Nikon 18-55 f:3.5/5.6Camera error: no lens fitted or non-CPU lens

Turn the aperture ring on the lens to its smallest setting (largest f/number) and then forget it's there. You can control the aperture from the camera body, the same way as on lenses without an aperture ring.

Turn the aperture ring to its smallest setting (largest f/number). Control the aperture from the camera, the same way you do so on a lens without an aperture ring.

This is usually a lens issue. If the lens is not properly attached or the lens is a non-cpu lens it shows this error. If you are using an older non-cpu, you have to switch to M-mode to use it.

Hi mmarushack, in the manual page 132 it states that the F- - error means the lens is not attached or a non CPU lens is attached. If a older non CPU lens is attached select M mode. That would be on the right side of the lens mount as you face the front of the camera. The assumption is you have a CPU lens then I would suggest doing a reset of the camera. Open the terminal rubber flap on the left side of the camera. Just below the USB connector is a small push button. That resets the camera thus fixes you camera. If not do call Nikon at 800-645-6689

I'm assuming this lens worked on another Nikon camera before and that the lens mount is for Nikon cameras. Make sure the aperture ring is set to "A". Clean the contacts on the lens and camera body where they meet with a cotton swab lightly dampened with rubbing alcohol.

First, if you can try the lens on another camera body, please do. See if the same thing happens on a different camera body. If it does, it's a problem with the lens. If not, you need to look at the camera. You can verify it's the camera by placing a different lens onto the body and see if you're experiencing the same problem. If it is indeed the body, I would suggest you take a pencil eraser and gently but firmly clean the contacts located on the lens mount. It's my experience (I also shoot with a D200) that often times when a lens isn't autofocusing, it's due to direty contacts either on the lens itself or the camera body. Cleaning them is a good start though and will narrow your issues down to the lens or the camera body. After cleaning, try the lens again to see if it's working correctly. If not, send it to Nikon in New York for repairs.

You have named several excellent digital SLR cameras aimed at the top end of the amateur/semi professional market.
I have the Nikon D200 and have been very pleased with it.
As stated by JCDill, you must really decide what you want and can afford. The camera body you choose will commit you down one path or another. For example, if you choose Canon, only Canon or OEM (Other Equipment Manufacturers) such as Sigma lenses will fit your camera body. Canon have a good reputation for their auto-focus, while Nikon make lenses that are the envy of others.
If this is your first digital SLR then you might be best buying an entry level body with a multi-purpose zoom lens such as the Nikon D40. There is a lot to learn.
If you are converting from film SLR and already have a set of lenses, then the cameras you mentioned will probably be able to use your existing lenses (but this is less so with Canon than Nikon). I was ecstatic to disover that my old Nikon 500mm mirror lens works in manual mode (with metering displayed) on my Nikon D200 but would not work properly on my Nikon D70.
I hope this helps.

Does the camera body has a M/AFswitch? it would be located in front on the left side if that accidently gets changed to M your lens will not AF any more until you change it?? I know it sounds so simple but who knows!! Barry Brown
www.coralreefphotos.com

Go to NikonUSA;.com, click on "Service & Support"; select "Product Registration".

Sigma lenses sometimes need re-chipping for full compatability with certain Nikon camera. They are usually quite good about doing this gratis.
Try the Sigma on another body at the camera shop or at home (preferably and older AF film camera). If it works then its likely just a chip compatibility issue.