title: The effect of time in use on the display performance of the iPad.
abstract: OBJECTIVE
  The aim of this study was to evaluate changes to the luminance, luminance uniformity and conformance to the digital imaging and communication in medicine greyscale standard display function (GSDF) as a function of time in use for the iPad.
  
  
  METHODS
  Luminance measurements of the American Association of Physicists in Medicine (AAPM) Group 18 task group (TG18) luminance uniformity and luminance test patterns (TG18-UNL and TG18-LN8) were performed using a calibrated near-range luminance meter. Nine sets of measurements were taken, where the time in use of the iPad ranged from 0 to 2500 h.
  
  
  RESULTS
  The maximum luminance (Lmax) of the display decreased (367-338 cdm(-2)) as a function of time. The minimum luminance remained constant. The maximum non-uniformity coefficient was 11%. Luminance uniformity decreased slightly as a function of time in use. The conformance of the iPad deviated from the GSDF curve at commencement of use. Deviation did not increase as a function of time in use.
  
  
  CONCLUSIONS
  This study has demonstrated that the iPad display exhibits luminance degradation typical of liquid crystal displays. The Lmax of the iPad fell below the American College of Radiology-AAPM-Society of Imaging Informatics in Medicine recommendations for primary displays (>350 cdm(-2)) at approximately 1000 h in use. The Lmax recommendation for secondary displays (>250 cdm(-2)) was exceeded during the entire study. The maximum non-uniformity coefficient did not exceed the recommendations for either primary or secondary displays. The deviation from the GSDF exceeded the recommendations of the TG18 for use as either a primary or secondary display.
  
  
  CONCLUSIONS
  The brightness, uniformity and contrast response are reasonably stable over the useful lifetime of the device; however, the device fails to meet the contrast response standard for either a primary or secondary display.
authors.affiliation: 1 Centre for Online Health, The University of Queensland, Brisbane, QLD, Australia.
authors.forename: Liam J
authors.identifier: http://orcid.org/0000-0003-1899-7534
authors.initials: LJ
authors.lastname: Caffery
authors.affiliation: 2 Radiology Informatics Support Unit, Queensland Health, Brisbane, QLD, Australia.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Manthey
authors.affiliation: 1 Centre for Online Health, The University of Queensland, Brisbane, QLD, Australia.|2 Radiology Informatics Support Unit, Queensland Health, Brisbane, QLD, Australia.
authors.forename: Lawrence H
authors.initials: LH
authors.lastname: Sim
mesh_terms: D003626:Data Display / Q000592:standards*; D006801:Humans; D050866:Liquid Crystals; D008838:Microcomputers; D013995:Time