ImagingTips.com

Scanning Tips

by Wren McMains
(Updated 10/11/2009)

It doesn't matter what scanner you have, here are some basic recommendations:

  1. Use your scanner's TWAIN interface (your scanner may have some push button, or other interface that seems simple to use, but my experience is that the defaults are NEVER set to give you a high enough quality image). Each scanner's TWAIN interface is different, but samples from two different scanners can be found on these pages: Scanning from FastStone and Epson V750 Pro Scanner.
  2. Be sure to use the "Advanced Mode" (or whatever your scanner calls it) so you can see the size of the resulting image (in pixels) before you start the scan.
  3. Scan at HIGH resolution for archiving, use FastStone to create lower-res versions for websites, e-mailing, etc.
  4. Most scanner interfaces automatically apply some sharpening to the image, if you're comfortable sharpening an image yourself, TURN OFF the sharpening done by the scanner. You can do a much better job (but it's another step you really need to do at some point after any other enhancements).

The key to scanning is the resolution of the resulting image. The scanner works in dpi (dots per inch) based on the size of the image you're scanning. What's really important is the size of the image (in pixels) you end up with. You probably know the resolution of your camera (in mega-pixels, or Mpix), you want to end up with a scanned image of a similar resolution. You certainly don't want an image of less than 3 Mpix, I recommend 6-12 Mpix as a minimum for archiving.

The table below will help you relate a scanned image size in pixels to Mpix:

Original Size
in Inches
Scanned at Scanned Size
in Pixels
Mpix
8 x 10 200 dpi 2,000 x 1,600 3
4 x 6 400 dpi 2,400 x 1,600 3.7
5 x 7.5 400 dpi 3,000 x 2,000 6
8 x 10 300 dpi 3,000 x 2,400 7
8 x 10 400 dpi 4,000 x 3,200 12
8 x 10 600 dpi 6,000 x 4,800 27.5
8 x 10 800 dpi 8,000 x 6,400 49
4 x 6 600 dpi 3,600 x 2,400 8
4 x 6 800 dpi 4,800 x 3,200 15
4 x 6 1200 dpi 7,200 x 4,800 33
3 x 5 600 dpi 3,000 x 2,100 6
3 x 5 800 dpi 4,000 x 2,700 10
3 x 5 1200 dpi 6,000 x 4,200 24
35mm film 3200 dpi 4,000 x 2,600 12
35mm film 4800 dpi 6,000 x 4,000 24
35mm film 6400 dpi 8,100 x 5,400 48

When scanning slides I normally don't recommend going above the native resolution of your scanner (which may only be 1600 dpi or less). The values of the dots are interpreted at resolutions above the native resolution. (My good scanner has a native resolution of 6400 dpi and has interpreted resolutions of 9600 and 12,800 dpi.)

Constraints: The higher the dpi, the longer it takes to scan. Very large images (24-48 Mpix) require a lot of computing power to work with, but for archival purposes I recommend scanning at as high a resolution as your computer can handle with reasonable speed.

My Recommendations:

8 x 10 prints 400-800 dpi
5 x 7 prints 400-800 dpi
4 x 6 prints 600-1200 dpi
3 x 5 prints 600-1200 dpi
35mm film 3200-6400 dpi

Problem Areas:

  1. Printed Material (books, magazines, newspapers, postcards, etc.): These images have been "screened" (turned into dots of varying sizes for the printing press) ... you need a scanner interface with a "de-screening" option for these images to look any good ... inexpensive scanners may not have this option.
  2. Photos printed on Linen, Satin or Pearl paper: The texture of the paper shows up in the scan ... I haven't found a good solution ... let me know if you do. I've had the best luck scanning at very high resolutions and then down-sizing. Photos printed on glossy or matte paper don't have this problem ... they will scan as well as film.
  3. Faded or Dis-colored Images: Scanner interface may have options to correct, but I think you can do better using Photoshop.
  4. Dust/Dirt on Slides or Negatives: High-end scanners come with software called "Digital ICE" which automatically cleans them after scanning.

One last tip: Some scanners come with software that let's you customize exactly what happens when you press the "scan button" on the scanner. If yours does, it's worth the effort to figure out that works when you want to do "production" scanning (scanning lots of the same size images). Probably not as easy as it should be, and different for every scanner so I can't really help you.


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Copyright Wren McMains, 2009