britinjapan wrote in post #17368661
- is this something that can happen, or does the camera always technically get exposure pretty much correct?
No, the camera doesn't always get exposure correct, that isn't how the meter works. The meter aims to average all the tones to a mid-grey (typically between 14-18% grey) so depending on the tones in the scene, it may expose badly. If you have a lot of white in the scene, a snowy landscape for instance, then the camera will see all that white and try and make it grey, so underexpose significantly. If you want white snow you will need to add between 1 and 2 stops of exposure to the metered exposure. When I shoot, my actual exposure may be a couple of stops more or less than the camera suggests.
If you photograph a black card and a white card, at the metered settings, they will come out looking much the same, a mid grey tone. The black card will have been significantly overexposed and the white one significantly underexposed. The meter has done its job perfectly in both cases, it is up to the photographer to compensate for significant bright or dark areas that may affect the reading. If the scene has a good spread of tones, with few bright or dark areas, then the exposure will be pretty good as metered, but the camera will adjust the exposure up or down as you recompose, as you may be including more or less bright or dark areas. This is when manual is good, as you ascertain the correct exposure and set it, then all the fluctuations are ignored.
The meter is a tool to help you assess the exposure you need to give, it does not know whether your metered subject/scene is black, white or grey and will always expose to make it grey. If you are uncertain, then take a test shot and check the histogram, then adjust exposure accordingly.