The authors studied the influence of perception time on the quantified image quality of radiographs, using as an experimental basis the target presentation time during which there was no active involvement of the observer. No change in the influence on the observer was seen down to an observation time of 1 sec.; there was a slight but practically negligible drop on further reduction to 0.5 sec. At 0.1 sec. there was a drop that would have been approximately compensated by a contrast enhancement of object detail to about twice the original value. The influence of the perception time was placed in relation to an example of the influence of structured noise on the detection performance. This influence proved to be significantly greater than that of time. A comparison of the concept of "conspicuity" as defined by Revesz and Kundel was set in relation to the term "Auffälligkeit" ("distinctiveness") coined by Stender. It was established that the quality reserve QR after Borcke corresponds to "Auffälligkeit" as defined by Stender and should best be separated from image quality changes dues to the influence of structured noise on the detection of radiological abnormalities.