The ISO standards often specify requirements for the surrounding conditions when testing a camera. As the ISO group for Photography tries to keep these requirements consistent for all standards we summarize the important aspects in this "TechNote".
Temperature:
The temperature should be kept in the range of 23°C +/- 2°C. When designing the air conditioning system please keep the power consumption and heat generation of the chart illumination in mind.
Humidity:
The humidity needs to be within (60 +/- 10)% rh.
Wall and floor:
Reflections from surrounding surfaces should not impact the measurement. Therefore it is recommended to paint the walls in neutral colors. To avoid flare and stray light in the scenes it is best to use a dark gray or even better a matte black for walls, ceiling, and floors. Since it is difficult to get a suitable material a mid to dark gray is usually sufficient for the floors.
The material the floor is made of needs to be rock solid to avoid camera motion. Otherwise e.g. people walking through the room may cause significant shake. Also keep aspects in mind that may cause a building to shake like nearby railway tracks, freeways, or low flying airplanes.
Room size:
The statement is “it depends …”. Not many standards specify a target size but the timing standard (ISO 15781) does. It specifies a height that is 30 times 24 mm the height of the 35 mm format. That results in a target height of 720 mm and a target width of 1080 mm for a 3:2 aspect ratio. This format is close to our A 1066 format.
For a target that size we have found that placing the illumination on each side of the target at 45° and at least 1.5 meter from the target leads to good results for uniform illumination. This setup and taking the diffusor size of the lamp into account results in a minimum width of the room of 4.5 meters.
The length of the room depends on the longest focal length that needs to be tested. For a room that is app. 10m long the maximum focal length that can be tested is 10,000 mm / 30 = 333 mm (35mm equivalent).
The room height depends on the operating height and the chart mounting. For our horizontal chart mount a standard height of 2.5 m is sufficient. However we prefer the vertical mount because it avoids touching the test charts and allows automatic chart exchange. In this case a minimum height of 3 m is required.
Power supply:
The required power supply depends mostly on the kind and power of the illumination sources and on the air conditioning system.
Illumination:
All light sources that are not used to illuminate the test charts need to be turned off during the measurement. Depending on the location even the reflection of markings for emergency exits can cause unwanted effects in the measurements.