ID 155746 - Write Node - SLog2 colour space conversion slightly off in one direction only for native nuke color space handling (slog-2 s-log2)

Problem summary
Setting a Write node to write out in Slog2 colour space, when renders are read back in (and colour space is changed on the read to Slog2) there is a noticeable shift in colour between the original and the renders when they should be identical.

S-Log2 is scaled to expect 'IRE' range data, whereas S-Log1 and S-Log3 expect unscaled code values; this inconsistency is potentially confusing to users.

Customer reported version
Nuke9.0v4

Customer reported Platform
OSX 10.10 Yosemite

Steps to reproduce

1.  Create a ColorBars node
2.  Connect a Write node to the ColorBars
3.  Edit the colourspace in the Write node to 'SLog2'
4.  Render a single frame
5.  Read in the frame you just wrote
6.  Set the colorspace option on the new read node to 'SLog2'
7.  Compare the ColorBars node with the read node
Result:  There is an unexpected colour shift.
 

Workaround:
1) Open Project Settings (Edit > Project Settings).
2) Open the LUT tab.
3) Right click the LUT curve > Edit Expression
4) Select SLog2 from the list.
5) Right Click on the curve window > Edit > Edit Expression
6) Delete the current expression, and paste in the following which incorporates a legal to full scale, to bring it into line with Nuke's S-Log1 and S-Log3 curves:
((x*1023-64) / 876>=0.030001222851889303) ? 197.1*(10**(((x*1023-64)/876-0.646596)/0.432699)-0.037584)/155 : 0.9*((x*1023-64)/876-0.030001222851889303)/3.53881278538813
 
   NOTE: This workaround is believe to only affect the Read and Write nodes.

Reproduced by support

This bug has been reproduced in:

Nuke 12.2v2 - Windows 10

Windows 7 - Mac10.12 - CentOS6.9

Nuke11.0v2
Nuke11.0v1
Nuke10.5v6 
Nuke10.5v1
Nuke10.0v6
Nuke10.0v1
Nuke9.0v9
Nuke9.0v4
Nuke9.0v1

Earliest version tested
- This feature did not exist before this version

Expected behaviour
Both rendered images should be the same.

Actual behaviour
Both images are slightly different in color (Both GUI & with the Color picker).