I get no picture through the lens, only a white background.

Hi
take a look in the picture line in menu.
open Samsung MagicAngle put it on off. My background became much clearer when I put it off

Go to settings and change the lens exposure time or just set a focus point for the picture on a darker spot to change the white balance

Exposure meters are designed on the premise that the scene is an average, middle gray, in brightness. If you take a picture of a white dog playing in the snow, the camera will try to make the picture come out middle gray (a gray dog playing in gray snow). If you take a picture of a black cat sitting on black asphalt, the camera will try to make the picture come out middle gray (a gray cat sitting on gray ground).

If the white background is dominating the scene, the camera will reduce exposure to try to make the entire scene come out middle gray. The solution is to meter on something else. Move in close and fill the frame with the subject, press the AE-LOCK button, then move back, compose the picture, and take the shot. For full details, refer to the "Shooting with the exposure locked --- AE-LOCK" section in the manual (page 52 in my copy).

If you're taking a lot of pictures, you might want to switch to Manual mode and set the exposure accordingly.

Are you saying that you're using a white background but it doesn't appear white in the pictures? If so, then yes, you need to change the white balance to match the light. Probably "tungsten" but you could try different settings and pick the one you like best or you could use a white piece of paper and set a manual white balance.

Hi!
Does the smudge changes / mooves as you zoom the lens? If so, the smudge is most likely on the focus lens, if not, there's something on the CCD. In both cases the lens will have to be taken apart and cleaned by a professional. I suggest you contact a local repair shop and see how much they ask for it.

Tom

Do you know why your background black?Try to see in front of your lens. If you don't see move in your diafragma, it can be your lens trouble. Especially at the flexible wire.
But if you see diafragma moving when you zoom..I think you have ccd problem.

this is, in most cases, a desired effect (bokeh) which is used to "detach" the subject from the background avoiding the viewer of the picture to be distracted by the background. This technique is widely used in portraits. This effect effect will be more pronounced when the lens is wide open (in your case it should be f/3.5 if I remember well...). To practice you may try the following: set you camera to "A" mode and take one picture of something (it should not be a landscape) using the smallest aperture after this take the same pic using the biggest aperture. With the lower f number you should get a blurry background and with the biggest the backgroud should be in focus!

EOS 400D / Rebel XTi Digital Camera
EOS 400D/Rebel XTi doesn't have live view function, so you cannot see the picture you are taking.

take the lens out and blow air inside the camera and on the inside part of the lens.

This camera does not have the facility to take "black & white" photos. However it is easy to convert the colour pictures to black & white using software once they are on your PC. Here is a great FREE utility that will do what you need: http://perso.orange.fr/pierre.g/xnview/enxnview.html If you need any help with it let us know. Please update the question & let us know if the information given was useful to you - Good Luck!