I have detected dark stripes in some of my scans. Very likely the stripes are always present but only visible under certain circumstances. My scanner is a Microtek ScanMaker 5 used at 1000 samples per inch on 4x5 Velvia among other films. With this scanner the CCD's step across the short side of the film, (that is, the array is across the long side) and the stripes are parallel to the long side about every 120 pixels and are roughly five pixels wide. The stripes only show in the sky and where the sky very cloudy but bright. The scanner reports the numbers as 249, 255, 251 for R, G, and B respectively on a chrome I was working on today. Visually, this sort of chrome shows a totally dead white sky; PhotoShop can find some texture but it also finds these stripes. The only thing I can think of is that the stepping motor is stalling slightly every 120 pixels (or every 0.12 inches) and burning those pixels a bit darker. So far, Microtek has been no help. Does anyone have any ideas?

-- John Hennessy (northbay@directcon.net), January 03, 2002

Answers

maybe you should change the software, some of them are using multi pass, to reduce that kind of problem.

-- dg (sacripant@online.fr), January 03, 2002.

Hi John,

Maybe you should try to change the scanning resolution for an exact multiple of the nominal resolution of your scanner. If the scanner is sold for 1200 dpi, my advice would be to use only 300, 600 or 1200 dpi, and not 1000. The reson is that is the requested resolution is not the one of the scanning CCD, the scanner software has to interpolate it, and in my experience, the result can be very strange...

This also applies to some printers: it is better not to send 203.5 dots/inch if the printer asks for 200.

-- Pierre Kervella (pkervell@yahoo.com), January 03, 2002.

I had the same trouble and Microtek told me to upgrade my software. Go to the Microtek site and just download the newest. It worked for me. Cheers

-- Scott Walton (scotlynn@shore.net), January 03, 2002.

If you get a series of stripes, the answers above may apply. A single stripe is usually due to the calibration strip not being perfectly clean. On a flatbed, there is a calibration strip at the end of the flatbed plane and also one at the end of the transparency cover (easy to miss that one). They must be clear and also CLEAN. When I get a single stripe on a scan and then go back and reclean the calibration strips, that usually does it. GOOD LU

-- David Stein (DFStein@mac.com), January 03, 2002.