I get a shadow when i use my flash, at the bottom of my picture. i'm using a nikkor 18-200mm 1:3.5-5.6 g ed len with the built in flash

The Nikon Lens 18-55 wide angel inner lens loosens locks lens no picture

Try cleaning the contacts on the lens with a cotton swab lightly dampened with rubbing alcohol.

Are you using a lens hood? That could create the shadow.

Are these pictures taken using the built-in flash and with the hood on the lens? If so, you're seeing the shadow of the lens hood.

Remove the lens hood when using the built-in flash.

Check if the lens is properly mounted. If still you get the error message, clean the electrical contacts between the lens and the camera using an eraser. Take care not to let any dust fall into the body. Attach the lens and try.

From the Fuji S1 Manual:

F-- (Flashing) or (lit in M Mode)

Cause:
The lens mounted is not a Nikkor lens with built-in CPU or no lens is mounted on the camera.

Solution:
Use a Nikkor lens with built-in CPU (excluding IX Nikkor lenes). (Note that pictures can still be taken in M mode.)

Look carefully at your images taken with flash... on the horizontal image is the lower part of the image slighty darker and have a rounded fall off at the edges? Is the vertical image dark side a straight hard line or is there a rounding to the top and bottom?

What we are looking at is if you have a very wide angle lens with the lens shade attached to the lens, then the built-in flash catches part of the lens shade and make a shadow on your subject... take the lens shade off and try the same shot and see if that makes a difference...

Have a great day...

Ed

sir, replace ur image sensor,

The camera has a main mirror that you see with the lens off and a sub-mirror underneath the main one. It may be the sub-mirror is not flipping up completely when you take a picture. It could be off its hinges or damaged. Any good camera repairman in your area should be able to confirm this

The built-in Speedlight on many Nikon cameras is designed to be a convenient way to either light up a dark subject or to add fill light to a daytime scene. The built-in Speedlight cannot replace a full size, external speedlight which should be used when more power or coverage are needed. Because the built-in Speedlight is compact and close to the camera it cannot be used under all conditions. When using a lens that is physically very long, a subject that is very close, or a wide lens hood it is possible that a shadow may be cast upon the subject. Notice, in the sample below, the round shadow in the bottom center of the photo. When the lens is too long or the coverage is too wide with a close subject a shadow of the lens itself is cast. In figure "A" below the lens is casting a shadow. Switching (or zooming) to a shorter lens (figure "B") prevents the shadow and allows even illumination. If your lens, subject, or lens hood choice create a shadow, an external flash (either on the camera's hot-shoe or connected to the camera by a wire or wirelessly) should be used to fully light the subject.