32bit floats (by Shake at least) and are
quite slow to work with.

Actually I've had good speed response with OExr in Shake, I suppose it's all
relative. It's trivial to convert to 16, of course, if you want, but just as
you would typically want a depth map to be float, OExr gives you that much
more to fiddle with. It's options.

Houdini's compositor, for instance, keeps OExr images at 16 bit float
internally. AFAIK Shake comps at float internally. It's where it all ends
up eventually, which is why I'm a little curious why you're finding such a
noticeable speed hit. I find it *far* snappier on an NVidia FX3600 than 32
floats(probably due to using the clever nvidia half display hack which was
one of the great things about OExr - see the website). Graphics driver
issue, perhaps? I tend to render CG layers at 16 float in OEXR just for that
reason, since internally the renderer is already doing it at pure float and
dithering it down to whatever depth you want. OExr offers that great option
of depth yet excellent filesize performance.

Post by ant l
Is this a price that
we have to pay? I tried to convert them to 16bit (to match the cineon
plate) however, they get clipped to 1 which makes it a useless operation.

I'm not sure I'd call it useless, really. Getting values outside black and
white are very useful for some film shots, but even without that you're
getting higher depth within 0-1.

Post by ant l
I guess my question is if people generally use them as 32bit floats or
convert them to something smaller? And if so, how?

Personally, I'd only convert in the pipeline, e,g, using the Bytes node in
Shake. Sometimes I find what I want to do in a comp needs it from 0 to 1,
otherwise I need to manage it, so for a certain operation I'll nip it down.
Otherwise, I like the "room". :)

Cheers,

J.C.