Thank you so much for your elaborate reply. It is truly appreciated. I again spent quite some time on this... I understand your thoughts about calibrating, but, no offense meant, I believe it is something else. When I get various colours when scanning the same thing and shown on the same monitor, using the same scanner, etc. I think it may be something else. Hence I went on to experiment with these TIF files. Flatbed scanned a colourful document, both as TIF and PNG. When displayed side-by-side I could not see the difference. Now, I made a few copies of the same (ctrl-c/ctrl-v), so 4 TIFs 4 PNGs and combined them into a PDF: they were fine (no colourshift). I expected that to happen as it happened when scanning multiple documents using the sheetfeeder. Nothing of the like. Now I discovered what likely is the problem and this is really weird... When performing a single scan, using the flatbed, I have two options: 1. show a preview first, then hit the [Scan] button, or 2. hit the [Scan] button instantly, i.e. without preview. There is the colour difference! I tried a few times, indeed, using the scan preview gets me much better results. Obviously this explains the colourshift when using the sheetfeeder (ADF - automatic document feeder): no preview. Last thing I expected...
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