Hey funk,
thx for your reply.
Your hint with the Imager settings in Modo led my to the right place and I found the culprit!
In the Imager settings of Octane in Modo there are two different sRGB settings: "None (sRGB)" and "ACES: sRGB" – those are NOT the same!
I had the former, but need the latter.
Once the view transform in Modo is set correctly to the same I have in Nuke (both "ACES sRGB") all is good!!!
Now this workflow works as expected:
- Display the image in Modo with a specific view transform (Imager settings OCIO View) - e.g. "ACES sRGB" (if that is the appropriate for your monitor)
- Save the image in any file format in any color space
(can be PNG with "Output - sRGB" or an EXR with "ACEScg", or...) - Load the image into Nuke and set as the input transform in the reader node that very same color space
(that way the data get's "decoded" and transformed into Nukes internal color space) - Make sure your viewer transform in Nuke is set to the same as the Imager OCIO View setting in Modo/Octane
Then everything is peachy
As to the choice of image format and color space:
The choice of image format and/or color space has influence on the quality of the image transfer (which colors can be transferred at all and in what quantisation/bit-depth) - but the overall look of the image should stay the same. There can be banding etc. (if the quantisation of the specific colors that are used is insufficient) and there can be issues if extreme color values cannot be represented by the data type of the format (e.g. values > 1 or < 0 in an integer format) - but apart from that in my view there is no
wrong format or color space.
That being said, I absolutely prefer floating point formats (like EXR)! There were also external reasons to use PNG (an integer format) in this particular case...
(let alone that EXRs also offer layers, overscan, etc.)
@funk - as to your Fusion setup:
When reading in the image with the OCIO node and transforming it to sRGB that means that you then also have sRGB as your
working color space - meaning that Fusion will apply all it's operations on data in that color space, which I think is not ideal. If you do that, you of course need a neutral viewer transform on an sRGB monitor - the data
already is sRGB...
I personally prefer to transform the data into a linear working color space (a
must in Nuke!) and apply an appropriate viewer transform, just to
see the image correctly. That way all the nodes operate on linear data, which I think also in Fusion is as intended and makes dialling in values feel more natural - and also most nodes operate better on such data (keyers, filters, glows, ...). And in the end of course apply an appropriate transform when writing the data out.
All in all: It works not as expected for me and many thanks to everyone for your time and help!!
Cheers!
Johannes
PS: To finally confuse everyone totally: The fact it worked with the PNGs even with the wrong Imager setting is just because for the PNGs I also chose the wrong output transfer ("sRGB" instead of "ACES sRGB") - which compensated for the wrong view transform...
funk wrote:I need to add a note here about saving PNGs with Octane. I only noticed this while testing the 2 different ways you can use ACES in Octane.
If you are using an ACES OCIO config with imager > OCIO view = "ACES: sRGB", you need to select color space = "Output - sRGB" when saving to PNG.
Selecting color space = "sRGB" will produce the wrong result.
If you are using the imager > ACES Tone mapping checkbox instead, both color space = "sRGB" or "Output - sRGB" will work for PNG saving. (NOTE: they only show up if you have a config loaded)
This seems to be some sort of quirk...
I don't recommend using PNGs, but its good to be aware of this so your comparisons between the EXR and PNG are correct.