Why does focus-and-recompose change exposure on my Olympus OM-D E-M10?

Question

When I half-press the shutter to focus on one part of a scene and then recompose, the brightness changes depending on where I focused first. For example, if I focus on a darker river and then move up to a brighter building/sky area, the final image looks too bright; if I focus on the brighter area first and then recompose toward the darker river, it looks too dark.

Why does this happen, and how can I control it intentionally on an Olympus OM-D E-M10 using autofocus?

user46366 · Accepted Answer

It sound like your camera is locking the exposure in addition to the focus when you perform a half shutter press. This would explain the overexposure when moving from a dark river to the bright sky: the camera is set to expose a dark scene properly, but it then gets pointed at a brighter scene, and subsequently over exposes. The converse is true as well, moving from a bright area of focus/exposure to an overall darker one will underexposed the image.

From what I can quickly tell on mobile, you can set one of your function buttons to AEL, which stands for auto exposure lock. Generally the way this button works is you point the camera at the object you want to properly expose, press and hold the AEL button, and then recompose to take the picture. Your manual or a Google search should provide specifics on how it works.

In your example, I would frame your final picture and lock the exposure, via AEL, so the overall image is properly exposed. Then focus on the river or building, and finally recompose to your original framing to take the photo.

In a situation like the one you describe though, generally virtually moving the focus point over the object of interest is the easiest option so that you can focus and expose in one step.

Why does focus-and-recompose change exposure on my Olympus OM-D E-M10?

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