Camera Settings; Camera Position And Lenses Used; Exposure - Image Engineering camSPECS User Manual

3.4

Camera settings

Requirements on the camera (device under test, DUT):
Set the camera to manual exposure mode. If manual mode is not available, use the automatic exposure
mode. The camera should be able to save pictures as linear raw files to get the best results.

3.4.1 Camera position and lenses used

Place the camera in front of the filter plate. The principal axis of the lens
must be aligned perpendicular to the center of the filter plate. Adjust the
distance between the lens and filter plate, so the filter plate occupies
approximately two-thirds of the field of view of the camera, centered. Avoid
using wide-angle lenses since there is a slight angle dependence of the
radiance power and the peak wavelength of the interference filters. Using
lenses with higher focal distances ensures a minimum viewing angle. Viewing angles below 15° do not
cause noticeable impacts on the resulting spectral responses.
Note:
Ensure that the filters are the only light sources captured by the camera. The pictures should be
taken in a dark room, or the space between the camera and the camSPECS box should be
shielded to avoid stray light or other light hitting the camera sensor.

3.4.2 Exposure

Set camera exposure, so the maximum recorded value of the camera capture of the filter plate is
approximately 75% of the valid encoding range. For instance, if the available encoding range is 16 bits per
channel and the valid encoding range of the image data is 12 bits per channel, set the exposure so that the
maximum value of the recorded filter plate is approximately 3000. To get correct results, the image of the
filters must not be overexposed. Take a picture with appropriate exposure settings (typically f = 5.6, t = 1/2s,
ISO 100, depending on camera and lens) in RAW mode (with Bayer pattern). Check the RAW image for the
highest recorded value in all RGB channels using a RAW image viewer or converter (i.e., dcraw).
Image Engineering
Exposure program
Aperture
ISO Speed
Auto focus
File type
Manual
No default value
Lowest value (e.g.100)
Off
RAW
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