I've been working very hard recently on emulating the film look for digital cameras and have settled on a grain method that's very close. First let's take a look at some film grain, shot at one stop intervals, scanned at 24MP and presented here at 100% magnification. Top row is the "digital" version, the average RGB values of the extracted film scans in the row below:
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I think that most methods of simulating film grain involve taking a grain scan that's been normalised to an average of 128 RGB and then applying an Overlay blend mode. When we do that we get this, and it's very apparent that them middle grey patch is bang on but the amount of grain in the shadows and highlights is not:
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Now, here's my method using a grain scan and a PS action. The amount of grain in the shadows and highlights of the digital row (top) is much closer to the film scan (bottom):
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Here's how I do it in sRGB colour space in Photoshop:
Acquire a scan of film grain and make sure that it averages out at 128, 128, 128 RGB
Convert this and digital file to sRGB
Place grain layer over the digital file and resize if necessary
Change blending mode to Soft Light
Duplicate grain layer twice so now there are three Soft Light grain layers (the first two of these will take care of midtones and highlights)
Select the last grain layer which will deal with shadows and apply the following effects (not adjustment layers, we only want to alter this third grain layer)
Add HSL effect: Saturation +50
Add Color Balance effect: Yellow midtones -30
This gives use a highly saturated, and slightly warmed grain layer for the shadows
Then double click to bring up Layer Style menu
We're looking for Blend If
Leave "This Layer" at its default but set "Underlying Layer" to 0 0/85. So you're bringing the white slider down to 85, then Alt click to split that slider and bring the left portion all the way down to 0
Depending on the sharpness and resolution of the grain scan and the resolution of the digital image you might want to slightly blur the digital file. None of the fine details in the digital should be smaller/sharper than the actual grain.
That's it, all done! If you record the above as an action (use File>Place Embedded to import grain file) then you can batch apply this to folder of images. Duplicate it and double click the Place command in the action when you want to use different grain.
Let's have a look at a real world example.
Digital file with Portra 160 film emulation:
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The same file with Portra 160 grain added as per the instructions above:
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Kodak Portra 160 film scan:
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