Ansel primaries usage

[dopszli]

Hi all, I have been testing Ansel for some days and I may have some very basic questions:

1. the primaries in the color calibration Mixer tab does not seem to work the same as in eg. Darktable, Lightroom. For example moving the red slider 20 degrees tints the image (even the neutral parts that are protected in other apps). Is this the intended way it works or am I experiencing a bug?
2. The Photographic grain module is very nice, but its output depends on the output resolution. I often export images in 1920 width and the grain size grows when exporting in smaller resolution than the original. Is it the intended way it works? If so, can I visualize the to be exported result in the darkroom window?

Exported at resolution 5996 px then downsized to 1920 px Exported at 1920 px

[aurelienpierre]

the primaries in the color calibration Mixer tab does not seem to work the same as in eg. Darktable, Lightroom. For example moving the red slider 20 degrees tints the image (even the neutral parts that are protected in other apps). Is this the intended way it works or am I experiencing a bug?

Color calibration is a channel mixer. The primaries view of that channel mixer is a different representation of the channel mixer control. RGB works under a premise of additive light, meaning white = R + G + B in equal parts, so it's only natural that changing one of these quantities results in tinting the image. Not sure what you are comparing this view with from other software, but primaries of the RGB colorspace should behave like that.

Ansel has another color primaries module that doesn't manipulate primaries of the colorspace but human-meaningful color primaries. This one nails neutral colors at their original place and is the actual equivalent of the Lightroom HSV mixer. Not an RGB channel mixer.

The Photographic grain module is very nice, but its output depends on the output resolution. I often export images in 1920 width and the grain size grows when exporting in smaller resolution than the original. Is it the intended way it works? If so, can I visualize the to be exported result in the darkroom window?

The pipeline goes final resampling -> filmic -> photographic grain. Grain should happen after the curve. The curve should happen after the resampling. Grain synthesis can't work on subpixels. If that bothers you, feel free to move final resampling after photographic grain, but resampling on non-linear RGB may trigger chromatic aberrations at edges.

[aurelienpierre]

In photographic grain module, the grain synthesis model has been changed to allow sub-pixel geometry, which behaves better when downsampled: d147c86

In color calibration module, I added a new mode called "white-preserving" that seems close to what you ask and is conceptually closer to what Darktable does in its (poorly-named) primaries module: d147c86 See the doc for more details.

[dopszli]

Wow, both of them seems to work perfectly! Thanks! Much easier for me to manipulate primaries this way.