HTP increases the DR if you shoot in JPG. It underexposes by 1 stop of ISO, then lies about it in the metadata (that's why ISO 200 becomes the lowest setting - if you shoot at ISO 200 with HTP, the camera actually exposes at ISO 100). That 1-stop underexposure preserves a stop of highlights, the camera then applies a tone curve to boost everything but the highlights by 1 stop (meaning a stop more noise in the shadows).
If you shoot RAW, leave HTP off. You then have latitude to preserve >1-stop of highlights, and can apply your own tone curve.
Thanks neuro. I honestly never mess with curves. I've tried messing with it a few times or with the auto settings in DPP but never really liked the results. I normally just use contrast, highlight or blacks to adjust. Anyone have any suggestions on a tutorial for editing curves in DPP?
Canon 5D Mark II, 50D, XSi, 24-105L IS, Sigma 35 1.4, Canon 40 2.8, Canon 35 2.0, Sigma 10-20, Tamron 17-50, Canon 50 1.8, 580 EXII, 430 EXII