Today’s Question: How do you recommend removing film grain from scanned slides?
Tim’s Quick Answer: If possible, I recommend using the scanner software to reduce film grain. Otherwise, you can often get very good results by using noise reduction to reduce film grain.
More Detail: Film grain is similar in concept to digital noise, but it is different and so it can be a more challenging to minimize when processing an image scanned from an analog original. If the software you’re using for scanning supports a grain-reduction feature, that will often provide excellent results. If your scanner software includes a feature to reduce grain, it may be worthwhile to re-scan the images with that option enabled.
The other option is to use noise reduction software to help minimize film grain. The effectiveness of this approach will vary based on the specific grain structure. For images captured with relatively low-ISO film where the grain structure is relatively small and somewhat uniform, noise reduction is more likely to help. For very high ISO films with a more random grain structure, it can be more difficult to achieve a good result.
In particular, I’ve found that the Denoise feature of Topaz Photo AI (https://www.topazlabs.com/topaz-photo-ai/ref/273/) provides excellent results, especially with a combination of the Strength adjustment (for the overall noise reduction) along with the Original Detail adjustment, which helps maintain and enhance details from the original image.
The key with using noise reduction to reduce film grain is to carefully balance the settings to ensure you are reducing the appearance of film grain without significantly degrading detail in the image. Keep in mind, however, that you can also compensate for some loss of sharpness and detail from grain reduction by applying sharpening as well as adjustments such as Clarity and Texture found in Lightroom Classic and Camera Raw, for example.
