Scans not coming out sharp

[Digitizer]

Also consider losing pixels as shown here:

Do I need to change my lens/camera to scan medium format?

No matter how large your negative is, if your camera has a 4000 x 6000 pixels sensor, your output will be a 24 Megapixel image file. Scanning 120 film simply means that you’ll have to reduce the imaging ratio (move the camera away from the negative) to cover the wider format. Depending on what aspect ratio your negatives have, you can loose quite a few Megapixels in the process. If you cover the whole, uncropped negative area with one shot of a 24 Megapixel sensor camera… a 6x6 negative can …

Losing pixels means that you don’t get the full resolution and hence sharpness.