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  • Disclosure to Promote the Right To Information

    Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public.

    इंटरनेट मानक

    “!ान $ एक न' भारत का +नम-ण” Satyanarayan Gangaram Pitroda

    “Invent a New India Using Knowledge”

    “प0रा1 को छोड न' 5 तरफ” Jawaharlal Nehru

    “Step Out From the Old to the New”

    “जान1 का अ+धकार, जी1 का अ+धकार” Mazdoor Kisan Shakti Sangathan

    “The Right to Information, The Right to Live”

    “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता है” Bhartṛhari—Nītiśatakam

    “Knowledge is such a treasure which cannot be stolen”

    “Invent a New India Using Knowledge”

    है”ह”ह

    IS 14621 (1998): Photography - Electronic Flash Equipment - Determination of Light Output and Performance [MED 32: Photographic Equipment]

  • IS 14621 : 1998

    IS0 2827 : 1988

    Indian Standard

    PHOTOGRAPHY - ELECTRONmlC FLASH EQUIPMENT - DETERMINATION OF LIGHT

    OUT-PUT AND PERFORMANCE

    ICS 37.040.10

    0 BIS 1998

    BUREAU OF INDIAN STANDARDS MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

    NEW DELHI 110002

    November 1998 Price Group 3

  • Photographic Equipments Sectional Committee, LM 24

    NATIONAL FOREWORD

    This Indian Standard which is identical with IS0 2827 : 1988 ‘Photography - Electronic flash equipment - Determination of light output and performance’, issued by the International Organization for Standardization (ISO), was adopted by the Bureau of Indian Standards on the recommendations of the Photographic Equipments Sectional Committee and approval of the Light Mechanical Engineering Division Council.

    The text of IS0 Standard has been approved as suitable for publication as Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is drawn especially to the following:

    a) Wherever the words ‘International Standard’appear referring to this standard, they should be read as ‘Indian Standard’.

    b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker.

    In this adopted standard, reference appears to certain International Standards for which Indian Standards also exist.The coresponding Indian Standards which are to be substituted in their place are listed below along with their degree of equivalence for the editions indicated:

    In terna tional Standard

    Corresponding lndian Standard Degree of Equivalence

    IS0 1230 IS 14620 : 1998 Photography - Determination of flash guide numbers

    Identical

    IS0 5763 IS 14622 : 1998 Photography - Electronic flash equipment-Automatic control of exposure

    do

    The concerned technical committee has reviewed the provisions of IS0 1229 and IS0 3028 referred in this adopted standard and has decided that they are acceptable for use in conjunction with this standard.

    For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960 ‘Rules for rounding off numerical values (revised)‘. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

  • tS 14621:1998 IS0 2827:1988

    Indian Standard

    PHOTOGRAPHY - ELECTRONIC FLASH EQUIPMENT - DETERMINATION OF LIGHT

    OUTPUT AND PERFORMANCE

    1 Scope and field of application

    This International Standard specifies methods of measurement and sets standards of -performance for light output, angle of coverage, ready indication, recycle time and number of flashes for electronic flash equipment of the single flash type, which is primarily intended to provide illumination for photography with cameras in which the contacts that control the flashare closed when the shutter of the camera is fully or nearly fully open.

    2 References

    IS0 1229, Photography - Expendable photoflash lamps - Determination of the light output.

    IS0 1230, Photography - Determination of flash guide numbers.

    IS0 3028, Photography - Camera flash illuminants - Deter- mination of IS0 spectral distribution index IlSO/SDII.

    IS0 5763, Photography - Electronic flash equipment - Automatic control of exposure.

    3 Definitions

    For the purposes of this International Standard, the definitions given in IS0 1230 and the following definitions apply.

    3.1 flash : Pulse radiation of intense light having inconstant flux, used for photographic purpose.

    3.2 electronic flash tube : A light-transmitting envelope having electrodes and containing a gas through which the energy from a storage capacitor is discharged, therebybroduc- ing a flash of light.

    The spectral energy distribution of this light depends on the tvpe of gas and other design factors.

    3.3 electronic flash equipment : An electronic flash tube, usually mounted in a suitable reflector, and the appropriate apparatus for activating and controlling the electronic flash tube.

    3.4 automa!ic flash equipment : Equipment that varies the intensity or duration or both of a flash in such manner as to achieve the necessary exposure of the film independent of the pbject distance from the flash equipment within given limits (see IS0 5763).

    3.5 half angle of coverage : The angle between the axis of the reflector and the direction where the luminous intensity falls to one half of the value in the axis.

    On symmetrically designed reflectors the angle of coverage is equal to twice the half angle of coverage. For flash equipment producing a pattern which deviates significantly from a circle, a rectangle within which the luminous intensity does not vary by more than f 50 % from the value on the axis may be specified by two angles in horizontal and vertical directions of the rec- tangle. For large flash sources, for example studio flash sources, where the dimensions are not smaller than 2 m, the method of specifying angle of coverage is not applicable.

    3.6 light output (for bare flash tubes) : The light output measured in two mutually perpendicular equatorial lines around the bare tubes. The cross-line of the planes through the equatorial lines shall be parallelto the optical axis of the lens of the camera.

    3.7 beam light output : The time integral of the luminous intensity of flash equipment in the direction specified by the axis of the reflector, expressed ‘in candela seconds.

    3.8 stored energy (E,) : The energy stored in the main capacitor expressed in joules (watt seconds) and determined by the following formula

    where

    C is the capacitance of the combined main capacitor in farads;

    U is the peak voltage in volts (see 3.14).

    3.6 effective flash duration (tO$ : The time interval from the instant the flash reaches one-half of its peak intensity to the instant it decays to the same value.

    3.10 tota! flash duration (fc,1) : The time interval from the instant the flash reaches 10 % of its peak intensity to the instant it decays to the same value.

    1

  • IS 14521 : 1998 IS0 2827 : 1988

    3.11 Guide Number (GNI : See IS0 1230. -For flash equip-

    ment to which the inverse-square law applies, the guide

    number is a constant for a given film-speed. Guide numbers do

    not apply to flash equipment or working conditions where the

    inverse-square law does not apply, which is the case when the

    area or size of the light source is large with respect to the

    distance between source and object. This condition may exist

    for very large studio type sources (umbrellas) or in extreme

    close-up photography. Guide numbers also do not apply to

    automatic electronic flash equipment when used in the

    automatic exposure mode. For studio type equipment to which

    the inverse-square law does not apply the light output shall be

    measured at a fixed distance of 2 m and calculated into the cor-

    responding camera lensf-number based on a given film speed.

    3.12 number of flashes per battery (pertaining to equip-

    ment capab!e of operation from primary type batteries which

    are not rectlargeable) : Capacity of the equipment in terms of the total successive flashes, obtainable over a prescribed duty

    cycle, to an end point.

    The end point is reached when the ready indicator will no

    longer appear within a 60 s time period.

    NOTE - On equipment capable of changing the energy per flash by use of. for example, a power selector or exposure control system, the

    operating condi