camSPECS express V2 is the most recent development in the camSPECS line.
camSPECS express measures the spectral sensitivity more convenient by mounting all interference filters on one "test chart."
The camSPECS express hardware consists of a metal housing with a stabilized power supply for the halogen light source. The 39 interference filters, mounted on the front plate, provide monochromatic light from 380 nm to 760 nm.
The light source is designed to ensure equal power output for the interference filters to not exceed the dynamic range of the camera. Neutral density filters in the front plate are used to compensate for possible non-uniformities of illumination.
- Illumination box with the filter panel
- Spectroradiometer EX2 for calibration
The evaluation software makes measuring fast and convenient. It calculates the spectral sensitivity with the images and the calibration data of the filters as a direct measurement, (similar to a monochromator). The software reads image files such as Tiff or common raw files* and can perform a dark frame subtraction if needed. Also possible is the evaluation of Non-Bayer pattern sensors (for example sensors with RGB-IR or RGBC pattern). In this case, all four channels are measured independently.
The primary application for the spectral sensitivities is the calculation of color correction matrices (CCM) with the CIECAM16 model and the export of ICC profiles with 2D- and 3D-MLUT rendering. An additional feature incorporates the assessment of the measurement setup by comparing real camera data with predicted RGB values.
For the calculation of individual CCMs, it is possible to apply the spectral radiance of natural objects from the in-situ database.
- Spectral sensitivity measurement
- Creation of ICC profiles
- Use of 2D- and 3D-MLUT for profile creation
- CIECAM16 implementation for profile creation
- A test procedure for evaluating CCMs with different training data
- RAW file* processing / dark frame subtraction
- Validation by comparing the camera and predicted RGB values
- Generation of color correction matrices (CCM) (RGB to XYZ and RGB to sRGB) with three different algorithms
- Calculation of white balance multipliers
- Calculation of Digital Still Camera / Sensitivity Metamerism Index (DSC/SMI)
- Visual evaluation of ICC profiles with real images
- Calibration with included Spectroradiometer
- Export of all results to XML or plain text files
Determination of CCM's (color correction matrices)
The spectral sensitivity of a camera is impressive to look at, but the real benefit is to use it to calculate the best color correction matrix for the camera. The camSPECS software comes with a module that allows the calculation of such matrices. Three different algorithms are implemented, the least squares linear regression, a white-point preserving least-squares regression and the CIECAM16 model. The required input data is the spectral response of the camera, the spectral distribution of the illumination and spectral training data.
The required training data can either be the provided spectra of a ColorChecker or measured spectra from natural objects. Image Engineering can supply access to a vast database of in situ spectral radiance data. Another option is to incorporate white balancing into the calculation of the matrices.
* In this context, we use the term "RAW file" for files that are created by a digital camera in "RAW-Mode" and are readable by the software dcraw. This does not include RAW-files that do not follow any image file format. You will have to convert these files to e.g. 16 bit Tiff first.
|Light source||Halogen (24V / 250 W) Osram 64657 HLX|
|The durability of light source||300 h|
|Color temperature||3550 K|
|Wavelength range||380 - 760 nm (10 nm steps)|
|Diameter interference filters||10 mm|
|Diameter ND filters||6 mm|
|Stabilized power supply||Automatically adjustable 100 -240 V, 50-60 Hz|
|Power input||approx. 300 W|
|Dimensions [W x H x D]||295 x 250 x 540 mm|