I think it’s just another tool in your editing toolbox. Can help get a less clinical look (you’re basically adding imperfections), but as any tool, should probably be used in moderation.
I tend to add a little bit of grain. I'll add up to like grain level 30 in LR, but usually no more. It depends on the photo though, sometimes I want the clean look.
It’s also a « trend » in videography and cinema. People are tired of the overly digital and perfect look, and grain or diffusion is a nice way to tone it down. I use it directly in my film simulations, trying to find a nice middle ground.
I'll use it mainly on gut feeling, but most of the time I like it if the image is more ethereal. I've attached some examples of mine where i have this feeling and I like the use. I think a lot is to do with the lighting that affects my choice.
Love love LOVE grain, often I find boring photos I take will instantly 'vibe' up with a bit of crunchiness. There are definitely more pleasing ways to add grain, I find LR to be a little unappealing at times so will go more towards Dehancers grain, or Caleb Salvadoris grain which uses masks to add grain in a more filmic way.
I remember once being present during a conversation between Kosenko and Pinkhassov, where they were discussing how clean, pure colours in absence of texture or overall tone, produce a sense of disconnection between elements — and Kosenko said: More “mud” — more bond (unfortunately translation loses the rhyme). In my opinion, adding grain to a digital image can be such bonding mud.
I'm not affiliated with this product at all, I just saw it yesterday – it's called The Grain thegrain.io. It looks like a final step to the editing process, with some features that look interesting (focus control of grain so it doesn't kill detail and sharpness, and print simulation).
Not really looking to add to my workflow, but it does look interesting.
Unless I zoom in a lot, it’s hard for me to notice the difference after adding grain. Impact 30, Granularity 50 in Capture One - am I using it too lightly? I also can’t see the difference between the types of grain haha.
Do what works for you. There's plenty of examples of really great photography that uses heavy grain - Trent Parke, Moriyama, Bill Brandt. Equally, there’s many examples of work that doesn't.
I do think it's important not to generalise and to judge work on content rather than process, of which there's rather too much online.