Photographic wanderings

• French

I think you already have taken some pictures of snowy landscapes in winter or summer beach that are very under-exposed? For those who love a nice deep skies are generally pleased, but the rest of the picture is disappointing.

Why does this result happened although the software in the camera usually gives good results? Why is this under-exposed? How to fix this problem?

The answer lies in the method of light measurement made ​​by the camera.

Before the measuring cells of the light was on-board cameras, it was common to see the photographer out a small device, put themselves in the place of his subject, measured light and assign the value data to perform the shot. He was performing an incidental measure of light: it determined the light falling on the subject. If the light conditions did not change or slightly, these settings were kept for the series of shots.

Measuring cells embedded on our cameras (from point-and-shoot to SLR) proceed differently: it measures reflected light. The exposure is determined based on light reflected by the subject by considering that the average measured over the entire image (or depending on the measuring mode: matrix, center weighted ; Rée, spot) must correspond to a 18% gray.

The result with a default setting, a white wall will come out gray.

So if your image contains a large “clear” (or, on the contrary, “very dark”), the cell “to deceive”.

And how do I correct this little problem (for snow or the beach)?

On a point-and-shoot camera, there are at least a Snow scene mode or range.
On an SLR or other camera with advanced settings, with exposure compensation, you must overexpose with 1 to 2 stops).

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