Monday, 17 November 2008

Kent Wedding Photographer - Exposure Compensation


1/400, f/2.8, ISO 1250, -1 EV, 200mm (70-200mm f/2.8 L IS)

1/80, f/2.8, ISO 3200, +1 EV, 16mm (16-35mm f/2.8 L)

Since including EXIF data with photos I've had a few questions about exposure compensation. Before reading the following I recommend you first check out the posts on metering and exposure, exposure values, and an earlier post on exposure compensation.

Cameras meter using reflected light and are programmed to assume that the average reflectance for a scene is 18% (equivalent to a middle grey tonality). The result of this is that all scenes will have middle grey tonality unless you compensate for, or bias, the exposure.

If a scene is darker in tone, you need to reduce the exposure so that the scene remains darker, and is not over-exposed as middle grey.

If a scene is lighter in tone, you need to increase the exposure so that the scene remains lighter, and is not under-exposed as middle grey.

Most scenes do have mid-grey tonality (which is why cameras are programmed this way) but the essential skill to develop is to recognise when they don't. A couple of examples for you.

In the top shot I felt that tones darker than middle grey predominated so I reduced the exposure by one stop (-1 EV) to avoid over-exposure. In the bottom shot lighter tones predominated, so I increased the exposure by one stop (+1 EV) to avoid under-exposure. It takes time to get a feel for how much to adjust exposure by - like many things in life, it's a question of practice.

An alternative method is to spot-meter a small area in the scene which has middle grey tonality. Whichever method you chose, however, requires you to develop your eye for tonality. This is an essential skill to develop as a photographer. It truly does lead to enlightenment!

Check out my photography here: Kent wedding photographer


George Bain said...

David, how about using the histogram to make this judgement?

I also read that on the 5DMk2 you could use the liveview to adjust your exposure and see the difference realtime. Thoughts?

David said...

Hi George,

If you've got the time during a shoot then the histogram is a very valuable aid. At a portrait session I will always do this. At a wedding, however, I never do. I'm too busy keeping an eye on my subjects!

I can't imagine this workflow changing with the 5D Mark II but we'll have to wait and see. I have a very open mind!



Samuel said...


Using the histogram or EV adjustment both take time. In a high pressure environment like a wedding how about just leaving the camera on AEB +1 / -1. Combined with RAW headroom, I imagine you can't go wrong?

You'll need more memory card storage but for unrepeatable shoots - worth doing?

Thank you

David said...

Hi Samuel,

An interesting thought. In response I'd say:

1. Once you 'get your eye in' exposure compensation is as quick as adjusting for aperture. It becomes instinctive.

2. It will be more difficult to react to the moment with the camera having to work 3 times as hard.

3. You'll need to change your memory card 3 times as frequently. A real nuisance.

4. 3 times as many shots to look though afterwards - too much of a burden on workflow.

It's much easier all round to try and get things right in camera.



Jim said...

... in addition, AEB does not work if your flash is turned on.