Today’s Question: When scanning a black and white negative what advantage (if any) is there to scanning as an RGB image? I have been creating 48-bit scans as if I were scanning a regular color transparency, inverting the image to get a positive, and then trying to optimize the effects across the three channels (accounting for the film stock tint). I’m not sure I’m getting anything more than scanning as a black and white negative directly to a greyscale image.
Tim’s Quick Answer: The potential advantages of scanning a black and white negative as a color image are extremely minimal in terms of image quality in most cases. Except for scenarios where the black and white film has a clear color cast, I would tend to simply scan to grayscale, unless you intend to add color to the image later.
More Detail: There’s no question that scanning a negative in color mode yields more information than scanning in grayscale mode. However, that doesn’t necessarily translate into information that benefits the quality of your final image. With a truly neutral black and white negative, you would end up with three channels (red, green, and blue) if you scan in color, but the real difference between those channels would be minimal in terms of detail in the photo.
It is more important to scan at a high bit depth, and at the maximum optical resolution of your scanner, in terms of getting maximum information from the negative. Scanning in color will produce a file that is three times larger (because you would have three channels in the image instead of one), with very little difference in the final result.
If the film has a strong color cast to it, then scanning in color could be slightly beneficial. And if you intend to add color to the final image, it might make sense to start with a color (RGB) image, since that’s where you would be ending up anyway. But in general the benefit of scanning a black and white negative in color are minimal, in addition to the larger file size and additional workflow steps required for converting the color scan to a true black and white image.
So, I typically scan black and white negatives in grayscale mode, since the potential advantages of scanning in color are quite minimal.