Evaluative and partial metering.. please explain :(
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In broadest terms the different metering modes meter from different parts of your viewfinder.
Depending on what you are shooting and the prevailing lighting conditions, changing metering modes may give you a more accurate meter reading so that your pictures are correctly exposed.
Depending on what you are shooting and the prevailing lighting conditions, changing metering modes may give you a more accurate meter reading so that your pictures are correctly exposed.
OP
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So say you were shooting a person outside using flash.
And you wanted to underexpose the background by a stop and not use manual metering. You can use spot metering so it exposes for just the person and doesnt expose for the sky?
CT
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Evaluative metering.
Your focusing screen is divided into numerous little invisible portions rather like a honeycomb, and each portion is metered individually. The camera then analyses the scene and compares it with thousands of sample images stored on board to try to arrive at the ideal overall exposure for the scene based on all those readings. Nikon's system is very similar except they call it Matrix instead of Evaluative. Individual manufactures are very cagey about the information they release on these systems and the nature of the stored sample images, but that's the bare bones of it.
Evaluative, whilst it can be fooled by extreme lighting conditions, is pretty reliable in most circumstances.
Partial Metering
Just meters from one area of the screen, usually a zone around the centre of the screen (but larger than a spot metering area.)
This is useful when you want to meter for a particular tone in your shot, ignoring darker or brighter areas. A good example would be a head and shoulders portrait taken with a bright background such as the sky, where the partial zone would meter from the skin tones of the subject while ignoring the brighter background.
EDIT
Sorry I ddn't see you asked about spot metering.
True spot metering is best done with a good hand held meter, and the narrower the angle of the spot reading the better. Better hand held meters read a 1 degree spot angle for taking accurate readings from very small areas.
Spot meters in cameras read from a larger angle - usually around 6- 9 degrees, so still very useful for metering from a small tone in your scene when you're trying to decide the best overall exposure for the scene.The camera spot metering area is usually marked with a circle in the centre of the focusing screen.
To get the best from spot metering you really need to have a pretty good grasp of basic exposure principles or you can cause more problems with it than you solve. For example if you tried spot metering on a magpie, you have only two tones .....black and white, so you'd end up with gross over or under exposure depending on whether you metered on a white or black bit of the bird - It's a classic situation where an 18% grey reading would probably give the best result.
Your focusing screen is divided into numerous little invisible portions rather like a honeycomb, and each portion is metered individually. The camera then analyses the scene and compares it with thousands of sample images stored on board to try to arrive at the ideal overall exposure for the scene based on all those readings. Nikon's system is very similar except they call it Matrix instead of Evaluative. Individual manufactures are very cagey about the information they release on these systems and the nature of the stored sample images, but that's the bare bones of it.
Evaluative, whilst it can be fooled by extreme lighting conditions, is pretty reliable in most circumstances.
Partial Metering
Just meters from one area of the screen, usually a zone around the centre of the screen (but larger than a spot metering area.)
This is useful when you want to meter for a particular tone in your shot, ignoring darker or brighter areas. A good example would be a head and shoulders portrait taken with a bright background such as the sky, where the partial zone would meter from the skin tones of the subject while ignoring the brighter background.
EDIT
Sorry I ddn't see you asked about spot metering.
True spot metering is best done with a good hand held meter, and the narrower the angle of the spot reading the better. Better hand held meters read a 1 degree spot angle for taking accurate readings from very small areas.
Spot meters in cameras read from a larger angle - usually around 6- 9 degrees, so still very useful for metering from a small tone in your scene when you're trying to decide the best overall exposure for the scene.The camera spot metering area is usually marked with a circle in the centre of the focusing screen.
To get the best from spot metering you really need to have a pretty good grasp of basic exposure principles or you can cause more problems with it than you solve. For example if you tried spot metering on a magpie, you have only two tones .....black and white, so you'd end up with gross over or under exposure depending on whether you metered on a white or black bit of the bird - It's a classic situation where an 18% grey reading would probably give the best result.
CT
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LOL Glad it's helped and now I'm a legend in my own lunchtime! 
Yep. Partial metering should do what you want, although there's numerous ways to skin the rabbit. Regardless of what metering method you're using, if you move in close to your subject so that he/she fills the viewfinder, you can use manual mode and balance the exposure for the skin tones. Then move back to where you intend to take the shots from and as long as the light doesn't change you can retain those settings as long as you like.
Alternatively if you're using AV - still move in and meter from your subject then press the exposure lock button and move back. The disadvantage is you lose the settings after each shot, but it's very quick and effective for the odd shot.
You complicated the issue a bit with your flash question as it depends on whether you just want to just lift the skin tones and fill the shadows with fill flash or whether to want to try to balance the subject with the background, which is why I deffed it.
Yep. Partial metering should do what you want, although there's numerous ways to skin the rabbit. Regardless of what metering method you're using, if you move in close to your subject so that he/she fills the viewfinder, you can use manual mode and balance the exposure for the skin tones. Then move back to where you intend to take the shots from and as long as the light doesn't change you can retain those settings as long as you like.
Alternatively if you're using AV - still move in and meter from your subject then press the exposure lock button and move back. The disadvantage is you lose the settings after each shot, but it's very quick and effective for the odd shot.
You complicated the issue a bit with your flash question as it depends on whether you just want to just lift the skin tones and fill the shadows with fill flash or whether to want to try to balance the subject with the background, which is why I deffed it.
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Very helpfull mate, forever in your debt
tis very helpful - if you had read the manual you would know :bang:
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I wouldn't use spot for that, and as CT says it's really an application you should only use when you have a good understanding.
Basically in that situation I would put the camera on Av and say -1 on the camera's (not the flash's) exposure compensation. The camera will then set an ambient exposure that will under expose by one stop, and the flash will expose as normal.
You can adjust both ambient and flash exposures very easily in this way. Obviously using flash exposure compensation on the gun (or in the menu for the pop-up unit).
If you want to try this, get to know the flash exposure lock button FEL* and use it especially with off-centre subjects - handbook explains. Flash can be tricky because it's affected a lot by subject distance. The FEL feature will nail that for you.
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I thought the Basics forum was a place for folks that either don't know the answers, or for those that do know, and are willing to explain them :shrug:
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But there's people that are just starting out that are on a steep learning curve, and some questions like this, they will spot, and realise they have the feature to learn.
I explained in my OP why I posted the question on here.:razz:
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Just been out and tried exactly that.
Perfect. Thanks alot. Now I can use outdoor flash with much more confidence.
Hoppy 
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If it is anything like my D300 manual, not a lot to be honest, I have 400 + pages telling me what features it has, and what menu items it has, but at no point does it tell me when and how I should use those features.
The question was valid, and well answered by CT and Hoppy.
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Just been out and tried exactly that.
Perfect. Thanks alot. Now I can use outdoor flash with much more confidence.
Oh wicked! That's good
Dunno if you're using the pop-up or a separate gun, but it's even easier with a separate flash, because a) the flash exposure compensation is right in front of you on the back, and b) you'll probably have High Speed Sync as an option with most guns.
HSS is really cool for this sort of thing as it's quite common when shooting outdoors for the shutter speed to rise above the max x-sync speed. Even when you raise the f/number and reduce ISO, you can run out of options. HSS sorts that and, with most cameras, you can just leave HSS enabled and the flash will automatically switch over to it when the shutter speed demands it, and back off again when it doesn't.
With HSS it's easy to shoot with low-f/numbers for shallow DoF even on bright days.
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And if Trev hadn't asked the question on here then CT's & Hoppy's invaluable answers wouldn't be available for all to see. This is, after all, a discussion forum.
If you have nothing constructive to contribute to a thread would you please just keep out of it in future. Posts like yours only serve to antagonise.
STARRIDER
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Good description. I have read the manual many times and although I understand what the modes do I couldn't really work out why I would use any apart from Evaluative, or just switch to manual.
Thanks. And just ignore the non-helpful people in this thread. ;o)
Thanks. And just ignore the non-helpful people in this thread. ;o)
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Too bloody true.
Plus. There's ways that settings can be manipulated, to get the results that you want.
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Thank you. Exactly why I posted in the first place. I've got exactly what I came on here looking for, and I hope that others have learnt something too
Its the * button on the back of your camera.
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There are often various ways to lock settings or override them, but they sometimes re-set automatically after you've taken a shot etc.
The only way to lock everything permanently, is to switch to manual. In my opinion, 'manual' anything is better described as Set & Lock - manual shutter speed/aperture/ISO, manual focus, manual white balance, manual flash control and so on.
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hashcake
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I've just had a look at the manual and it states the following.
A pointless comment on a forum thread to provoke a response is typical of a troll