Heres the setup I used if anyone is trying to follow in a newer version of Blender. Found the Glare node worked a bit differently; the relative option is no longer available, and you don't have to do the texture work around mentioned. I was able to just use the straight up noise texture to create the film grain effect.
Hope it helps!
+------[Glare]-------+
+->o Image Image o--+-------------------------------------------------------------------------------------+
| | Glare o | |
| | Highlights o | |
| | Fog Glow / Medium | | | +--[Group Output]--+
| | Highlights | | | +->o Image |
| | Threshold 0.000 | | | | +------------------+
| | Smoothness 1.000 | | | |
| | [ ] Clamp | | | +-----[Overlay]-----+ |
| | Maximum 0.200 | | +---[Ellipse Mask]---+ | | Result o--++
| | Adjust | | | Mask o----+ | +-----[Overlay]-----+ | Color | |
| | Strength 0.675 | | | Add | | | | Result o---+ | Overlay | |
| | Saturation 1.000 | | o Mask 0.000 | | | | Color | | | [ ] Clamp Result | |
| | Tint [___] | | o Value 1.000 | | | | Overlay | | | [x] Clamp Factor | | +-----[Viewer]-----+
| | Glare | | | Position | | | | [ ] Clamp Result | | o Factor 1.000 | +-->o Image |
| | Size 0.592 | | | X 0.640 | | | | [x] Clamp Factor | +-->o A | +------------------+
| +--------------------+ | | Y 0.500 | | | o Factor 1.000 | +->o B |
| | | Size | | +-->o A | | +-------------------+
| | | X 0.733 | | +->o B | |
+--[Render Layers]--+ | | | Y 0.600 | | +------[Blur]-------+ | +-------------------+ |
| Scene | ViewLayer | | | | Rotation 0.186deg| | | Image o---+ | |
| Image o--+ | +--------------------+ +---->o Image | | | |
| Alpha o | +-->o Size | | +----[Multiply]-----+ | |
+-------------------+ | | | Fast Gaussian | | | Value o---+ |
| | | [ ] Extend Bounds | | | Multiply | +--[Noise Texture]---+ |
| +-[Relative To Pixel]--+ | | [x] Separable | | | [ ] Clamp | | Factor o |
| | Value o----+ +-------------------+ +->o Value | | Color o---+
| o Vector | o Value 0.900 | | 3D |
| | X | +-------------------+ | fBM |
| o Value | | [x] Normalize |
| | 0.617 | o Vector |
| | 0.617 | | Scale 400.000 |
+-->o Image | | Detail 10.000 |
+----------------------+ | Roughness 1.000 |
| Lacunarity 2.000 |
| Distortion 0.000 |
+--------------------+
Nice flow chart... did you know that under Window in the menu, you can save a Screenshot? ;)
Side note: as of 5.2 and newer there is actually a film grain node group. If you don't see the node group assets in the compositor, click view menu and check asset shelf. I don't remember which ones where available in 5.1. There was like 2 or 4. It may have the film grain one also.
The film grain group is new to 5.2.
It simulates analogue cameras like 70mm cinematic or super8. It's rather specific. For a more generic or digital camera simulation the sensor noise still makes sense to use and offers more control over luminance and chromatic noise individually.
Haha yup I did know that, but for new posts I couldn't post an image directly, so instead of linking to something that could expire, I did this instead :)