When zooming I want to keep background not blurred. Is this even possible? I will have multiple cameras pointing at one object from different distances can I get a flat picture on all of the cammeras without getting Dof if yes how?
Technically speaking, there's no such thing. With conventional cameras, there's only one distance that is in focus. Everything else is more or less blurred. The question is exactly how blurry is something not at the focus distance? That depends on many variables:
- The amount of blur one considers acceptable as "in focus." If the size of the blur is too small for our eyes to discriminate as blurry, we generally call that "acceptable."
- The aperture size used to take the photo
- The focal length used to take the photo
- The focus distance (the distance from the camera to the subject) used to take the photo
- How far the background is from the focus distance
- The size of the imaging medium (film or sensor)
- The display size of the final image (and the amount of enlargement needed to get from the film/sensor size to the display size
- The viewing distance of the final image
- The visual acuity of the viewer
All of these things rolled into one is what we refer to as "depth of field". We currently have 282 question here at Photography SE with the [depth-of-field] tag. I would suggest beginning with:
How can I take a photo with everything in focus with my DSLR?
What exactly determines depth of field?
What is aperture, and how does it affect my photographs?
What is "Hyperfocal Distance"?
How do I keep both the background and foreground in the image in focus at the same time?
How can a Frazier lens achieve that massive DOF?
If working with the shortest focal length, the smallest sensor (that's why mobile phones and cheap compacts can have enormous depth of field) and the smallest aperture (physical, not numerical! eg f/22. Beware of sensor dust!) doesn't yield enough depth of field, consider taking multiple shots at different focus settings and using so-called focus stacking software to edit them all into one. This requires a still subject and optimally the use of a tripod or similar camera attachment.