The answer to this question depends if you are shooting RAW or JPEG/video. But, in both cases, you should never clip your image meaning that when looking at the histogram, both extremities should be free of any data.

Exposure leeway

RAW

RAW files have a lot of leeway regarding exposure. You can easily add or remove one or two stops (3 if you stretch it!) of exposure without compromising image quality. The reason is that RAW files store all colors and exposure information separately which make it easy to adjust after the fact.

This is the main reason why people shoot RAW: get a good initial exposure (histogram around the center area) at shooting time and get creative once you are in post production.

JPEG/Video

In these cases, the image has already been processed and all the color & exposure information are merge into a single layer. This results in much less flexibility as exposure modification drastically alters image quality. The general rule is that you can add/remove a maximum of a single stop of exposure on these and even then, it could be too much.

Over or Under expose?

The kind of histogram you should aim is a little bit over exposed. You want the exposure curve to be on the right side of the histogram to maximize details as outlined in this question. This is true for both formats but has more impact on compressed images.

But under exposed images look better!

Given the choice between an unprocessed over or under exposed picture, most people will prefer the one under-exposed because colors look more saturated and the contrast is better. And they are right! While over exposed images have more details, they have to be processed by:

  • reducing the exposure
  • boosting contrast
  • boosting saturation

Special cases

There are some exceptions to the rule above: when shooting a subject that is mostly white (think wedding dresses), it is safer to under-expose the image a bit (1/3 – 2/3 of a stop) to have more leeway with the whites in post production. Same thing with highly reflective subjects: you dont want any of the reflection to blow the highlight as soon as you adjust exposure.

Controversy

If you Google this topic, you will find that most people suggest to under expose a little bit. This is mostly due to the fear of blowing highlights. This is a good advice if you can’t work with a live histogram, the light level is constantly changing or you dont have the time to think.

But when you are in control of the situation, there are no reasons to under expose (except the special cases above).

Remember

All of the above is only valid if you dont clip the highlights or the black areas. Clipping should be your main concern when figuring out your exposure, once you are confident that nothing will clip, expose to the right.

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planetMitch

chief astronomer at planet5D LLC
Mitch "planetMitch" Aunger is the creator and mastermind behind planet5D.com — which covers every aspect of HDSLR cameras (and a whole lot of other cameras as well). A lover of photography since his early days, he graduated to selling stock photos to make a little bit of spare cash. It wasn’t much, but it allowed him to upgrade to better cameras as well as computers, and it wasn’t taking money away from feeding his family.
He loves the stories that the still image can tell. In the summer of 2008, he read a story written by Arnold Kim called “I Quit My Job” — Arn is the owner of macrumors.com. He started macrumors in 2000 as a hobby, and by 2008 he was making more money with the site than he was on his day job, so he quit. The surprise to the story is that he was a doctor making more than six figures! Right then and there, planetMitch dreamed about doing the same thing.
September 2008 rolled around, and Canon announced this new version of the incredible 5D — the Canon EOS 5D Mark II. It was the first Canon DSLR to shoot full HD video and the earth moved! (It really was a huge deal in the photography world.) planetMitch knew if there was ever a chance to ride a wave of something he was really passionate about, this was it — and the blog at planet5D.com was born. It is now one of the most popular HDSLR blogs on the planet, and he is making a full-time living from blogging. He couldn’t be happier!
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