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The Users

10 people participated in this study. At the time of the interviews they were all using the Web at least 3hrs a week, with some up to 10hrs. Only one browsed regularly with images disabled, but another occasionally used a text-only browser. One had been using a text-only browser extensively to get ``a gist'' of pages but abandoned this tactic in the last year as images had become more integral to pages. Otherwise users viewed the Web through a Netscape browser of 2.2 or above; one using a black and white VDU and another a small screen. Most had access to fast network connections for which they did not pay.

Users' response to the three degraded images in the second study varied widely. Most users qualified their answers even before committing themselves to considering the images in front of them. As expected, context and purpose were determining factors: ``it depends on what the image is for'', ``surely depends on the relevance it has to the page being called''; while one person identified the size at which the picture appeared as the major issue.

A majority agreed the best quality image of the three (22Kb) was ``acceptable''. However, everyone also agreed that there were times when this was not good enough. If the purpose of finding the picture was to study the detail or to print it off, then higher quality was needed. Users also identified other kinds of images that would require better rendering: images of faces or fine art in particular.

Opinion split about the cut-off of this notional acceptability, with an increasing number rejecting the image as quality went down. Some people felt that no picture was preferable to a degraded one, while others felt that general information could still be gleaned from it. Most users mentioned either context or purpose again at this point.

One user accepted any quality of image. ``I just wouldn't look at it as long'', she said of the poorest. Another user rejected all the images: ``I'd find any quite frustrating if I was trying to look at the picture for some reason''. So a difference in general tolerance became apparent, even in a small sample.


next up previous
Next: Waiting for images Up: Image Quality Tolerance in Previous: The image

Malcolm McIlhagga
Thursday June 11 16:17:19 BST 1998