I have a nikon d5000?

But when i try to make my aperture smaller its stops at 5… That can't be the lowest aperture help me please… I'm a beginner at this!

Aperture is dictated by the lens, not body
& you don't indicate the lens you are using

Assuming you are using the kit 18-55mm 1:3.5-5.6 lens, let's explain something. The "1:3.5-5.6" tells you the maximum aperture (lowest number) the lens will go at the focal length extremes, "18mm and 55mm". IOW, the maximum at 18mm is f/3.5 and the maximum at 55mm is f/5.6.So if it is stopping at f/5.0 then you must be zoomed at something close to 55mm.

Here are some sites that you can learn more about photography.
http://www.cambridgeincolour.com/...olour.com/
http://creativelive.com/courses/ - I recommend the "Fundamentals of Digital Photography"
http://www.geofflawrence.com/photography_tutorials.htm
http://www.nikonusa.com/...raphy.page

Hi! I have a Pentax K-x in Stormtrooper White!

At 55mm, the maximum aperture of your kit lens is f/5. That is so true.

What kind of lens are you using.

Kitlenses, those that come in the kit, are relative cheap, decent glass but certainly not "fast"

"fast" glass if when apertures go as wide as 2.8 or even better 1.8. 1.2. 1.0. Hell there's even some glass doing 0.95. How? I don't know!

Point is more expensive glass tends to retain a wider hole for light to go through. The Iris doesn't makes the hole smaller as you zoom in.

Your lens probably is the kitlens and well those to make them cheap have as negative that as you zoom in the amount of light coming through gets less. So yes F5 is very possible the widest for a zoom at a certain zoomed position.

That is why kitlenses are fine for beginning out but once you want more [think better control over the exposure] then you buy a lens with a fixed aperture width. Or one that goes from F2.8 to F4 orso.

Hell the kitlens being at widest F3.5 doesn't even allows for the quickest focussing the DSLR can offer.

Now it sounds like allot of money but trust me it is worth it. The Tamron 17-50mm Sp has a F2.8 over the full range. It might not be the sharpest over the full F2.8 range so you tend to use it from F4 but the point is. That you can zoom out and in and the exposure ingredient, the light in this case, stays the same. So the rest can stay the same to. Expensive? Not if you put in mind that equal lenses [well better build quality the least] can cost around 3x as much.

And once you begin to learn more and want more control it is very nice if your lens is not forcing you to change settings to adjust for the different widest apertures during the zoom range.