ISO INTERNATIONAL STANDARD 9378 First edition 1993-09-15 Photography - Vesicular microfilm Determination of IsO speed and ISO range Photographie - Microfilm vésiculaire - Détermination de la sensibilité ISoetdel'étendueISo ISO Reference number ISO 9378:1993(E) No reproduction or networking permited without license from IHS Not for Resale ISO 9378:1993(E) Foreword ISO (the International Organization for Standardization) is a worldwide of preparing International Standards is normally carried out through IsO which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISsO, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote International Standard ISO 9378 was prepared by Technical Committee ISO/TC 42, Photography. Annexes A, B and C of this International Standard are for information only. C ISO1993 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without per- mission in writing from the publisher. International Organization for Standardization Case Postale 56 · CH-1211 Geneve 20 · Switzerland Printed in Switzerland Copyright International Organization for Standadization No reproduction or networking permitted without license from IHS Not for Resale SO9378:1993(E) Introduction This International Standard describes a method for determining the IsO speed and IsO range of vesicular microfilms used for making prints from manufacturers measure these film characteristics, which should aid users in selecting the best product for their application. Highly acceptable prints are generally obtained if the log expose range (LER) of a vesicular microfilm is equal to the effective density range of negative or positive originals. Therefore, IsO range, which is directly re- lated to LER provides a useful guide for selecting the proper product for a given effective density range, and for comparing products from various manufacturers. Vesicular photography is based on the sensitivity of aryl diazonium salt to radiation in the 350 nm to 450 nm range. Vesicular film consists of a polymeric layer in which a diazonium salt and an image-enhancing dye are violet end of the electromagnetic spectrum producesnitrogengas and colourless photolytic products. After exposure, the nitrogen gas remains temporarily entrapped in the polymer matrix and constitutes the latent image. The latent image is developed by heat which softens the polymer and allows the nitrogen to expand and form microscopic vesicles. The vesicles, which become stable and rigid when the film cools, form the image by virtue of their light-scattering nature. After development, the image is fixed by re-exposing the film to decompose the diazo salt re- maining in the unexposed areas. The nitrogen gas formed during re- exposure slowly diffuses out of the photosensitive layer without affecting the image. Since the density of vesicular film results from scattering rather than by absorption of light incident on the film, the amount of light transmitted by the film and reaching the viewing plane depends on the aperture of the projecting optics. Standard practice for densitometry established that the optical system should have an effective aperture of f/4,5. Vesicular film is used for duplicating computer output microfilm (COM) and Copyright Intenational Oorganizatin for Standardization Not for Resale