If you prefer the less-contrasty tone curve that we used with earlier Canon models such as the 5D, 5D II, and 5D III, then as pointed out above, the most precise way to achieve that is to use the DNG Profile Editor, open a 5Ds / 5Ds R image (previously converted to DNG), and change the Base Tone Curve setting in the Tone Curve tab from Base Profile to Camera Raw Default. Then Export the new profile (File menu -> Export Profile...) and you can use that instead. You can even make it your default profile, if you like. As for Camera Standard and the others have higher-contrast tone curves than before ... well, those are designed to match the in-camera behavior (or Canon's own image processing routines in their desktop software, Digital Photo Professional). Thus, if you feel the DPP-based raw conversions for the 5Ds / 5Ds R have too much contrast, that's feedback I recommend you provide to Canon. In other words, we don't design the shape of the tone curves for Canon's Picture Styles -- Canon does.
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