Light Metering Help - Canon 500D

[RobbieG]

Can someone please help me understand how the light meter works in my Canon 500D?

With my Metering Mode set to evaluative, if I change my AF point from automatic to the center point and focus on something, it appears to only meter the light for that point only leaving an overexposed shot if that focal point happens to be in the shade.

Does the camera only meter on the focus points as it appears to, and if so, is this not the same as spot metering?

What I am trying to achieve is to focus on a particular spot but have the whole frame evaluated for light as is my understanding of how evaluative light metering should work. However, if my subject happens to be slightly shaded, the rest of the shot seems to be totally overexposed.

The example pic I have attached is a disappointing shot being overexposed with the waterfall falling in the shade. This shot was taken in Program mode, ISO100 with evaluative metering and the center AF point selected. The camera selected 1/60 f5.0 overexposing the shot.

Some further experiments only seem to support my thoughts.
Example-1 was taken in Program mode ISO100 with evaluative metering. The center AF point was selected and I focused on the bright area of the lawn. The camera selected 1/100 f5.0.
Example-2 was essentially the same shot with the same settings however this time I focused on the palm frond next to the bright area of the lawn and the camera selected 1/60 f4.0 which overexposes the lawn.

When I experiment and set the AF to automatic, it is a bit hit and miss with what points are used for focus, not guaranteeing the center point but seemingly metering for the points that achieved focus.

I am a new DSLR user and am disappointed with my new camera. My G9 seems to do a better job metering so I am hopeful it is just a combination of settings I have got wrong.

Thanks in advance
Robbie

[teaking]

Your problem is dynamic range the scene of the waterfall has a very high dynamic range your eyes can adjust to this but your camera has a smaller range and so you can expose for the highlights or the shadows or do both and merge the exposures in processing.

If it helps maybe looking on google at dynamic range may help you understand a little better it is a subject that will help with many aspect of photography, what you are always trying to do is bring the light level in the shade up to or close to the light level outside the shade so in your case your going to need a very big light!!

[sk66]

Evaluative is not the same as spot nor center weighted.
In evaluative it is going to try to balance the entire scene. While the crops are almost the same for the last two images I suspect one had significantly more light area in the FOV when taken.

One of the good/bad things with DSLR is you don't have to rely on the camera to decide things for you, but that also means you can't rely on the camera.... These images would easily be adjusted with a little exposure compensation dialed in (the +/- setting).

[RobbieG]

Originally Posted by sk66

Evaluative is not the same as spot nor center weighted.
In evaluative it is going to try to balance the entire scene. While the crops are almost the same for the last two images I suspect one had significantly more light area in the FOV when taken.

One of the good/bad things with DSLR is you don't have to rely on the camera to decide things for you, but that also means you can't rely on the camera.... These images would easily be adjusted with a little exposure compensation dialed in (the +/- setting).

Thanks for your reply,
The last two images were taken as an experiment and not cropped so the light area was almost exactly the same. The only difference was the focus point was moved a couple of inches from the bright lawn to the shaded palm.
This seems to indicate to me that it is not evaluating the whole scene but just where focus was achieved.
The manual also says that when using AE Lock, it is applied at the point that achieved focus? Does this not mean that this is the same as spot metering even in evaluative mode?

[sk66]

I don't know your camera, but it sounds like it's doing "center weighted" with the center being the focus point. Look to see if there is some kind of setting for this...