Actually there is more potential for recovery with slight overexposure, than there is with underexposure. Look at it this way... Underexposure in a digital file, making shadow areas too dark, is a lack of data. Overexposure makes for excessive data in highlights. So you are better off slightly overexposed than underexposed.
Emphasis on the word "slightly" though... Too much and it will be clipped and unrecoverable. But there is more "headroom" in the highlights of digital files, than there is in the shadows. Particularly the way Canon cameras meter and expose.
The world as seen through our eyes is up to 10 stops dynamic range. I agree our DSLRs do not capture more than 6 to 8 stops at best (probably less a lot of the time)... leaving some clipping at either end, or piling it up more strongly at one end or the other.
There are several ways to deal with this, to essentially compress the dynamic range into the capabilities of the camera, computer, software, printers, ink and paper.
1. Filters used at the time of exposure.
2. Careful adjustments to a single image in post processing.
2. HDR techniques combining two or more images taken at the time of exposure.
4. HDR techniques using multiple copies of an image post processed differently.
5. A combination of several of these.
ETTR or "Expose to the Right" is largely a bandaid for auto exposure shooters, but also can be applied in principle to manual exposures if using the camera's built in metering system. It basically concludes that Canon cameras tend to err a little toward underexposure, probably to prevent highlight blowouts and to some extent a carryover from the days of slide film. There's actually more data available to recover detail in highlights, more "headroom" in the image files so it's better to slightly overexpose, than to underexpose. Doing so also minimizes noise, which is amped up any time an image's exposure is increased in post processing.
For more info, see http://www.luminous-landscape.com …optimizing_exposure.shtml
and http://www.luminous-landscape.com/tutorials/expose-right.shtml
Also, it's very important to use prints to judge DR, not your computer monitor. Even the very best graphics quality monitor clips DR on both ends (typical consumer monitors, laptop screens, etc. are even worse). A high quality printer with the right inks and paper will bring out a great deal more detail than you might think was in the image when looking at it on your computer monitor, both in highlights and in shadow. I'm often surprised how much more detail there is at both ends fo the DR range in a print, than I saw on the excellent monitor I use to post-process my images.
This is nothing new, by the way. The dynamic range of digital imaging is about the same as it was with most transparency film... Except it's just the opposite in that with slide film the blocked up shadows are an excess of "data" and blown out highlights are a lack of "data" on the film. Color negative or color print film is the opposite and it's characteristics and processing give a bit more dynamic range than slide film.
Black and white film also has limited range, but is the most within the user's control if they do their own processing start to finish and carefully employ a method such as the Zone System. Using those techniques, we measured with 1 degree spot meters to establish the dynamic range of the scene before us, made our exposures accordingly, placing the tonalities where we wanted them. Then back in the lab we used time and temperature to carefully control the film development to best match the DR of the scene. Later when making the print we matched paper, exposure and print development accordingly. Fred Picker was at the heart of creating the Zone System techniques... Ansel Adams and many others made extensive use of them and took the system farther or adapted it to better meet their own particular needs.
There was a Color Zone System, too... but it is more limited in nature. Probably in large part because not a lot of people did their own color film processing (it cost a lot more to set up a color darkroom, more of the work needs to be done in total darkness, temperature needs to be much more precisely control, and some of the chemicals were pretty nasty)
Hey, photography isn't easy! Hell, if it were, everyone would do it!
Oh wait, looks like practically everyone is these days... hmmmmm.
Okay, good photography isn't easy!
