Hi, I'm rather new to Affinity Photoshop- I'm not amazingly experienced in Adobe Photoshop, but I'm way more familiar with that....   I recently began shooting color negative film and dislike the color correction in my scanners software and the Vuescan software and wanted to learn how to do it myself in photoshop. I found a tutorial online, however, I cannot figure out how to do the "Levels Clipping Mask," ...here is the tutorial: https://petapixel.com/2017/02/01/edit-color-film-negatives-photoshop/   Basically, I know from the Affinity help page that I can press the "alt" key when I'm adjusting the Black and White levels when I'm in specific colors such as red or blue, but it just turns my image either all black or all white, and I'm not sure how to make it actually work like it's supposed to? It seems to do the job when I do it on the Master for the RGB levels, but not any specific color? Am I doing something wrong?    I hope this makes sense! Thanks!   -Jenny