ISO INTERNATIONAL STANDARD 12232 Third edition 2019-02 Photography Digital still cameras Determination of exposure index, IsO speed ratings, standard output sensitivity, and recommended exposure index Photographie - Appareils de prises de vue numeriques - Détermination de I'indice d'exposition, des régimes de vitesse ISO, de la sensibilité normale de sortie et de I'indice d'exposition recommandé Reference number IS0 12232:2019(E) os1 @ IS0 2019 IS0 12232:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ ISO 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +4122 749 0111 Fax: +41 22 749 09 47 Email: [email protected] Website: www.iso.org Published in Switzerland ii @ IS0 2019 - All rights reserved IS0 12232:2019(E) Contents Page Foreword ..iv Introduction. ..V 1 Scope. .1 2 Normative references ..1 3 Terms and definitions 4 Exposure index. .3 4.1 General .3 4.2 Focal plane measurement ..4 4.3 Estimating focal plane exposure from scene luminance. .4 5 Test conditions .4 5.1 General .4 5.2 Illumination 4 5.2.1 Daylight reference illuminant. .5 5.2.2 Tungsten reference illuminant 5 5.3 Temperature and relative humidity .5 5.4 White balance. .5 5.5 Infrared (IR) blocking filter. .5 5.6 Photosite integration time .5 5.7 Compression 5 5.8 Other DSC user settings. .5 6 Determination of IsO speed and IsO speed latitude .6 6.1 General .6 6.2 Saturation-based calculations. .6 6.2.1 Focal plane measurement .6 6.2.2 Sceneluminancemeasurement .7 6.3 Noise-basedcalculations 7 6.3.1 Focal plane method ..7 6.3.2 Scene luminance method .8 6.3.3 Colour cameras. .8 6.3.4 Quantization effects 6.4 Method of reporting. .9 7 Determination of standard output sensitivity (Sos) .11 7.1 Method for calculating Sos. .11 7.2 Method of reporting. 12 8 Specification of recommended exposureindex (REl) .12 8.1 General .12 8.2 Method for calculating recommended exposure index .12 8.3 Method of reporting. .12 Annex A (informative) Recommended procedure for determining the noise-based Iso speed ...15. AnnexB (informative) Sceneluminance and focal plane exposure ..17 Annex C (informative) Recommended procedure for determining SoS values. ..19 Annex D (normative) Removing low frequency variations from the image data. ..20 Bibliography ..21 @ IS0 2019 - All rights reserved iii