Hi all,
Since H13 is with a 2.2 gamma, there is something strange when i convert a 16 bits image into 8 bits. I get banding and extra black area (see attached file).
If i save the image in 16 bits and convert it with gimp or photoshop, i get the a ‘normal’ conversion.

Thanks.

Are you using a Convert COP to downsample to 8b, or saving out the image to an 8b format? (such as JPG)

twod
Are you using a Convert COP to downsample to 8b, or saving out the image to an 8b format? (such as JPG)

I'm using a convert COP and after a ROP file output COP to save in PNG.

The attached image below is a simple screenshot with:
Left> File image node | Right> convert COP connected to File image node.

I'd suggest avoiding the Convert COP entirely, and just write to a png directly. It should do the conversion for you. Otherwise you're crushing the visible lower 25% of the image into 12 levels (out of 255), which is what is causing the banding ( 256 x 0.25^2.2 ~= 12).

twod
I'd suggest avoiding the Convert COP entirely, and just write to a png directly. It should do the conversion for you. Otherwise you're crushing the visible lower 25% of the image into 12 levels (out of 255), which is what is causing the banding ( 256 x 0.25^2.2 ~= 12).

Unfortunately, ROP COP doesn't have an option to setup the depth of PNG, and the result will be a 16 Bits PNG.

And in the same way, there is a similar thing with the File COP.

If you File COP a 8 bits image in a 16 bits project, you have this level compression. To get the good colors, i must uncheck ‘Linearize non-linear Images ’ BEFORE changing ‘File Raster Depth’ in Project Depth. Else, the Linearize option is disable in interface, impossible to change it. And connect a gamma with 0.4545, and all is fine.