Hi, I am new to Photoshop and am trying to work out how to adjust a photo in Lab space that also has a CasMatch image (consists of nine sqaures of different colours including a white, a grey and a black square) by changing the Lab parameters for the black, grey and white squares in the image to certain Lab parameters (e.g. white = 93, 0, 0; black = etc)). The method has been used before (in scientific literature) using the color picker but the precise method is not spelled out. I assume I save the photo in Lab space first but then it is unclear to me, after selecting the squares, how change the Lab parameters of each, save them (I assume in different layers??) and then save the entire photo under the new Lab parameters of the black, grey and white squares combined. Any advice would be much appreciated. Or even just pointing me the relevant tutorial or help. It is probably quite simply done but I can't see my way forward. Thanks.
LinkedIn Learning have a number of excellent online Photoshop video tutorials, you need to look through them to see which might suit your purposes, such as "Photoshop: Creative Lab Color". (You can get 30-days free access).