Clarification on Spot Metering

[TheArcane]

I am trying to make sure I have a full grasp on how spot metering works. If I am understanding it correctly, you select "spot metering" on your camera, which would be the center focus point on mine. I then point that center focus point at something in the scene which is equal to about 18% gray, adjust my exposure, recompose the scene to how I want it, and fire the shot? It is basically just letting me select the 18% gray tone to adjust my exposure to, instead of trusting the camera to do an average of the entire scene. However the camera itself isn't actually doing anything extra after I fire the shot, correct?

[tclune]

Correct.

[russellsnr]

Hi, You may find this helpful
http://spotmetering.com/spwhy.htm
Russ

[DanK]

yes, but it has nothing to do with the AF spot, which can be both a different shape and a different size than the metering spot. Your manual should have a diagram showing how large it is. It is typically circular, not cross shaped.

[TheArcane]

yes, but it has nothing to do with the AF spot, which can be both a different shape and a different size than the metering spot. Your manual should have a diagram showing how large it is. It is typically circular, not cross shaped.

It is in the area of the center focus point, either way you're point your center focus point on the area.

[Colin Southern]

Spot metering a middle gray subject and then recomposing etc is one way - but the other is to spot meter whatever you like, and then manually enter in the variation from a middle gray.

Eg if you spot meter something white, then ensure your meter is pointing to two stops over the centre mark.

I wrote an article on it a while back - take a look at "links to useful & informative threads" post at the top of the Community Lounge forum (sorry, would link to it, but just on iPhone at the moment).

[DanK]

Re Colin's suggestion--an old trick that I have used for decades is to hold your palm so that it has the same lighting as the surface you want to meter, take a reading, and open up one stop. Depends on complexion, of course.

You should check your manual to get an idea of the size of the area. the following is from the manual from my camera (Canon 50D). On this camera, it's a larger area than you might guess.

[Inkanyezi]

I am not quite sure, but I do believe that the spot meter was conceived in order to do selective metering for using the zone system to evaluate the scene. That is how I learned it in the sixties, and I also think that Ansel Adams at the time used spot metering as well.

I sometimes use spot metering, but more often I use the averaged method with compensation for scene brightness. The result is the same although the method is different, as I mostly chimp with highlight warning to see what parts of the image that are close to burning out or burned out and adjust exposure accordingly. Spot metering requires the measured area to be large enough to be relevant and often those highlights are too small for the spot meter.

With my camera, anything above +2 would mean a blocked highlight, so when I spot meter a highlight, I set compensation to +2 if I intend it to touch the limit of what the camera might register. With other cameras, the compensation might be different, it has to be tried out.

Trying to find that "middle grey" in a scene is futile in my opinion. The method of pointing the meter to your hand will work just as using the Weston Invercone of the Sekonic dome for incident light. It works for landscape and most other outdoor shooting, but it is not what the spot meter was conceived for in the first place.

The spot meter is an instrument that can help visualisation of a scene, as you can use it to find the span of brightness within the scene. Hence if you find the brightness range larger than the range of your sensor, you will know that some of the detail either in highlights or shadows will be lost, and you can decide where. Spot metering will of course also confirm that a scene with less dynamic range will fall into the range of your sensor. However, for most of my photography I find extensive use of all aspects of the zone system a bit too time consuming without helping me to get any better images, so I only do it occasionally, and mostly I just concentrate on the brightest highlight where I wish to preserve detail. Then spot metering is highly efficient and swift. I just set compensation to +2, aim at the highlight and lock exposure.

[William W]

. . . you select "spot metering" on your camera. . . then point that center focus point at something in the scene which is equal to about 18% gray, adjust my exposure, recompose the scene to how I want it, and fire the shot?

I would suggest you ask youself - 'why am I choosing to use Spot Metering?'

I use Spot Metering quite often, but I mostly do NOT use only one meter reading within the scene: but rather usually use three, at least two and sometimes four.

To have the ability to easily make distinct meter readings within a scene and then to manually compute the exposure is the most usual reason why I choose to use Spot Metering, in the first place.

WW