Dalle specifiche EXIF 2.21 risulta: YCbCrPositioning The position of chrominance components in relation to the luminance component. This field is designated only for JPEG compressed data or uncompressed YCbCr data. The TIFF default is 1 (centered); but when Y:Cb:Cr = 4:2:2 it is recommended in this standard that 2 (co-sited) be used to record data, in order to improve the image quality when viewed on TV systems. When this field does not exist, the reader shall assume the TIFF default. In the case of Y:Cb:Cr = 4:2:0, the TIFF default (centered) is recommended. If the reader does not have the capability of supporting both kinds of YCbCrPositioning, it shall follow the TIFF default regardless of the value in this field. It is preferable that readers be able to support both centered and co- sited positioning. Cioè (a quanto mi pare di capire) è il rapporto crominanza/luminanza sui pixel nelle foto compresse in jpg, sembra quindi essere una caratteristica dell’algoritmo di compressione jpeg della fotocamera, e come tale non credo sia modificabile. Questo è il link alle specifiche: [url]http://www.exif.org/Exif2-1.PDF[(url] [lo]
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