Filter Sharpen (UMS) / Why prescan doesn't function??

[quinta]

Dear Helper, I just installed a polaroid printscan 120, so I'm working via silverfast ai 6 and met a little problem.
If I put filter: sharpen( UMS ) in order to see on realtime to what extend I can sharpen the image, the dialog box opens, but I can't make a prescan, so nothing to compare. The left and right screen stay blank.
What do I do wrong, PDF file about this topic seems clear, but I can't get it right!
Thanks in advance
Quinta

[LSI_Belli]

Dear Quinta,

Make a prescan of your picture at first. Open the USM dialog box in the filter popup menu. Press the button "Prescan". Choose the zone you want to scan at full resolution by clicking on the prescan window (the big one). The mouse pointer is then represented by a square. The chosen area should appear in the USM dialog box. Adjust the parameters...

Regards,

Thomas