Well, sorry to go on so long about this, but I keep adjusting my work flow to fit the changing requirements of the images, and I thought I would keep you informed. If you are coming to this fresh, you might have a look at post 1, post 2 and post 3 first.
The earlier slide sets I had been scanning had a lot of water horizon shots, and because tilted water horizons bug me (unless trying for that effect), I felt the need to rotate the scanned images to level, and so I set the “Border (%)” parameter of Vuescan to 5% to give me essentially an extra bit of space for cropping around the fairly good auto crop selection, since I was rotating and cropping manually afterward. The rotations were often minor, and due to slight slide mismount or angled position in the batch slide holder as, or more often than, photographer composition errors.
However with the more recent sets (photo here a typical example from one) I feel no urgent need to rotate. Indeed, I’d be hard pressed to figure out which way to rotate and how much, without a level horizon to guide me. So I began setting the “Border (%)” setting to -1%, in order to crop off the slight black borders that were being included in the automatically selected crop (it’s fairly conservative about your borders). This yields sets in which I don’t have to manually post process every picture afterward, but only the occasional one. Again, just to be clear, this is in the second pass from scanned RAWs to baked TIFFs. I’m still including the 5% extra border in the initial scans to RAW, just to be safe. And having the RAWs on disk means I can rescan the entire set to TIFF without loading a slide, in a fraction of the time. Sweetness.
Again, using the load/save settings feature of Vuescan made it easy to save these settings under the name “raw-scans-to-cropped-tiffs”.