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How RAW is "RAW"?

Cameras that address experienced users, such as D-SLR and system cameras, normally offer a RAW-Mode. In this mode, the camera puts files onto the memory device, that are called “Raw”-Files, as they contain the pure data which was obtained from the sensor and has not been processed.

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Color rendering index (CRI)

The color rendering index (CRI) is a value which expresses the degree of reproducing color of a sample to a reference illuminant. In various fields of application in video and still imaging it is necessary to reproduce colored targets. The color of an object is determined by three properties: the illuminant, the object’s reflectance and the observer. Regarding to the ability of color reproduction of different illuminants, we want to explain the meaning of the color rendering index in this TechNote.

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Converting bit-stream images

In this TechNote we would like to present three ways to convert a raw (bit-stream) image into a conventional image file format. In this case we define a raw image as a series of bits. The .raw file contains only information about the image pixel values, there’s no header and no additional information included (in contrast to the camera raw files e.g. CR2, NEF, ARW, ORF, RAF etc.).

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Have a look at the details: the open source RAW-Converter DCRAW

All D-SLRs and a lot of “Prosumer”-Compact cameras have a “RAW-Mode”. Unfortunately, the image files have a proprietary file format and the manufacturers would like the user to use their software in order to convert from RAW to an image file format like JPEG or TIFF. To get access to the data within the RAW-files, we use an open source software called dcraw by Dave Coffin.

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Precise contrast range measurement of digital cameras

TE241, TE264 or TE259 can be used to measure the opto electronic conversion function. The TE259 is a modified OECF chart following ISO 14524 and ISO 15739 using a horizontal gray scale instead of a circular one. We do highly recommend to have these standards available during measurements to be able to crosscheck the settings of your measurement setup with the standards.

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A potential way "auto exposure" can work in digital cameras

In the times of film based cameras the sensitivity of the film was characteristic for the film type selected by the photographer. This film type was produced to a specified sensitivity. Film processing had limited influence in varying the sensitivity and also the characteristic curve of the film. To get the best results the images were exposed assuming that the average scene has an overall reflection of 18% of the incident light.

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