It's funny how many decades we were striving to resolve the flaws in film photography and videography, only to get everything we wanted and then turn around and find a way back. Digital footage — particularly from the best cameras on the market, is characterized by incredibly clear, sharp, and clean footage. While that has always been the aspiration of the industry, now we miss some of the grain and character of shooting on film.
In fact, with all the latest and greatest digital cameras we have, flagship blockbusters are often shot on film. Take Oppenheimer for example, which was shot on a combination of IMAX 65mm and Panavision 65mm film stock. This is partially due to the enormous resolution that can be achieved with 65mm film stock, but also because the entire aesthetic has something appealing about it.
Although it is not a perfect replica, there are ways to create similar characteristics with digital files using LUTs. If you're interested in how it's best done, this video by Film Riot will explain.
One issue with adding film grain and other random imperfections to digital recordings, is that it greatly increases the bit rate needed to maintain fine details when there is motion. If you look at streaming platforms like netflix, amazon prime video and many others, if a movie uses film grain, you notice more compression artifacts, especially during motion, and for many free platforms like tubi, the heavy compression wreaks havoc on those movies while looking fine for ones that don't add much in the way of film grain.
I highly doubt fake film grain plays a big part in compression artifacts. Bitrates vary from service to service and content to content and possibly time of day. For instance, Netflix's content bitrate seem to range from 4 to 18 Mbps. Apple TV can go up to 40 Mbps. So, to blame film grain is pure conjecture since the only way to really know for sure is to have the same content (1 with grain, 1 w/o grain) on the same service provider streaming at the same bitrate during the same time.
I used to watch action movies from Netflix and Amazon on my 62" TV and never noticed compression artifacts during action sequences.
As for Tubi, they only stream max 720p at about 2.5 Mbps. I don't notice compression artifacts on my laptop 13.3" (2560 x 1600). It's more than fine. There's no wreaking of havoc.
From streaming there is no way to really do an AB comparison if dealing with a movie with added film grain, though it is something you can test with a basic camera and davinci resolve.
Record a well lit video so that the base ISO can be used, and pan the camera wide to side quickly, then export the video as h.264 5 Mbps (then add a node with film grain and then export again, then examine a still frame from the video in the middle of a pan.
You can also replicate it with a jpeg, Take any clean raw file (20MP or better) that you have captured before (base ISO and as little noise as possible). Export the image as a jpeg targeting a size of 5MB, then in photoshop add some film grain, then export the image again but adjust the compression to achieve a 5MB file again, then compare the resulting quality.
Beyond that, as good as compression has gotten, even with h.265 and AV1, they can't they can't detect noise and grain and treat them as details less worthy of preserving.
--- "though it is something you can test with a basic camera and davinci resolve."
--- "Record a well lit video…"
No need to test since I've been watching actual shows on an actual tv on an actual viewing distance. What you are proposing is to pixel peep and try (hard) to look for something. I don’t do that. I only do real world scenarios.
--- "You can also replicate it with a jpeg…"
In the last 12 months or so, I've been adding grain to most of my images. No less in quality. Granted, if one were to pixel peep, they'll clearly see the grain to which they may act like the sky is going to fall. :)
For the jpeg example, it would be more of a contrived test since you are adjusting compression to target a file size, though if just targeting a fixed quality or compression ratio, then the grain will not make a difference, and instead the jpeg image will just get larger, though if in a scenario where there is a very low file size limit, then the grain would negatively impact other details due to the more heavy handed compression needed to keep the file size low, if the amount of compression isn't increased,then when the grain is added, the file size will become larger.
Random example of leaving the jpeg quality set to 100, and simply adding grain to an image. The same behavior applies to video. Overall there is no issue with the use of grain for aesthetic purposes in a movie, though from a technical standpoint, if the if it is still targeting the same low bitrate, then quality have to be reduced via increased compression.
Though if not pixel peeping, many of the issues are not really distracting, and the only times they really stand out without much pixel peeping is if you are watching a video on tubi and you switch over to something like amazon prime video if they have the same video, and you notice that there are a lot of details that were lost in the heavy handed compression, though even then, it would be hard to sell how much more detail would be preserved if the original video had no film grain, though from a technical standpoint, we can assume some more detail.
For netflix and amazon prime video, you really need to pause during an action scene or fast camera pan, then examine the details, but if just watching at a normal distance and no pausing, then it is not very noticeable in terms of some of the artifacts of the compression that can appear around some details.
Waqas Qazi (DaVinci Resolve colourist) made a YouTube video on this topic. He goes into a fair bit more detail but ultimately concluded that the grain does make a difference and that the intended platform should be considered when publishing.