How do I separate focus and exposure on a Canon 700D when recomposing, and why is the background overexposed?
Asked 3/6/2016
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I’m using a Canon 700D in Program mode with a single AF point, usually the center point. I half-press the shutter to focus on a person, then recompose to include a brighter building in the background before taking the shot. The subject looks OK, but the background becomes very washed out.
Is this expected because the camera is exposing for the subject? Can I improve this by separating autofocus and metering—such as focusing on the face first, then recomposing and metering from the final frame? How would I do that on the 700D, and is there a better approach for balancing a darker subject against a brighter background?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
10y ago
2 Answers
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You can manually adjust exposure compensation, use exposure bracketing or use the high-dynamic range setting, which will internally combine a number of images made with different exposures into one JPEG.
My personal choice would be to use exposure bracketing, as that allows you to select one image, or if no single image has the required dynamic range, to combine them afterwards in post-processing.
That said, you can adjust the gamma (exposure curve) in your existing photo to improve the image with tools such as Adobe Elements or (free) IrfanView.
The trouble with relying on auto-exposure in one area and auto-exposure in another area is that it leaves you trying to move the camera around while the scene may be changing. It's best to preset a manual exposure override in that situation.
Originally by user35542. Source · Licensed CC BY-SA 4.0
user35542
10y ago
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Yes—this is expected if the subject is much darker than the background. The camera exposes for one balance, so exposing the person correctly can blow out the bright building; exposing the building correctly can make the person too dark.
Separating focus and exposure can help with recomposing, but it does not solve the dynamic-range problem by itself. On the 700D you can use AE lock (*) to lock exposure, and you can also move AF to a separate button (back-button focus via C.Fn-6) so focus and exposure are controlled independently.
For a better-balanced result, your options are:
- use AE lock or back-button focus so you can meter and focus separately when recomposing
- apply exposure compensation if the camera’s auto exposure is too bright
- use exposure bracketing or the camera’s HDR mode
- set a manual exposure if the scene is stable
- add light to the subject with flash, ideally off-camera, so both subject and background fit within the exposure range
If you already have the photo, editing the tone curve/gamma may recover some balance if highlight detail still exists.
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