1、INTERNATIONAL STANDARD 10157 First edition 1991-06-15 Corrected and reprinted 1991-09-15 Photography - Flash exposure meter - Requirements Photographic - Exposimetre pour flash - Prescriptions Reference number IS0 10157:1991(E) IS0 10157:1991(E) Foreword IS0 (the International Organization for Stand
2、ardization) is a worldwide federation of national standards bodies (IS0 member bodies). The work of preparing International Standards is normally carried out through IS0 technical committees. Each member body interested in a subject for which a technical committee has been established has the right
3、to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with ISO, also take part in the work. IS0 collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft Internat
4、ional Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an lnter- national Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard IS0 10157 was prepared by Technical Committee ISO/TC 42, Photo
5、graphy. Annex A of this International Standard is for information only. 83 IS0 1991 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 permission in writing from the publi
6、sher. International Organization for Standardization Case Postale 56 l CH-1211 Geneve 20 l Switzerland Printed in Switzerland ii INTERNATIONAL STANDARD IS0 10157:1991(E) Photography - Flash exposure meter - Requirements I Scope This International Standard applies to photoelectric flash exposure mete
7、rs which measure the time in- tegral of the luminance or of the illuminance of a photographic object (to be called thereafter “object”) illuminated by a source of light for a brief illumination period l) and indicate the time integral or a number corresponding to the time integral or thefinumber req
8、uired for the correct exposure of a photographic film with a given speed. Continuous light, which is available in addition to the light emitted by the flash light source, is also evalu- ated. NOTE 1 If the object is illuminated by electronic flash equipment with automatic exposure control, the measu
9、r- ing results of the flash exposure meter can deviate from the calibration values of the flash equipment. 2 Normative references The following standards contain provisions which, through reference in this text, constitute provisions of this International Standard. At the time of publi- cation, the
10、editions indicated were valid. All stan- dards are subject to revision, and parties to agreements based on this International Standard are encouraged to investigate the possibility of ap- plying the most recent editions of the standards in- dicated below. Members of IEC and IS0 maintain registers of
11、 currently valid International Standards. IS0 2720:1974, Photography - General purpose photographic exposure meters (photoelectric type - Guide to product specification. IEC 68-2-6: 1960, Basic environmental testing pro- cedures for electrkaI components and electronic equipment - Part 2: Tests - Tes
12、t F: Vibration. IEC 348: 1971, Safety requirements for electronic measuring apparatus. 3 Definitions For the purposes of this International Standard, the following definitions apply. 3.1 luminance coefficient, 4: The luminance coef- ficient, 4, is the ratio of the luminance, I, of the sample for a g
13、iven observation direction to the illuminance, E, on the sample (q = L/E). 3.2 gate time: The gate time of the measuring cir- cuit is the time in which the flash light meter is measuring. 3.3 storage time: The storage time is that time after the end of the gate time in which the indicated value chan
14、ges by Ifi 7 % corresponding to + l/IO I$*). 3.4 acceptance angle: See definition in IS0 2720. 4 Scales Relative aperture scale, exposure time scale and film speed scale are to be selected in accordance with IS0 2720. 5 General characteristic quantities of the flash exposure meter 5.1 Measuring rang
15、e It is recommended that the measuring range be in- dicated in candela seconds per square metre when measuring the time integral of luminance of the ob- ject and in lux seconds when measuring the time integral of illuminance of the object. In addition, the aperture range and the luminous time (flash
16、 duration) range are to be indicated, in 1) Wthin the range of gate time specified by the manufacturer for the specific meter. 2) E,= Exposure value. IS0 10157:1991 (E) which a measurement of flash light at an IS0 100/21 film speed is possible. 5.2 Gate time During the gate time both the light of th
17、e flash light source and the light of the surroundings (continuous light) are to be measured. It is recommended that the times of the exposure time scale be used in ac- cordance with IS0 2720. If there is only one fixed gate time, it must not be less than 0,00781 s and is to be indicated. If the fla
18、sh exposure meter does not, or does not completely, evaluate continuous light, this fact is also to be indicated. 5.3 Storage time If the meter incorporates an automatic switching-off circuit, the storage time shall be long enough so that the meter indication can be read. The storage time shall be i
19、ndicated on the exposure meter or in the instruction booklet. 6 Calibration 6.1 Measuring method For calibration or for checking the calibration, known exposures are produced and compared with the in- dication of the flash exposure meter when measur- ing the light at the same place as the acceptance
20、 device of the flash exposure meter. 6.2 Light source The calibration of flash exposure meters is to be checked with a light source of the correlated colour temperature of 5 500 K+ 200 K. It must be possible to set the duration of the light source, one-tenth of the time value, to between 0,8 x lo-2
21、s and 3,o x 10-4 s. 6.3 Measuring the light which falls upon the object 5.4 Addition of individual measurements If the measuring values of individual measurements are or can be added with the flash exposure meter, the deviation from the sum of four single flashes (provided there is a constant radiat
22、ion from the flash light source) must not be greater than 1/5FW. 55 . Acceptance angle The acceptance angles are measured in accordance with IS0 2720. 5.6 Spectral response The spectral response of the photoelectric receiver shall show no discontinuities within the visible spectrum (380 nm to 780 nm
23、). The ratio of the indications of the receiver, including optical elements, for a luminance of the distribution temperature of 4 700 K compared with that of the CIE standard illuminant C (representing daylight with a correlated colour temperature of 6774 K), shall be 1 1$ (corresponding to + l/3 JE
24、dt is the time integral of illuminance, E, in lux . f A is the f-number; is the arithmetic IS0 film speed; 7 0 c is the logarithmic IS0 film speed; c- 7 J is a constant which can be selected by the manufacturer in the range of 210 1x-s to 420 1x-s for the given type of exposure meter. NOTE 3 The ref
25、lectance of the object, which is con- sidered to be a uniform diffuser, is assumed to be 0,18. If a reflected-light type flash exposure meter is to be designed, the calibration constant (C) can be deter- mined by using the reflectance of the object. 2 IS0 10157:1991(E) 7 Measuring accuracy 7.1 Error
26、 limits of the indication The combined effect of calibration temperature, hu- midity, storage condition, exposure, vibration ex- posure, shock exposure, position, and flash duration shall not cause the indication to vary by more than + 3/4&Z, from the nominal value. - 7.2 Flash duration and illumina
27、nce Within the time range between 8 x IO-3 s and IO-4 s and the illuminance range between 5 x IO* lx and 2 x 106 lx, the meter shall give the same indi- cation with a tolerance of + l/3&, for the same amount of the time integral of illuminance. 8 Influence of external measuring conditions 8.1 Temper
28、ature range The values indicated by the flash exposure meter, at temperatures of between 0 OC and 40 OC, com- bined with other effects, must not differ by more than the tolerance given in 7.1 from the values of the calibration formulae in 6.2 and 6.3. 8.2 Effect of humidity The influence of the humi
29、dity is expressed as a modification of the exposure indication at 40 OC Ifr 5 “C and (90 + 5) % relative humidity. Following the exposure to high humidity for 48 h and prior to taking measurements, the flash exposure meter shall be stored for 2 h at 23 OC + 3 OC and (65 + 20) % relative humidity. Th
30、e modification of the climate must be carried out slowly so that the dew point is not reached. 9 Wlechanlcal strength Requirements and testing shall be in accordance with IEC 348. 9.1 Requirements The apparatus shall have adequate mechanical strength. The components shall be reliably fastened and se
31、cured. The electrical connections shall be re- liable. Internal wiring shall be installed in such a manner that its insulation cannot be damaged. These requirements should be especially con- sidered for apparatus containing sources of vi- bration or shock, and safety measures should be taken against
32、 influences on other assemblies. Compl iance is checked by inspection and by per- formin g the following tes ts. The tests described in 9.2 and 9.3 shall be performed on portable apparatus. For other apparatus, these tests are recommended but are optional. The tests are based on the assumption that
33、labora- tory or industrial use of the apparatus causes no abnormal stress. These tests may not be sufficient for apparatus such as that used in vehicles. 9.2 Fall test The apparatus shall be fixed in its position of normal use to a hardwood board and shall be dropped flatly three times on to a hardw
34、ood plate having a mass of at least three times the falling mass. The test set-up shall be in accordance with IEC 348:1971, fig- ure 5, and the drop height shall be in accordance with table I of this International Standard. Table 1 - Drop height Falling mass I kg Drop height Less than 10 10 to 50 Mo
35、re than 50 9.3 Vibration test Apparatus shall be subjected to vibration endurance conditioning by frequency sweeping as specified in IEC 68-2-6. The apparatus is fastened in its normal position of use to the vibration generator by means of straps around the enclosure. The direction of vibration is v
36、ertical, and the conditions are as follows: Duration: 30 min Amplitude (peak-to- 0,35 mm peak): Sweep frequency range: 10 Hz - 55 Hz - 10 Hz Sweep rate: Approximately one octave per minute IS0 10157:1991(E) 9.4 Blow test IEC 348:1971, figure 6. The hammer shall be applied to any external part that,
37、when broken, is likely to The apparatus is held firmly against a rigid support expose live parts, including handles, levers, knobs, and shall be subjected to sets of three blows from and the like, by pressing the hammer nose a spring-operated impact hammer as shown in perpendicularly to the surface
38、of that part. IS0 10157:1991(E) Annex A (informative) Bibliography IS0 1230:1973, Photography - Determination of f7ash guide numbers. IS0 2721:1982, Photography - Cameras - Automatic controk of exposure. C3 c4 C5 IS0 2827:1988, Photography - Electronic f7ash equipment - Determination of light output
39、 and performance. IS0 5763:1989, Photography - Electronic flash equipment - Automatic control of exposure. CIE Publication No.15:1971, Calorimetry. IS0 10157:1991(E) -P-P UDC 771 m376.35 Descriptors: photography, photographic equipment, tests, mechanical tests, drop tests, vibration tests, exposure meters, impact tests. photographic exposure meters, specifications, calibration,
