AS ISO 19093 pdf download

AS ISO 19093 pdf download.Photography — Digital cameras — Measuring low-light performance
3  Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .iso .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/ 3.1 handheld limit exposure time exposure time empirically considered as an upper limit to give a reasonably sharp image with handheld shooting, which is 1/f s, where f is the value of the 35 mm sensor equivalent focal length of the lens Note 1 to entry: If the camera has a mechanism for image stabilization, a longer exposure time than 1/f s for handheld shooting can still produce reasonably sharp images. 3.2 35 mm film equivalent focal length focal length of a lens attached to a camera with a sensor size of 24 mm × 36 mm (originated from 35 mm film) that produces the same field of view as the camera system with a lens at a given focal length for which the 35 mm sensor equivalent focal length is specified 3.3 full frame sensor image sensor that fills the full 24 mm × 36 mm image size of the 35 mm film format
4  Test conditions and setup
4.1  Test chart 4.1.1  Test chart and illumination The lighting condition shall be consistent with the daylight conditions specified in ISO 7589. The chart shall be uniformly illuminated in a way that minimizes stray light and specular reflection. The light source needs to be dimmable without a significant change in the spectral distribution of the light. Using a set of polarizing filters, neutral density filters or using a special spectrally tunable LED light source can achieve this. See Figure 1.Since modern still cameras provide scene-dependent image processing, the ideal approach for a low- light test is using a test chart that contains all necessary structures for evaluating the relevant image- quality parameters. The following chart is one commercially available example for such a chart. The chart shall contain at least the following structures: — a grey scale according to ISO 14524 with a contrast range of at least 100:1 and at least 16 grey levels to determine the opto-electronic conversion function (OECF) and noise performance according to ISO 14524 and ISO 15739; — a set of colour patches with at least 18 colours including colours similar to the ones mentioned in ISO 17321-1 for colour characterization. The height and width of each patch shall be greater than 2 % of the image height; — sinusoidal resolution structures in low contrast to determine the texture MTF according to ISO TS 19567-1;— a focusing aid feature consisting of concentric black and white circles at different frequencies shall be placed in the centre of the chart as shown in Figure 2; — an area of 18 % grey shall be included, and shall additionally form the background on which the other chart features are placed. Even though the current version of this document does not use them, it can be helpful to include the following optional structures: — coloured dead leaves structures for additional texture analysis on stochastic structures as described in ISO TS 19567-2; — resolution structures according to ISO 12233 to determine the modulation transfer function (MTF). The minimum active chart height shall be 675 mm, which is approximately 30 times the height of a 35 mm film equivalent “full frame” sensor. See Annex B for a detailed description of the chart.4.2  Camera settings 4.2.1  General The camera shall be fixed on a test bench during all the tests. The test needs to produce comparable results over a huge variety of different cameras. The biggest challenge is to provide a fair comparison between cameras with no control elements for the image capture (like exposure, ISO sensitivity, etc.) and cameras that require or at least allow full control over all functions and features. 4.2.2  Test lenses For low-light performance comparison of cameras with interchangeable lenses, lenses with the same open aperture and 35 mm film equivalent focal length shall be used. All cameras shall be tested at 28 mm focal length (35 mm sensor equivalent) if available. The reason for using the same equivalent focal length is to get comparable results for all cameras.