Scanner, what is it really doing?

[Hellblast]

Bought a Canon CanoScan 8600F to scan old 35mm slides and so far I love the pictures and the quality. I always liked the Canon Software so I went with that one.

It scans four slides at once in the plastic holder it comes with. The software does a good job at auto-cropping and scanning all four.

Question is this: It seems to make two passes over each slide for a total of eight slow-speed passes. This takes a lot of time, anybody know why two passes are necessary?

Thanks!

 

[corkyg]

A scanner's first pass is to determine the parameters of the object to be scanned. The second pass is the actual scan. You have 4 objects, and the software is treating each individually.

 

[Hellblast]

and a little while later I answered my own question.

Turns out the software's dust+scratch reduction does a double pass. Without that option, single pass.