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[The good news:]

Hi everyone!

If you ever been an owner of DxO Software, you would agree with me that there is no way of doing anything in the software with dual_iso-dng. That is a real problem especially when you do not want to have such a heavy peace of software as Adobe Photoshop is. Thus, there is only one option after making dual_iso shots: BACK into cr2!

Well, at first, it looks completely impossible - private Canon RAW file format and the result of the cr2hdr, which is not only in dng format, but also has 16 bits per sample instead of 14 bps. However, is it really unfeasible?

The good news: No, it is NOT unfeasible. I did it. There is no trouble in replacing the RAW data in a CR2-file. Not at all. It works fine in the DxO Optics Pro now!

The bad news: I need help. It turns out that the raw values in the dng-result are not that simple to convert them back into 14 bps. SHR by 2 creates something really dark with a strange tint of green although the bright areas look perfectly normal. It just means that I need a proper transformation from the cr2hdr resulting color space into Canon original color space. Therefore, I would appreciate it if someone could help me to write the proper transformation in C. The problem is the black level which does not correspond to the original one from cr2. I will have to dig into the cr2hdr sources.