However, aside from the technical explanation regarding the camera's screen only showing a jpeg output of the captured data I had never had an issue with my antique Nikon D70 with the highlights ON and I am shooting RAW 100% of the time. Once I see blinkers on the shot I took, a reduction on the exposure would give me reliable results comparing these 2 successive shots when I opened them up in Lightroom. I am not so sure about Canon cameras but I am pretty sure that David Ziser is a Canon guy shooting with both a 5D Mk II and a 7D. I merely recommended his setup since I both have the video of the training and the book about shooting weddings. A full explanation and benefit for Canon shooters to activate this feature on the camera whether you are a RAW or pure JPEG shooter can be found in his book at pages 18 -25. Cheers.