Is over-exposure preferable than under-exposure?

Question

I am learning the world of Photography and always attempt to get the best possible shot but there are times when getting the exposure just right can be tricky depending on the situation. (I can tell experience will be a big factor here in learning how to get the correct exposure quickly.)

Assuming you are shooting in RAW and the exposure is not correct is it better to have the shot a bit underexposed and increase the exposure in raw, have it a bit overexposed and decrease the exposure or is it the same regardless of being over or under exposed.

Answer 1

What you usually want to avoid is over-exposure. When you clip the highlights (i.e. your image has blown-out whites), you won't be able to recover any detail in these areas from the RAW file. So most of the time it is better to boost the darks with an underexposed RAW file.

Sometimes clipping is unavoidable though, depending on what you're trying to achieve with your photograph. So as a photographer you have to decide whether what you gain by over-exposure (more detail in the shadows) is worth what you lose (less detail in the highlights). Situations like: 'I don't mind that that streetlight is blown-out, because now I can clearly see the bicycle leaning against the wall in the alley'.

Answer 2

Generally speaking you should avoid over-exposure as much as possible, regardless of which format you shoot in. Once information is over-exposed details are lost and you get a bright spot in your image which gets very distracting.

Shadows are not so problematic because they are not as distracting and people expect not to be able to see in the deepest shadows.

However, exposure is an artistic decision and there are reasons when you want to over-expose on purpose such as blowing out a background to become all white. The key is that exposure has to show what you want to show in your subject. Where you want details, you can neither over-exposure nor under-exposure.

Answer 3

You don't want to lose information, first and foremost. If a photo is overexposed to pure white or underexposed to pure black ("clipped"), there's nothing you can do about that lost detail -- it's gone forever. Getting the exposure "correct" means that you capture what you need to within the range capable of being recorded by the camera. There's typically a bit of wiggle room, though. I bet you'll find that you can often overexpose or underexpose by 1/3-1/2 of a stop and not lose much or any important information.

Sometimes you'll find you have more than a little wiggle room, with the histogram showing that only 2/3rds of the range is covered by your exposure. In that case: "expose to the right," or overexpose.

The Luminous Landscape article Expose Right explains this well. Basically, 1/2 of the tonal values available in a shot are used in the first stop (the bright near-white side), 1/2 of that becomes highlights, half of that becomes midtones, half of that becomes shadows, and 1/2 of that becomes black. By this example, the darkest of areas in your photo are only made up of 128 levels of variation while the brightest are made up of 2048. In other words, a bright photo contains a lot more variation (and therefore detail) than a dark photo does. All of that extra information from the overexposed photo allows you to correct it and create a better result than an underexposed photo does.