I spent yesteday scanning a load of Tri X and Delta 3200 negs and they provide no blacks. This is confirmed by the histogram which is short - black starting between 15 and 20 and fading well before 255. I've attached a typical example.

I suspect that the scanner needs setting up differently - it's an Epson 4900 (flatbed) at the university. Can anyone make any suggestions?

Thanks
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You just need to go in and adjust levels.

With a Histogram like that your scanner is probably doing a very good job capturing the dark areas of the film you're scanning. That's a good histogram for a scan IMO.

I've been adjusting levels all day. I'm not too happy with the results though, the pics lack shadow detail

One thing you might try is making a really nice print from the negs and then scanning that.. I've had good success doing that with tricky B&W stuff. Kinda need a darkroom though..

The trick is to move your black-end histogram slider towards the curve, while watching the image, until you have rendered unimportant shadow details as black (Zone 0 for us film luddites), but left desired detail in other dark areas, which by definition are not jet black (more like Zone II or III). This can be tricky, and is essentially an aesthetic decision.

That said, it may be that you need to increase your film exposure to capture more shadow detail in the first place. It may also be a limitation of your scanner, but I agree that the histogram looks as if you're getting all the black there is to get from that negative.

I'm not sure what the source of the "unhappiness" is. Is it having to manually adjust each shot (run (auto)levels or an adjustment curve in batch?), or the lack of detail (or both)? The detail is what it is and I don't think any scanner adjustment is going to help (assuming no gross mistakes in setting resolution etc).

Maybe you're asking how to have the scan exposed "to the left"? That's going to give you even less latitude in getting detail out of the shadows (see MR's article on Exposing to the Right for more explanation). http://luminous-landscape.com/tutorials/expose-right.shtml