This standard specifies the determination of ISO sensitivity of black-and-white photographic negative films. This standard applies to films processed using general chemicals and equipment, but also to films processed by special processes, such as using activator developers or thermal developers. This standard does not apply to films for cinematography, aerial photography, plate printing, radiography and microphotography, nor to negatives of diffusion transfer systems. GB/T 2923-1995 Determination of ISO sensitivity of black-and-white photographic negative/processing combinations GB/T2923-1995 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
ISO
Deterinination of ISO speed of hlack-and-white pictorial still camera negative filmm/process systemsGB/T 2923—1995
ISO 6—1993
Replaces GB 2923—82
This national standard is equivalent to the international standard ISO6--1993 Photography—Photographic negative film/process systems—Determination of ISO sensitivity.
Generally speaking, black-and-white films can usually produce good results under several different product formulations and processing conditions. At this time, the sensitivity depends on the processing conditions used. In other words, a film will produce several sensitivity changes when using different processing conditions. Therefore, this standard specifies the method for determining the sensitivity of small film market combination systems. The standard recognizes that black-and-white film does not have a single sensitivity value if different processing methods are used, which is different from the traditional practice of giving a single sensitivity value for a product. In the future, the processing conditions used to determine the film sensitivity should be clearly stated to avoid misunderstandings. Since users do not know how to develop the film in their hands, film manufacturers have the obligation to provide a sensitivity that can achieve good results. Usually, manufacturers use the film's over-noise tolerance to give a conservative sensitivity to prevent users from using low-sensitivity processing technology to cause under-noise.
Taking into account that film sensitivity depends on the degree of development, the brightness range of the scene, the conditions of the subject and the printing paper, etc., this standard now defines the sensitivity of the film/processing combination system as determined when the film is developed and controlled at a specified contrast level. In other words, the sensitivity ranking of several films in different processing control systems is often different. Using an exposure meter that complies with ISO2720 or ISO2721, The correct noise effect can be obtained by averaging the scene and processing it according to the standard development requirements. 1 Subject content and scope of application
This standard specifies the determination of the sensitivity of black self-negative film (ISC) for photography. This standard is applicable to films processed using general chemicals and equipment, but it is also applicable to films processed by special processes, such as thermal development using activator developer drums.
This standard does not apply to film for cinematography, aerial photography, plate printing, radiography and microphotography, nor does it apply to films for film processing, such as film ... Negative film suitable for diffusion transfer system.
2 Reference standards
GB1150 Geometric conditions for photographic transmission density measurement GB11501 Spectral conditions for photographic density measurement GB1S06 General rules for photosensitivity determination of silver salt photosensitive materials Part 1 Noise conditions for samples applicable to incandescent tungsten lamps and simulated moonlight
3 Definitions
3.1 Exposure (H)
Integral of illuminance on film over twilight time, measured in ixs, represented by the symbol F. State Bureau of Technical Supervision 1995-12-20 Approved for implementation on August 1, 1996
3.2 Sensitivity (S)
GB/T2923-1995
The determination or expression of the response of a photosensitive material to radiant energy under specified conditions of exposure, processing and density measurement. 4 Sampling and storage
When determining the ISO sensitivity of a product, the first consideration is whether the results measured by the sample taken can represent the average sensitivity used by users. This requires regular testing of products of different batches under the conditions specified in this standard. Before measurement, the samples should be stored under the conditions recommended by the manufacturer for a period of time to simulate the average period of normal use of the product. It is also necessary to conduct multiple independent tests to ensure that the test equipment and process have been accurately calibrated. The purpose of the above provisions is to ensure that the obtained film properties represent the performance when used by the photographer. 5 Test method
5.1 Principle
The samples are exposed and processed as specified below, the density value is measured from the resulting image, and the sensitivity characteristic curve is drawn. The sensitivity is evaluated and calculated from the curve.
5.2 Safety
In order to eliminate the possible influence of all unnecessary light radiation on the sensitivity measurement, sampling. Exposure and processing should be carried out under completely safe conditions
5.3 Irradiation
According to the provisions of GB150G1, the exposure time can be selected between 1/1000~~5s. 5.4 Processing
5.4.1 Sample balance
During the interval between exposure and processing, the sample should be kept in an environment with a temperature of 23±2 and a relative humidity of (50±5)%. Amateur films should be processed within 5~10 days after exposure. Professional films should be processed within 4h~7d. 5.4.2 Processing Specifications
Since there are many types of equipment and chemicals used in the processing of black and white films, this standard does not make specific regulations on processing equipment and chemicals, but only limits the slope of the processing, that is, the density difference △D between the two points m2~n is 0.80 (see 5.6.3 and the figure below). Generally, the sensitivity provided by the film manufacturer can ensure that its film can obtain the specified results according to its recommended processing conditions. The processing data can be obtained from the film manufacturer or other units that provide 180 sensitivity. It includes the processing procedures and the required chemicals, time, temperature, stirring equipment and all additional information to obtain the required sensitivity measurement results. The film sensitivity measured by different processing techniques may vary greatly. For a certain film, different sensitivities can be obtained by changing the processing technology, but with the change of sensitivity, other sensitive properties and physical properties will also change. Generally speaking, since intensive processing and adding Ding can increase the sensitivity, it will also increase the graininess of the negative film and the final printed positive film. 5. 5 Density measurement
Use a densitometer that meets the geometric and spectral conditions specified in GB 11500 and GB11501 to measure the standard visual transmission density of the processed image. The reading should be taken in the uniform development area. 5.6 Evaluation
5.6.1 Sensitometric curve
Use the standard visual transmission density as the ordinate and the logarithm of the corresponding light intensity with a base of 10 as the abscissa to draw a sensitivity characteristic curve, as shown in the figure below.
5.6.2 Minimum density
Along with the exposed sample for determining the sensitivity characteristic line, process a sample of the same film that has not been exposed, and measure its density, which is the minimum density of the film (including fog density and film base density). 5.6.3 Determination of the reference point of sensitivity The method for determining the ISO sensitivity of black and white negative film is shown in the figure below. Point m is located 0.10 above the minimum density on the characteristic curve. Point m is located at the position of "GB/T 2923—1995
On the characteristic curve, the logarithm of the corresponding noise light quantity (base 10) increases by 1.30 units compared with point m. The development degree of the sample is controlled at a density difference (D) of 0.80 between the two points m. At this time, the exposure H corresponding to point m is the reference noise light disc for obtaining the sensitivity. The recommended method for obtaining the sensitivity is shown in Appendix A (reference).
5.6.4 Sensitivity calculation formula
The sensitivity is calculated according to formula (1) or formula (2):
S - 0.80/11.
S° - 1 + 10lg(0. 8/Hm)bzxz.net
Arithmetic value sensitivity.
In the formula: s
S° is the logarithmic sensitivity;
H. The noise light quantity at the reference sensitivity point is calculated. Ix·s. 3.0
6 Product Grading
6.1 ISO Sensitivity Scale
Sensitivity Determination Method Schematic Diagram
Quantity (Base Additive or Calculated Density)
Sensitivity should be graded in rounds. The arithmetic and logarithmic sensitivities of black and white photographic negatives are graded in rounds according to the following table. .
·（2）
- 2 25
2 Product ISO Sensitivity
GB/T2923—1995
1S() Sensitivity
To determine the ISO sensitivity of a product (different from an individual sample), the sensitivity should be measured from different batches of products according to the sampling, storage and test conditions specified in this standard. The arithmetic average of the multiple lgH values ​​obtained is used for rounding and grading, and the nominal sensitivity of the product is determined using the above table.
6.3 Uncertainty
CB/T 2923--1995
The instruments and processing techniques used to determine the film sensitivity should be calibrated to ensure that the error of Ig1}fm is less than 0.05. Product marking and labeling
The sensitivity of black and white photographic negative film can be expressed in one of the following three forms: a. arithmetic sensitivity value, such as 1s0100: b. logarithmic sensitivity value, such as ISo 21
c.It is expressed using both arithmetic sensitivity values ​​and logarithmic sensitivity values, such as ISO100/21°. Since sensitivity depends on the exposure light source, noise level time, and processing, in addition to indicating the sensitivity value on the product label, the light source, noise level time, and processing technology used to determine the ISO sensitivity should also be clearly stated to avoid misunderstanding in actual application. GB/T 2923—1995
Appendix A
Recommended method for determining 1gH
(reference)
First, make characteristic curves of different development degrees of the test film, and on each curve, find the logarithmic value 1gH of the warm light quantity corresponding to the density point 0.10 above the minimum density (as the horizontal axis), and the corresponding point where the noise light quantity increases by 1.30 logarithmic units compared with the point, and then calculate the density of the above two points (as the vertical axis), and then draw the A~H change curve (appropriately smoothed), and determine the base noise light level H. for obtaining the sensitivity from the intersection of this curve and the horizontal point of 8, see Figure A1. .
.3. 25
Additional remarks:
Method for determining H.. in Figure A1
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the First Film Factory of China Lucky Film Company. 204
This standard was drafted by China Electronics Research Institute, China Lucky Film Company First Film Institute, and the Photosensitive Materials Inspection Center of the Ministry of Chemical Industry. The main drafters of this standard were Mou Xiufang, Tang Zhijian, and Pu Zeng.
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