BetterPhoto Q&A
Category: New Answers

metering????

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0 October 08, 2005

Craig-

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0 October 07, 2005

Three modes: Matrix-Center weight-Spot

Matrix metering will look at the entire scene and calculate an average..most modern cameras will look at 256 specific points spread throughout the scene.
The metering in this mode is best suited for an average scene. So what's an average scene; right? LOL
No particularly bright or dark areas you wish to reveal.

Center Weight: A greater percentage of the metering is "weighted" to the inner 8-12 percent of the center frame.

When used? Lets say you are shooting a bird at the zoo..all around and in the cage is heavily shadowed, but the bird and perhaps a few feet on all sides of the bird are fairly well lit..Center Wt will work ok.

Spot: This is actually my personal favorite.
On most cams the meter will look at the central 1-5 percent of the scene.
There are many uses.
I use it to expose the flesh tones of people..Focus and meter with the persons face dead center in the frame..You can and usually will recompose the shot after you get your reading.
Does it always work? Yes..at least to properly expose the persons face, but if your subject is wearing dark clothing, you'll probably underexpose the clothing.

What's a person to do? LOL
Craig. every scene has areas that you want to expose properly, some areas are not important to the scene.

Ex: A beautiful waterfall lit by bright sun and producing a rainbow. The waterfall is surrounded by maple trees in vibrant fall color.
Our eye sees the whole scene as it should be..but the camera does not have the ability to average the scene in time.
So how does one shoot such a scene?
There are a few ways.
If all you care about is the waterfall and the rainbow, center wt might work, as long as you meter off the water and the water is in the center of the frame.
Matrix metering will probably be fooled by the bright water and underexpose the trees.
If you meter off the trees, then you face a overexposure of the waterfall.
Hopeless isn't it? No, not at all.
There is a aperture and a shutter speed that will give the best possible shot.
Method one: Meter the trees with center wt...Take note of the reading.
Do the same with the water.
Ok..so you get 1/125th @ f/8 as an example when you meter the trees.
The waterfall reads 1/250th @ f/8
Find a shutter speed somewhere in the middle. I made up these numbers for example only, but the waterfall will no doubt be brighter than the trees.

#2) Dodging and burning.
If you only took one pic, you can selectively dodge (lighten) certain areas or burn (darken) certain areas.

#3) Here is why I love digital and post processing: I use Adobe PS..not sure what you use.

Using a tripod, shoot 2 photos..do not move the camera. For the first shot, meter the waterfall and shoot, for the second, meter for the trees and shoot.
When you edit, "sandwich" the two photos, one on top of the other..some call this layering.
Let's say you have the properly exposed waterfall on top. This means the trees look dark, BUT, the properly exposed trees are "layered" under the first photo. Remember?..Your 2nd photo exposed the trees properly.
One technique to use is called erasing.
You simply and carefully erase away the underexposed top photo of the trees to "reveal" the properly exposed trees in the photo underneath.
It sounds complex, but in reality it is not.

I hope this helps a little.
Metering is a topic dicussed by many, but now well understood by all.

One VERY important last point I failed to mention.
If the subject in your photo fills very little of the frame, but is of importance, Matrix and center wt are NOT the choice, as these two modes will NOT see the small subject, but will meter everything else but.

Shoot a white wall that fills the entire frame..Matrix, Center wt or spot will all meter properly..they have nothing else to consider.
Shoot the same white wall with a 50% outre black area..Hmmm?
Shoot a white square that only takes up 10% of the center of the frame, the remining outer area might be flowers, trees, people etc....Matrix may work since the majority of the frame is NOT the white square..center wt and spot will give too much emphasis to the white area and underexpose the people, trees etc in the outer areas.

So, what are you metering?..What is the important part you wish to meter?
How much of the subject fills the frame you are metering..all these questions are important.

Recap:
Matrix: Averages the entire scene

Center Weight: Meters off the inner 8 to 12% of the center of the frame. Varies from cam to cam

Spot: Inner 1 to 5% of frame.
Happy shooting,

Pete

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0 October 07, 2005

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0 October 08, 2005

Using spot metering (the XT has Partial metering - center 9% of the viewfinder) - one must be prepared to apply exposure compensation depending on the subject (+ for lighter than 18% gray, - for darker).

Centerweighted usually returns a good exposure since averaging the entire scene is often ~18% gray, but can be fooled by strong backlighting, dark skies/stage backgrounds, etc.

Canon's Evaluative meter (Matrix in Nikon, multi-segment in Pentax, Honeycomb pattern in Minolta, etc.) is a refinement of Centerweighted. It averages the entire scene, but gives greater weighting to the area near the active focus sensor, and also uses algorithms to apply its own exposure compensation if it senses that the scene might be lighter or darker than 18% gray. Usually very good, but can still be fooled in specific situations.

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0 October 08, 2005