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Old Dec 24, 2008, 10:27 PM   #1
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i have been out of dslr photography for a while and would like to get back into it with my pentax dslr.

just a couple general questions:

1. when should you use the different AE metering selections?
- multi-segment
- center weighted
- spot metering

2. advantages and when to use polarized and circular polarized filters.

thanks.

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Old Dec 25, 2008, 3:42 AM   #2
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lgbalfa wrote:
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i have been out of dslr photography for a while and would like to get back into it with my pentax dslr.

just a couple general questions:

1. when should you use the different AE metering selections?
- multi-segment
- center weighted
- spot metering

2. advantages and when to use polarized and circular polarized filters.

thanks.
Most modern AE metering systems integrate multi-segment to handle a generally problematic scene. It's like a simple solution when taking mere snapshots and you don't want your subject to be over or under-exposed along with whatever background lighting there is.

About the polarizer: today's AF systems require the Circular Polarizer as Linear Polarizers tend to interfere with AF sensors.

That's about the simplest way I can put it. I'll leave it up to the techies to elaborate.
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Old Dec 25, 2008, 4:58 PM   #3
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As far as the exposure options - multi-segment takes the whole picture, divides it up into sections, meters each section and averages the exposure required for the whole scene. Cameras assume that the proper exposure would be a mid-grey for as much of the scene as possible. This is fine for many situations, especially general quick snaps on the street, a lot of travel photography and might do as well as possible if the scene has too much dynamic range. It's those times when I sometimes don't like it - it can blow out highlights that I really want exposed properly to allow detail in shadows that I don't care about. But it's not a bad option for casual situations (though I tend to rarely use it).

Center weighted does something similar, except the center part of the frame is given more weight than the rest of the scene. This means that if you put those highlights you don't want blown in the center, the camera takes that into account so won't blow out the highlights. I tend to use this quite a bit, but it has it's disadvantages too. If you have a tendency to use the center point for focusing, then re-frame to put the subject somewhere else in the frame, the camera can expose for the background instead of the subject (the Pentax cameras do offer the option of setting the camera so that the exposure is locked at the same time as the focus, nice if you use this method for shooting).

Spot metering is where the meter measures a specific spot only - it doesn't take into account anything else in the frame. I use this quite a bit for flowers and macros - I can make sure that the part of the flower I want exposed properly isn't going to be blown out by the camera being confused by a black background. It's NOT good to use for something like soccer (I did that once accidentally). The players were wearing black shorts and it happened that one of the shots had the exposure point on the black when I pushed the shutter - the picture was very overexposed and the shorts were mid-grey.

I'm not a technical person, but the way I understand it is that a circular polarizer works much like a venetian blind. A scene is made up of all kinds of light, some direct from a light source and some reflected from objects in the scene. A polarizer allows light to come in from only one direction, so it cuts out much reflected light from things like water etc. Because of this, colors often look more saturated. It also cuts down the amount of light getting through to the lens (like a pair of sunglasses) so you can use longer shutter speeds in bright light. They work well for smoothing out waterfalls and cutting down on the reflected light from the water. It's best if you are at right angles to the sun (a friend always said to have the sun off your shoulder) if you want the darkened skies/extra saturation, and are more effective at higher elevations.
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Old Dec 25, 2008, 9:32 PM   #4
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thank you so much for the explanation.
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