How do I achieve the film grain effect used in this image in Photoshop? I can never get it quite right.
The noise occurs as bigger islands than 1 pixel. To get it fill a layer with 50% grey and insert 100% noise.
Apply Gaussian Blur to the noise layer. This unfortunately may need some testing because blur isn't in Photoshop available as non-destructive effect like layer styles or adjustment layers (BTW Krita has readjustable blur). In my example the blur radius is 1px.
Insert 2 adjustment layers to get the islands with low enough contrast. Finally you must also reduce the noise layer opacity:
Adjustment layers are 1) Treshold which decide the ratio of black and white and 2) Curves which reduce contrast.
I adjusted the treshold to 50%. Both adjustment layers must have "the next image layer only" -switch ON.
Give to the blurred noise layer blending mode Hard Light and insert the image (=gradient) to the bottom. Reduce the opacity of the blurred noise layer small enough:
BTW. The grain can be in this version turned to apparent surface roughness. Merge the adjustment layers and the blurred noise layer. The apparent roughness is got by applying Filter > Stylize > Emboss:
That was zoomed in version of the image. The effect becomes milder with no zoom, so some experimenting is needed. Here's a non-zoomed screenshot. The opacity is increased to make the effect stronger:
- Create the gradient
- Convert the layer to Smart Object (In Windows, right click over the layer and Convert to Smart Object)
- Go to Filter > Noise > Add Noise and apply Monochromatic noise
Go to Filter > Filter Gallery > Texture > Grain and adjust available options according to your requirement
Note: Here is a related question and answers, which might help you explore more.