BS ISO 17957:2015 pdf download

BS ISO 17957:2015 pdf download.Photography — Digital cameras — Shading measurements
4.3 Lighting
For lightness non-uniformity and luminance non-uniformity measurement, average outdoor daylight (type D) illuminant shall be used. For chrominance non-uniformity measurement and total colour non-uniformity measurement, three standard illuminants shall be used to represent the characteristics of (a) average outdoor daylight (type D), (b) indoor incandescent lighting (type A), and (c) indoor fluorescent lighting (type F). Other illuminants may be used optionally. The type of illuminant shall be reported in any case. The recommended daylight illuminant is CIE/D55 (5 503K) with a tolerance of 5 000K to 6 504K. The recommended indoor incandescent illuminant is CIE/A (2 856K) with a tolerance of 2 700K to 3 200K. The recommended fluorescent illuminant is type CIE/F2 (4 230K) with a tolerance of 3 900K to 4 600K. The light source(s) shall be positioned to provide uniform illumination and produce no glare or reflections from the target.
4.4 Test chart
The target shall provide a spectrally neutral, uniform luminance distribution over the entire imaged field of view. Spectral neutrality is achieved if the spectral transmittance or reflectance of the target does not vary by more than 5 % over the range between 420 nm and 750 nm. The construction of the target can be either transmissive or reflective. Total luminance uniformity of the lighting and the test chart is very important for this measurement. The luminance uniformity should be within 2,5 %; (i.e. [|Max- Ave|/Ave < 0,025 and |Min-Ave|/Ave < 0,025]), and shall be within 5 %; (i.e. [|Max-Ave|/Ave < 0,05 and |Min-Ave|/Ave < 0,05]) across the entire imaged area, with an average luminance between 50 cd/m 2 and 120 cd/m 2 . The light flux from the target shall be diffuse and shall not include any specular component. A target containing patterns may also be used, provided the same results as the uniform chart are obtained by performing a suitable procedure to remove the patterns. When a target containing patterns is used, exposure shall be adjusted to give an average output value of the central measurement block, between 110 and 130 in sRGB encoding values.
4.5 Image/camera settings
Exposure shall be adjusted to give an average output value of the central measurement block, between 110 and 130 in sRGB encoding values, when exposure adjustment is available. When average output values of the peripheral measurement blocks are very low (e.g. in the case of very wide-angle lens), the exposure level may be adjusted higher. The average output value of the central measurement block shall be reported in any case.