F 5,6

hark

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Staff member
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It sounds like you might have a variable aperture zoom lens--possibly one that is listed as f/4.5-5.6? For example, if it's a lens like the Nikon 70-300mm f/4.5-5.6, when the lens is set at 70mm, you will be able to shoot at f/4.5. However, when you start to zoom to a longer focal length, the aperture will automatically stop down. By the time you reach the end of the zoom range (300mm with this particular lens), the widest aperture you can use is f/5.6.

Lenses with variable apertures are less expensive than lenses with fixed apertures. Nikon makes some zooms such as the 70-200mm f/4. With this lens, no matter where you zoom, you can shoot at f/4 if you wish. And they also make some zoom lenses that are f/2.8. Those are even more expensive than the zooms made with f/4.

So if you have a variable aperture zoom and you need and/or want to shoot at the lower f-stop, then you'd have to shoot at the low end of the zoom and crop your image to get a tighter view if you don't want to zoom and shoot at the longer focal length with a stopped down aperture.
 

pforsell

Senior Member
Please some help/
I have a new D5500..for some reason I can not open more than f 5,6
Any idea??
Thanks

Probably everything works as they should, but my guess is that the lens you are using is the limiting factor. For example, if you have the kit lens 18-55 mm f/3.5~f/5.6 that means the lens is capable to f/3.5 at the short end i.e. 18mm but in the long end at 55mm only f/5.6 is available.

A variable aperture zoom changes the maximum aperture at one-sixth of a stop intervals, for example the 18-55 I mentioned above has these maximum apertures:

* 18mm f/3.5
* 20mm f/3.8
* 24mm f/4
* 26mm f/4.2
* 33mm f/4.5
* 35mm f/4.8
* 39mm f/5
* 42mm f/5.3
* 48mm and beyond f5.6
(focal lengths are approximate, I read them from the lens barrel)

The most popular wide aperture lenses new users often buy are AF-S DX 35mm f/1.8G and AF-S 50mm f/1.8G and perhaps AF-S 85mm f/1.8G. Those are prime lenses (single focal length) but they have a pretty big maximum aperture of f/1.8 while at the same time being very affordable. The top-of-the line f/1.4 versions tend to command much higher prices, even several thousand dollars a piece.

If you prefer zooms, then Nikkor has for example the AF-S DX 17-55mm f/2.8 constant aperture zoom that opens up to f/2.8 at all zoom settings. It is a very solidly built full metal lens with very good optics, but that unfortunately means a little higher price tag too.
 
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