Can anyone shed some light on some scanner queries? I am scanning 4x5" B&W negatives in the supplied holder.
My objective is to come up with a workflow to produce scans capable of 20x30" prints, and I would like, in the first instance, to provide my own scan - a drum scan by the service might be the final result if I'm happy with my own work.

1: The height adjustment on the holder appears to do absolutely squat to the final image quality. In fact, the documentation doesn't even talk about these little height adjusters at all. Correct?

2: I've been testing Epson Scan Vs Silverfast SE which comes with my Perfection V800
Epson Scan uses ICE as per hardware name. I think Silverfast uses the same hardware feature but calls it iSRD. It’s an additional infrared scan which maps dust and scratch marks then processing the original scan to remove the mapped marks. Correct?

3: (Observation) Epson Scan is faster than Silverfast - not sure why. The processing of iSRD in Silverfast takes forever.

4: Scanning at 3200 ppi on Epson Scan gives me black blobs/squares in lots of places where it appears to be below some kind of a threshold. 4800 delivers an acceptable image. Is this by design?
Silverfast 3200 does not give me the black blobs - not sure why Epson Scan has this threshold issue. Or is it a setting I need to discover?

5: The 4800 Silverfast scan creates a 1Gb TIF file for 4x5 area.
With Silverfast you can set Ilford HP5Plus 400 ISO - not sure what this would make the scan do - Epson Scan doesn’t offer such a selection. But Silverfast then defaults to CCR (Color Cast Removal) Why? for B&W?

6: Lightroom imports this file OK but you have to be patient during develop processes, but I am working with a printing service/lab and they are asking for an 8bit 254dpi file output which is only 95Mb in size. I'm seeing what it finally produces. The first guy I spoke to said he needed a 200Mb file but upon further reading of their spec, this is only created for 16bit. 8bit produces 95Mb. So I'm sending the 95Mb file to see what it produces.

7: I suppose I'd like to get scanner output which is close to the final output required. 1Gb files in Lightroom produce a real lag when you are doing spot removal and that sort of thing. If there’s no benefit in acquiring this file size in the first place, then there’s a good reason to avoid it. But my gut is telling me that you need all this information in the file to produce the final downsized output at its best. Is this a common observation?

8: When I export from Lightroom to Flickr, the largest size (Original) is 11414 x 14518 which implies 38x48" at 300dpi, but this is a JPG... Is this any different to TIF in terms of printability?

9: The service says it can print 20x30 from 5Mb JPGs - is this possible?
Here's the example I'm working with:
https://www.flickr.com/photos/metadi...7664271821431/

Obviously I'm just the same as all permanently confused people WRT resolutions for printing and screen output.
But some pointers from an expert here would be greatly appreciated.
In the first instance I'd like to see a 20x30 to see how my post processing is going. Even if I get a drum scan done, I probably want to post process myself a little.

Using the Silverfast help file is one thing, but every Youtube video I watch, the experts(?) always recommend not using any settings in the scanner software, instead recommending you use Photoshop etc for any adjustments.
It would be nice to read an authoritative masterclass on this subject.

regards
Alan