waltervolpatto wrote: This diagram is about the order in the processing pipeline before/within/after nodes, not the operations a colorist performs. Offset comes after Lift/Gamma/Gain, so this tells you that you don't want to be adjusting luminance with Lift/Gamma/Gain after making a colour adjustment with offset in the same node, since doing so will change the balance and you will have to adjust offset again.
Yes but, I'm pretty sure that mathematically if you do LGG then offset, or offset then LGG the result will be the same.
If doing them in the same node with fixed values then you are right (at least, for lift/gain/offset; gamma may be different*).
But in the real world this assumes you will be adjusting offset literally at the same time as lift/gain. Take a solid colour clip (for illustration its easiest if it's a single colour rather than a tinted greyscale or proper image), and make an offset colour adjustment. In the same node, now adjust gain and/or lift luminance controls. Looking in the vectorscope, as you do this you will see that saturation isn't the only thing that changes, but hue does also. Therefore you will need to rebalance. On the other hand, if you adjust lift/gain first (can include both colour and luminance changes), and then adjust offset luminance, then neither saturation nor hue changes. If you are doing this with a proper image then the results may at first seem less obvious, but just compare the behaviour of adjusting lift/gain luminance in the same node as an offset colour adjustment with what happens if you do so in a subsequent node.
[*If you take an image, make adjustments to Lift/Gain and Offset (adding Gamma to the mix actually seems to lead to funky results) in the same node, then add 2 new versions which split the Lift/Gain and Offset into 2 nodes, one with Lift/Gain first and the other with Offset first, then the version that has an offset node before a lift/gain node will be different to the other two, which will be the same as each other. They will also be the same as a node structure that places Lift/Gain and Offset nodes in parallel. For some reason, if you add gamma operations then no node structure will match the result of the single-node operations, not even when done in parallel, and when ensuring no clipping takes place at any point. Note that this test needs to be done either with a tinted greyscale or a proper image, rather than a solid colour].