1、BSI Standards Publication Photography Digital cameras Texture reproduction measurements Part 1: Frequency characteristics measurements using cyclic pattern PD ISO/TS 19567-1:2016National foreword This Published Document is the UK implementation of ISO/TS 19567-1:2016. The UK participation in its pre
2、paration was entrusted to Technical Committee CPW/42, Photography. A list of organizations represented on this committee can be obtained on request to its secretary. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct applica
3、tion. The British Standards Institution 2016. Published by BSI Standards Limited 2016 ISBN 978 0 580 88589 1 ICS 37.040.10 Compliance with a British Standard cannot confer immunity from legal obligations. This Published Document was published under the authority of the Standards Policy and Strategy
4、Committee on 30 April 2016. Amendments/corrigenda issued since publication Date Text affected PUBLISHED DOCUMENT PD ISO/TS 19567-1:2016 ISO 2016 Photography Digital cameras Texture reproduction measurements Part 1: Frequency characteristics measurements using cyclic pattern Photographie Camras numri
5、ques Mesurages de la reproduction de la texture Partie 1: Mesurages des caractristiques de frquence en utlisant un modle cyclique TECHNICAL SPECIFICATION ISO/TS 19567-1 Reference number ISO/TS 19567-1:2016(E) First edition 2016-04-01 PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E)ii ISO 2016 All right
6、s reserved COPYRIGHT PROTECTED DOCUMENT ISO 2016, Published in Switzerland All rights reserved. Unless otherwise specified, 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
7、 an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISOs member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 copyri
8、ghtiso.org www.iso.org PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E)Foreword iv Introduction v 1 Scope . 1 2 Normative references 1 3 T erms and definitions . 1 4 Test conditions . 1 4.1 General . 1 4.2 Environments for measurement 2 4.3 Apparatus and hardware 2 4.4 Arrangement of measuring equipmen
9、t . 2 4.4.1 Reflective test chart . 2 4.4.2 Transmissive test chart 2 4.5 Lighting 3 4.6 Camera settings 3 5 Texture reproduction measurement procedure . 4 5.1 General . 4 5.2 Multiburst measurement . 5 5.2.1 Low contrast multiburst chart . 5 5.2.2 Measurement method . 6 5.3 Siemens star measurement
10、 7 5.3.1 Low contrast sine siemens star chart 7 5.3.2 Measurement method . 7 6 Presentations of results 8 6.1 General . 8 6.2 Multiburst measurement . 8 6.3 Siemens star measurements . 8 Annex A (informative) Categorization of texture10 Annex B (informative) Exposure condition for the measurement .1
11、1 Annex C (informative) Interpretation of measurement results 14 Annex D (informative) Measurement results of multiburst and siemens star 16 Bibliography .20 ISO 2016 All rights reserved iii Contents Page PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E) Foreword ISO (the International Organization for
12、Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the r
13、ight to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. The procedu
14、res used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial
15、rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights id
16、entified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents). Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement. For an explanat
17、ion on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISOs adherence to the WTO principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information The committee responsible for this documen
18、t is ISO/TC 42, Photography.iv ISO 2016 All rights reserved PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E) Introduction Texture generally means the visual and tactile surface quality derived from the physicality of the material and the roughness or graininess of the surface. For digital still cameras
19、, texture is of course the visual surface quality and the characteristic of texture reproduction in the captured image is interpreted into the reproduction of the low contrast fine details. This Technical Specification specifies the measurement of how cameras reproduce texture defined as low contras
20、t fine details. The tendency to utilize small sensors with high pixel counts in some cameras leaves a very small amount of light reaching the individual pixel. With the signal getting smaller and the noise level remaining at a certain level, it is necessary to reduce the noise in the image processin
21、g after capturing the image. Although the algorithms used for noise reduction have been developed over time, they are still not able to differentiate texture in the actual scene from the unwanted noise introduced by the capturing system. This decreases the image quality and it is therefore helpful t
22、o have a method to measure the loss of texture. Texture can also be enhanced to increase the acutance of the image. The texture reproduction is dependent on frequency and contrast because the noise reduction and the acutance enhancement, etc. are nonlinearly dependent on the pixel value and the diff
23、erence among the surrounding pixels. This part of ISO 19567 specifies methods to measure texture reproduction using test charts with cyclic patterns. The test charts are based on the established measurement methods, multiburst (IEC 61146- 1) and siemens star (ISO 12233). This part of ISO 19567 newly
24、 defines the density of the test charts and exposure setting of measured cameras. The measurement results are presented in the spatial frequency response (SFR) curves. If one SFR is larger than the other in all frequency range, larger amount of texture is reproduced in the corresponding image. If tw
25、o SFRs have a cross point and the larger SFR depends on the frequency range, the superior image in the subjective evaluation is dependent on the dominant frequency of the image. Comparison of the measurement result provides important information in the texture comparison of the captured images. Text
26、ure in a real scene consists mostly of non-structured or random patterns as shown in Annex A. Although it has been confirmed by experiments (Annex C and Annex D) that the texture reproduction characteristics of most cameras are well represented by the measurements in this Technical Specification, so
27、me cameras are found to indicate different characteristics for structured patterns compared to those for non-structured patterns. Measurement methods using non-structured or random patterns are under study and are expected to be included in consequent parts to this Technical Specification. ISO 2016
28、All rights reserved v PD ISO/TS 19567-1:2016 Photography Digital cameras Texture reproduction measurements Part 1: Frequency characteristics measurements using cyclic pattern 1 Scope This part of ISO 19567 specifies a protocol to measure the texture reproduction in the images captured and processed
29、by digital cameras including cameras in other devices, e.g. in camera phones. This part of ISO 19567 specifies protocols for the measurement of the texture reproduction using test charts with cyclic pattern. This part of ISO 19567 excludes the acceptable range of value for texture reproduction. 2 No
30、rmative references The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendment
31、s) applies. IEC 61966-2-1:1999, Multimedia systems and equipment Colour measurement and management Part 2-1: Colour management Default RGB colour space sRGB IEC 61966-2-1/Amd 1:2003, Multimedia systems and equipment Colour measurement and management Part 2-1: Colour management Default RGB colour spa
32、ce sRGB 3 T erms a nd definiti ons For the purposes of this document, the following terms and definitions apply. 3.1 texture low contrast fine details, which appear in objects EXAMPLE Low contrast fine details, which is visible in foliage, fur, sand, textiles, grass, or masonry surfaces. 3.2 texture
33、 reproduction response in the output image of cameras to the texture of the object in the scene 4 Test conditions 4.1 General The following measurement conditions should be used as nominal conditions when measuring the texture reproduction of a digital camera. TECHNICAL SPECIFICATION ISO/TS 19567-1:
34、2016(E) ISO 2016 All rights reserved 1 PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E) 4.2 Environments for measurement The measurement shall be carried out in the following environment unless otherwise stated: Temperature: 23 C 3 C 4.3 Apparatus and hardware Either a reflective chart or a transmissiv
35、e chart may be used. The light flux from the target shall be diffused and shall not include any specular component. 4.4 Arrangement of measuring equipment 4.4.1 R eflecti v e t est chart The arrangement of the measuring equipment for a reflective test chart shall be set up as shown in Figure 1. The
36、camera shall be positioned so that it casts no shadow on the chart. The lamps shall be positioned at an angle which avoids direct specular reflection from the test chart entering the camera. f F i g u r e 1 A r r a n g e m e n t o f m e a s u r i n g e q u i p m e n t f o r r e f l e c t i v e t e s
37、 t c h a r t 4.4.2 Transmissive test chart The arrangement of the measuring equipment for a transmissive test chart shall be set up as shown in Figure 2.2 ISO 2016 All rights reserved PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E) Figure 2 Arrangement of measuring equipment for transmissive test char
38、t 4.5 Lighting Colour temperature of illumination shall be 5 700 K 1 000 K. Any illuminance level of the test chart may be applied for the texture reproduction measurement; however, the illuminance level in the range from 1 000 lx to 2 000 lx (in the case of transmissive chart, from 57,3 cd/m2 to 11
39、5 cd/m2 for 18 % gray) is recommended when the measurement has no specified purpose (e.g. low light performance). Non-uniformity of illumination on the chart shall be less than 10 %. The light source(s) should be positioned to provide uniform illumination and produce no glare or specular reflections
40、 from the target. A flickering light source is not recommended as it may cause banding artefacts to occur in the captured image. In the case of using a flickering light source, although it is not recommended, the exposure time shall not be shorter than one period of the flickering to minimize the ba
41、nding artefacts caused by the light source. 4.6 Camera settings The exposure should be adjusted to give the output value for the background gray near the centre of the measured chart to be the value corresponding to the input value defined below in the cameras output colour space. (input luminance f
42、or gray) = (max input luminance) (gray reflectance) For sRGB cameras, the output Y for 18 % gray is 118 (8-bit). The deviation of the exposure should be between +5 % and 10 % of the aforementioned target exposure. For example, the mean output luminance Y value for the 18 % gray should be 118 (8-bit)
43、 +2, 6 when the output colour space of the camera is sRGB 8-bit (IEC 61966-2-1 and IEC 61966-2-1/Amd 1). The exposure shall be in the range of the aforementioned deviation when the measurement results of multiple cameras are compared (Annex B explains the basic concept for this stipulation). The exp
44、osure may be adjusted by the exposure bias setting of the camera or by adding a white or black card to the test chart. White balance should be adjusted to render the centre of the image, as neutral as possible. The focusing shall be in the best practically attainable focus. For a camera with user se
45、lectable compression ratio (e.g. JPEG), the compression ratio should be minimum to minimize the artefacts of compression. The texture reproduction for RAW format image ISO 2016 All rights reserved 3 PD ISO/TS 19567-1:2016 ISO/TS 19567-1:2016(E) data should be measured for the output of the RAW conve
46、rter software. The name and the setting of the RAW converter shall be reported with the results of the measurement. Other settings, such as “sharpness”, “noise reduction”, shall be in the default mode (factory shipping condition) if those settings are not reported. 5 Texture reproduction measurement
47、 procedure 5.1 General Texture reproduction is measured by the amplitude of a sine waveform in this part of ISO 19567. The frequency characteristics of the texture reproduction are measured for various frequencies in the sine chart to be captured. Two measurement methods, the multiburst and siemens
48、star, are defined in this part of ISO 19567. The multiburst chart consists of several low contrast sine waves of discrete frequency (see Figure 3). Each sine wave consists of multiple cyclic patterns along a single direction in the multiburst chart. The siemens star chart consists of a low contrast
49、sine wave-modulated star burst pattern (see Figure 4), which includes continuous frequency variation in all directions. Based on the structure of each chart, the multiburst and the siemens star can be used in the cases shown in Table 1. Table 1 Guidance for selecting the measurement Multiburst Siemens star (1) In the case of measuring SFR with verification of the waveform and the amplitude of the captured image. (11) In the case when skilled engineer recognizes the SFR approximately from the
