Light metering modes

[Goldcoin79]

Hi

I Would like to know about different situations for setting the light metering modes if any one could give there opinions. I have read about them and worked out that for portrait pictures you would likely use spot metering and for scene pictures you would use evaluative metering.

What else would you look for to decide what light metering mode you would use and what situations evaluative, centre weighted and spot metering would be used in?

 

[table1349]

Understanding Camera Metering and Exposure

Introduction to Metering Modes

Metering Modes Explained

Exploring Metering Modes

Camera Metering Modes by Digital Photo Secrets

 

[KmH]

What make/model camera? Your profile doesn't indicate it.

 

[TCampbell]

I'm guessing it's a Canon based on the names of the modes.

"evaluative" says the camera meters the at every metering point it has but THEN looks for a recognizable patterns in the metering. Based on this, it has a database of common patterns -- so it can guess, for example, that you're probably shooting a portrait, or a landscape, etc. It then uses the database to bias the metering to the points that are most important. That's why they call it "evaluative".

While that sounds really smart (and often it is), it's certainly not foolproof. There are lots of conditions that can fool the camera. In those situations I switch to "spot" metering and then carefully meter some element in the scene that I'm reasonably confident would register as a "middle gray". If the shot is _really_ important, I'll take out a hand-held incident light meter -- you really can't fool an "incident" light meter, but you can easily fool a "reflected" light meter (which is what the camera has to use.)

And here's another tip... if you really care about the exposure, but find that the $200-300 (or $700) for a dedicated quality "incident" light meter is a bit expensive, you can actually use a middle-gray card (the same card used to set white balance.) This is because the reflectivity of the card is a known quantity. Say you're taking a photo but your subject is dressed in clothing that you know is going to throw the meter -- and you needed to white balance the shot anyway. Just hand them the gray card, fill the frame with the gray card and take a meter reading of the card. THAT is the right amount of light for the exposure. Manually lock in that exposure and get rid of the gray card and shoot the set (ignoring whatever the meter may tell you as long as the lighting conditions don't change.) A gray card can be fairly inexpensive. You can even order gray cards in 12% or 18% gray depending on your camera's calibration (I think most modern cameras are now calibrated to 12% middle gray, so a 12% card would probably be the card for you in that case.)

My own rules are:

If the shot has a LOT of dynamic range (e.g. a landscape has a LOT of dynamic range between the whitest puffy cloud and the deepest darkest shadow in a valley or chasm; a concert hall is almost completely black apart from the fairly bright lights highlighting the performers.) These shots that demand a lot of dynamic range will be the hardest to nail (and you definitely need to use RAW when shooting them.) In this case, you can (a) switch to spot metering and manually meter the critical points (e.g. the performers face) or (b) take a few sample readings of the brightest point you can find and the darkest point you can find then manually calculate the exposure halfway between the two.

If the shot does NOT have a lot of dynamic range then you can more safely use evaluative metering and not worry too much. Even if the evaluative mode misses the correct exposure by a full stop you'll still get the whole image safely within the dynamic range of the camera so you can easily adjust this in post.

If the shot qualifies as a "low key" (lots of black & darkness) or "high key" (lots of whites) or your subjects are wearing black or white clothes then the reflected light meter in the camera won't get an accurate reading. Switch to "spot" metering and carefully target a critical exposure point (such as the subject's face.)

Whenever exposure is critical, shoot in RAW. This gives you the greatest amount of adjustment latitude and least risk of losing data due to clipping.

 

[EDL]

The links provided by gryphonslair99 are pretty good at explaining it.

It's really not difficult once you read those. I assimilated metering modes as the area of the entire frame the camera is trying to expose for.

Spot - means the exposure is going to get set so that small portion of the frame will come out properly exposed...and the camera ignores everything else around it.

Center weighted - the camera will consider exposure for a larger area of the frame but will give the most consideration to the center area.

Evaluative (Canon), or Matrix (Nikon) - the camera tries to see everything in the frame and adjust exposure so it all comes out.

Now, that doesn't necessarily tell you what your photo is going to look like. I found that setting up a shot, then taking photos of it and changing the metering mode really told me the most about the effect. I'm a kinesthetic learner, so I tend to pick up things faster by doing than by reading....that's not to say I wouldn't read about it first, but doing it gives me the most feedback and I learn most from that.

As for when you would use each, that depends on what you want your photo to end up like. Landscape might favor matrix because you typically are trying to get the entire frame exposed correctly. Situations like maybe a car shot might favor center weighted...you are trying to get a smaller area than the entire frame correct to emphasize the car. Spot is very useful, but typically you will use it in situations that have large variances in light within the frame and you want to be sure to get the subject right and ignore the rest. The face of a model, for example, or someone's face when they are back lit, or if you are shooting into the sun and want a small subject exposed correctly. That doesn't mean that any time you are shooting into the sun you must use spot, you might decide you want a silhouette instead. use matrix then so the bright sun isn't blown out, this in turn will make the subject way under exposed..i.e. silhouetted.

If you are shooting still life, aren't in a hurry or don't need to get it right the first shot, you can even shoot aperture, or shutter pri, or manual and just take several shots making adjustments in between to get the desired effect too. That's the beauty of digital, shoot away like a mad man and delete what you don't like.

 

[Goldcoin79]

Thanks for all the advice it's very helpful. My camera is a cannon powershot SX 30 IS.

 

[Goldcoin79]

Just been reading up on light metering from the links above and I am a bit confused about a statement that was made, maybe I am missing something and some one can help.

The statement said "Metering tells the camera how much light there is in the scene, and from that it works out how long to keep the shutter open to correctly expose the image" At the moment I mainly use Tv mode or Av mode which I though as the user of the camera I adjust the exposure by either adjusting the shutter speed or aperture and the iso and in manual mode the user adjusts all 3 settings to get the right exposure.

Please tell me what it means by the metering modes adjusts the exposure. I understood it as the metering mode selected tells the camera what part of the picture you want exposure to concentrate on.

 

[KmH]

In Tv and Av mode the settings the camera is assigned to choose are necessarily based on the light meter reading.

Consequently, the metering mode you have selected also has a bearing on the setting decisions the camera is going to make.

Evaluative metering mode samples 100% of the scene in the viewfinder, while Spot metering mode samples less than 5% of the scene where ever that spot is doing the sampleing.

Note that your Canon (not cannon) camera likely has the spot used for Spot metering confined to the center of the scene, just like many of Canon's DSLR cameras.

Nikon DSLR cameras allow the user to move the spot around to the same positions as the camera's auto focus sensor locations in the scene.

 

[Goldcoin79]

I know the difference between the light metering setting but here is where I have slight confusion. If I was in manual mode the way I see it is I set the exposure by adjusting the shutter speed, aperture ans iso so would I be right in saying that depending on what light metering mode I set depends on where that exposure is concentrated on?

 

[unpopular]

Proper use of spot metering is the only mode you need to make precise exposure decisions, the others are just there for your convenience.

I almost exclusively use spot meter mode.