Beginner Metering Effect....

[Tex Gore]

Hi all,

I am trying to get my head around the metering function on my Canon EOS 6D. Does the metering only affect the 'result' of the meter reading, or does it do more? In other words, if I were to set the camera in manual mode and as such fix the shutter speed and aperture, and also the ISO, then take 3 shots all using different metering modes, would the pictures look any different?

Thanks

TG

 

[Alastair]

It depends on the subject.

If you're shooting:

• An evenly toned surface
• A surface of random tones (if you need a specific example, consider a dazzle camouflage surface)
• A head-sized dark toned target against a paler toned background
• A head-sized light toned target against a dark toned background

Then the effect of the metering mode will be apparent. I'm not going to go into what the effects would be, because it's a good thought exercise for you to think through the effect that each of the metering modes would have in each of these circumstances.


Oh.. I just spotted the semi-trick question in your post. If you fix the exposure then the metering mode won't make any difference at all. You'd need to let at least one of the parameters "float" for the camera to make the difference in the result itself (i.e. this exercise would be easier in Av or Tv modes, in M mode you'd need to change the exposure yourself to follow the metering suggestions and there's no advantage in that for this purpose).

 

[Tex Gore]

Thanks Alastair - was not supposed to be a trick question, just a way for me to fully understand what metering does, which I now do - that the different modes will indicate different exposure settings based on what you want. I understand what the metering modes are and how they work, but wasn't sure if they made some difference to how the sensor 'received' the shot as it were.

 

[Alastair]

No, the exposure parameters control how the sensor receives the shot. The metering mode guides the exposure parameters.

 

[James J]

If you use matrix metering, the whole image area is averaged to work out an optimum exposure. This can often be dominated by bright skies so can be easy to fool, but otherwise most people stick to it for most shots.

Centre weighted metering uses a circle in the centre of your image area to give heavy bias to what you are actually aiming at. A strong light source that falls into this area will dominate your meter, causing a dark photo as the light will be exposed correctly instead of the scene. When the sun is that light or you are close to a powerful light source, it really screws with the metering, but its extremely useful when a strong light is to the edge of your scene and you want to expose something like a person in a portrait with the sun to one side.

Spot metering is very similar to centre weighted, but the circle is tiny in comparison. This is extremely useful in very harshly lit scenes were you want to expose someones face properly, yet the background is either too dark or too light, that would fool centre weighted and matrix. Spot metering often dominates sport photographers choice for indoor and flood lit sports photography as it always samples what you are aiming directly at for your metering choices.

To decide on which metering choice to use, you need to think about what you want to be exposed in your shot. Spot and centre weighted metering is the usual port of call when your camera tells you how to meter a scene in matrix and it over/under exposes what you want as the point of interest.

 

[HoppyUK]

If you use matrix metering, the whole image area is averaged to work out an optimum exposure. This can often be dominated by bright skies so can be easy to fool, but otherwise most people stick to it for most shots.

Centre weighted metering uses a circle in the centre of your image area to give heavy bias to what you are actually aiming at. A strong light source that falls into this area will dominate your meter, causing a dark photo as the light will be exposed correctly instead of the scene. When the sun is that light or you are close to a powerful light source, it really screws with the metering, but its extremely useful when a strong light is to the edge of your scene and you want to expose something like a person in a portrait with the sun to one side.

Spot metering is very similar to centre weighted, but the circle is tiny in comparison. This is extremely useful in very harshly lit scenes were you want to expose someones face properly, yet the background is either too dark or too light, that would fool centre weighted and matrix. Spot metering often dominates sport photographers choice for indoor and flood lit sports photography as it always samples what you are aiming directly at for your metering choices.

To decide on which metering choice to use, you need to think about what you want to be exposed in your shot. Spot and centre weighted metering is the usual port of call when your camera tells you how to meter a scene in matrix and it over/under exposes what you want as the point of interest.

Matrix or Evaluative metering does not average out the whole image. Far from it, it's the most sophisticated metering mode with some smart intelligence. It's the camera's default mode, recommended for general shooting, and ideal for those without much experience. It's also linked to the active AF point/s so it knows where the subject is in the frame, and roughly it's distance. Centre-weighted is also pretty reliable most of the time, but spot-metering needs to be used with some knowledge and care, and best not with any auto-exposure settings.

Matrix/evaluative divides the image into dozens of different zones, and compares them all. So it knows the brightest and darkest tones, where they are, and the areas they cover. It will usually ignore small zones of extreme bright or dark, depending on their position, that might throw other metering modes. And it then applies some basic intelligence, such as a scene with a large area of brightness in the upper half of the frame, and darker below, with the lens focused on a distant point, is quite likely to be a landscape, so it will automatically apply some slight over-exposure. Matrix/evaluative is able to read quite a few common but tricky scenes in this way, a back-lit portrait might be another with predictable characteristics, and so on. It's far from infallible but usually surprisingly effective.