Partial metering with long lens = spot metering?

[gmax]

Hello,
I've moved my question here from the previous thread (started by magpiemick):
Something seems to keep me confused about this subject. :smoke:
This is what I grasped (quote):

"When a 20D camera is used with an 86mm lens, then, the spot angle (acceptance) is decreased from 11° (degrees) with a 31mm lens to about 4° (degrees) ... it is decreased to 1° (degree) with a 344mm lens .."

Does this mean that when choosing partial metering with my 560mm lens I'm actually using something close to spot metering?
So what's the difference with a, say, 30D spot metering? Why then someone using a long lens on a 30D should switch to spot metering?

Still confused |:S| , thanks for any clarification

Max

[Tannin]

I think it just means that with a telephoto lens you are looking at a narrower angle of view. (Like .. er ... duh.) Unless there is something subtle there on that website I clean missed, all he is doing there is saying that a lens with a narrower field of view has a narrower field of view than the field of view a lens with a wider field of view has.

The normal way to measure the "spotness" of a spot meter is as a percentage of the field of view. Measuring it as an angle ..... er ... why would you bother? What's the point?

Short answer: that quote was just an obscure and very complicated way of explaining something you already knew. Forget about it.

[mjmw]

I think it just means that with a telephoto lens you are looking at a narrower angle of view. (Like .. er ... duh.) Unless there is something subtle there on that website I clean missed, all he is doing there is saying that a lens with a narrower field of view has a narrower field of view than the field of view a lens with a wider field of view has.

The normal way to measure the "spotness" of a spot meter is as a percentage of the field of view. Measuring it as an angle ..... er ... why would you bother? What's the point?

Short answer: that quote was just an obscure and very complicated way of explaining something you already knew. Forget about it.

I agree - forget about it! As Tanin says, it is the percentage of the view in the viewfinder that is important - i.e. partial metering is still using the same area in the centre of the frame whether you have a 50mm lens or 500mm.

[gmax]

Thank you all ;)