newbie question about exposure

[tony99]

hi,

i'm new to photography, but I have questions about aperture, shutter speed , f-stop, and spot metering.

I know aperture is the opening that lets light pass and smaller the aperture bigger the light pass the lower the depth field.

shutter speed basically how quickly a picture is taken.

I also know that both aperture and shutter speed makes exposure. But where I am very confused is the f-stop and spot metering

f-stop has to do with aperture and zoom but i really don't know.

also in my SLR I have a spot metering and I was reading it has to do with tone. i.e people wanting to take sunset photo take spot metering of a sky the move to the sun to take the picutre.

my really question is what is f-stop and spot-metering and how do they affect exposure?

thank you.

 

[ksmattfish]

f/stop is how aperture size is noted. It's not just about how big the hole is, it's how big is it in comparison to lens focal length.

F/# = lens focal length divided by actual aperture size.

So if you have a 28-200 zoom lens set at 200mm, and the aperture size is 50mm, then the f/stop is f/4 (200/50=4). If the lens is at 28mm, and the aperture is 7mm wide, then the aperture is also f/4 (28/7=4).

A spot meter works the same way as any reflected light meter, it just is able to measure a smaller area of the scene. It is used to check light levels in specific areas of the scene.

You probably have matrix, center weighted, and spot metering in your camera. Matrix metering meters the entire scene, but it gives more importance to certain parts (such as the center). Center weighted meters what is in the center of the view screen. Spot meter does the same, but it measures a smaller area.