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« on: July 16, 2014, 11:13:38 PM »
Frank, try developing the raw files as JPEGS with 100% quality.
I used to always use 16 bit TIFF images as input to PhotoScan. The images were obtained by "developing" RAW files. But after some experimentation and comparisons I switched to using JPEG images with "quality" of 100%. These images are also obtained by "developing" RAW files, and are not the JPEG images output by the camera. My comparisons showed that using 100% quality JPEG images results in a decrease of a few percent in the number of sparse points, and does not have a noticeable impact on the PhotoScan results. JPEG images with lower quality settings are smaller but result in fewer sparse points and sufficiently low settings of quality resulted in noticeable impact on PhotoScan results.
All JPEG images are compressed, and as RalfH noted above the compression can result in artifacts and loss of data. But not all JPEG images are the same. The algorithm used for generating JPEGs has an input parameter called "quality" which can range up to 100%. Higher quality values result in fewer artifacts, less loss of detail but larger files. Generally the quality setting used internally in a camera to generate JPEGs is not available but is selected to keep file sizes relatively small.
16 bit TIFFs from raw files from my Canon T1i/500D are 86.3 MB. JPEGs with quality set to 100% range from 10 MB to 21 MB depending on image quality. (The corresponding JPEGs direct from the camera with unknown "quality" setting range from 4 MB to 6 MB.)
Creating the JPEGs by "developing" the raw files allows me to correct for chromatic aberration, adjust the exposure and contrast if needed while avoiding clipping in the areas of interest, and select the JPEG quality setting.