Capture Anomalies

From UA Libraries Digital Services Planning and Documentation
Revision as of 15:21, 12 February 2013 by Kgmatheny (talk | contribs)

This page describes specific out-of-the-ordinary problems certain materials might cause during the capture process. For general guidelines in judging image quality, see Visual Assessment of Images.

Only Part of the Image is Out of Focus

Having just part of an image out of focus means one of three things

  • The image is pretty far off center on the document table
    • This could result in one or more edges of the image being fuzzy
    • To fix this, make sure the center of the image is as close as possible to the center of the camera's focus, which is the center of the grid or overlay in the EOS Utility.
  • The camera isn't far enough from the image to take a quality picture
    • This will result in an image that is uniformly fuzzy around the edges (assuming it's centered and has been auto-focused to that same center)
    • To fix this, move the camera up and/or switch to a capture station which allows for a greater distance between camera and document table.
  • The camera isn't centered properly on the document table
    • This will result in a gradient effect across the image, with one side/corner being in focus, with less focus as it approaches the opposite side/corner
    • To fix this, the camera will need to be physically readjusted -- the lens is no longer parallel to the document table. Please see Jeremiah for help with this.

Moiré Patterns

This is a kind of pattern that sometimes appears in digital images, involving rainbow lines or dots showing up against an actual pattern in the object itself. Here are a couple of examples:

Check out her hair:


Look closely at his forehead:


When can this happen?

This might affect materials that

  • are off-set printed, and
  • contain pictures and/or graphics
  • Examples may include: posters, pamphlets, booklets, cards, newspapers

This will NOT effect

  • handwritten materials
  • photocopied materials
  • photographs (note: photographs that have been printed as above are a different matter)

How do we deal with the problem?

Be aware. It will happen. Know the kind of collections/materials it is likely to impact (more modern collections with more professionally produced materials), and be extra vigilant with examining your captures as you go, to make sure it's not happening.

  • If a moiré pattern does appear in test scans, try one of the following things:
    • rotate the object until -- hopefully -- the effect disappears; or
    • change the distance between the camera and the object (move the camera or elevate the object) by at least a few inches.
  • If you can't get rid of the moiré pattern as the object is being captured, there are a couple of post-production fixes that can be employed.
    • First, try the Moiré Reduction tool in Photoshop's Camera Raw interface (in Graduated Filter mode, it will show up as a slider in the third set of tools)
    • If all else fails, you'll need to do the corrections manually in Photoshop; see Jeremiah for instructions on how to do this