I’ve been struggling with lightroom issues of late, and this is to do with how Canon and Lightroom handle RAW files differently. Trawling the web others seem to have the same issue. RAW files look darker in Lightroom than they do in the image preview on the camera and how Canon’s DPP program renders them. After some research, I discovered that this is mainly due to the color profile Adobe uses for RAW files and the difference between that and what the camera uses. For RAW files, Lightroom uses the Prophoto RGB colourspace to render all files. Most cameras would probably be using sRGB colourspace. Because Prophoto is a wider colour gamut than sRGB the colour values are different and to have them in that range they appear darker. sRGB has a more compressed colourspace and hence the colours appear slightly brighter for the same colour values.
I now do a few things to remedy this issue. First, turn off all image enhancements in the camera. This includes setting your picture style to neutral or whatever the closest equivalant on your camera is. Disable any auto-lighting controls in the camera. For canon this is the auto lighting optimiser. Shoot in the AdobeRGB colourspace or, if you have it, Prophoto. All these things together will render a preview image closer to what Lightroom would see in the RAW file. This will also give a more comparable histogram.
NOTE: If you go back to shooting jpeg, you may want to change your in-camera develop settings back to what you usually would use otherwise your jpegs may come out looking a bit funny.
The next step is to create a develop preset in Lightroom. Note, this applies to Lightroom 3 as it’s what I use. For older versions you may have to do it differentrly or it may not be available. In the develop module, go down the bottom of the controls list to the camera calibration settings. For the preset you should choose ‘Camera neutral’ and under the tone curve set it to linear. Next you need to save that as a new preset selecting only the tone curve and calibration settings. Once this is done you can set the preset to apply during your next import.
The other option that works is to first convert all your RAW files using the manufacturer’s processing program and outputting them as TIFF files for later editing in lightroom. Canon use Digital Photo Professional (DPP).
I hope this helps some people.