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Early in the darktable manual (p13 of the pdf) there is the line:

"If you start your workflow from a raw image, you will need to have your final output sharpened."

Which confused me a little bit. Is one of the following interpretations correct or is there a better reasoning?

  • "In camera jpeg conversion includes a little sharpening so you'll want to replicate that"
  • "Humans like sharper images than the camera 'sees' so we all adapt by sharpening everything.
  • "There's something about RAW that implicity reduces the sharpness and you need to compensate"

(There is a similar question, but that focuses on a general sharpening of all digital files, and this interesting question is about the ordering of the steps)

  • 2
    As currently asked, this is probably a better question for the authors of the manual, don't you think? :) – junkyardsparkle Nov 28 '18 at 20:45
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All of your "interpretations" are technically incorrect because there is nothing in the statement or context (as you've described) to imply any of them. You shouldn't read more into the statement than what it actually says. That is not to say that there is no underlying reason for the statement, just that you cannot divine what that reason is.

That said, your proposed statements are often true, so most analog-to-digital image captures do benefit from some sharpening. Interpolation is inherently "blurry", which sharpening can counteract to some extent.

  • Yeah, I read it as a generalized acknowledgement that, while some sharpening is typically required post-demosaicing in order to get the results that many people will be looking for, darktable doesn't do this in a baked-in, invisible way... but does enable the sharpen module by default. – junkyardsparkle Nov 28 '18 at 20:43
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I looked into this a couple of years ago as I noted that at 1:1, images were not as sharp as they used to be.

The reason I came up with was that the image processing in Darktable when working with RAW images, and Exporting with the HQ option selected, the RAW images were kept at full resolution throughout the export option which made the process very slow for just a little more detail that was only noticeable at 1:1.

I recall having a conversation with a software developer about this and this was his explanation.

I believe that this has now been disabled as a default to speed up the process.

However, I no longer use Darktable, but it still seems the most logical explanation and thus the reason for the disclaimer.

If Darktable is using a downsampling algorithm to speed up the process, then the image will not be as sharp and require sharpening at the end of development which is what they are suggesting.

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