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Question: Slides on v500

I am scanning a bunch of slides on the v500 and just not getting the results my lab can produce. My images are tack sharp and only just grainy... not much. But the scanner is producing color noisy unsharp images. I have tried pretty much every combination of settings and just can't seem to get the results I was hoping for. Any suggestions?? Am I doing something wrong or just expecting too much for an inexpensive scanner??