All the photos in my camera looks like a fish eye or something, maybe I'm some configuration there, any help? this is how all the photos looks like:
Based on your comment, you have a Sigma 17-70mm f/2.8-4 DC Macro OS HSM Lens, which is an APS-C lens, on a full-frame camera. An APS-C sensor is smaller than a full-frame sensor, so the lenses that are designed for these cameras project a smaller image circle. APS-C specific lenses aren't designed to be used with with full-frame cameras. (See this post for a bit more detail about sensor sizes.)
Canon's APS-C specific lenses (with EF-S in the model number instead of EF) have a different mounting flange to prevent you from mounting them on full-frame cameras such as your 6D, but pretty much all third party APS-C lenses in the EF mount will mount on Canon FF cameras.
Lenses' product descriptions usually (ideally always) state pretty prominently whether they're for crop-sensor or full-frame cameras, so you can use this information to help you determine whether a lens is suitable for your camera. If the description of a lens states that it's for APS-C, crop-senor, or digital-only, then this is an APS-C specific lens, and isn't designed for your camera. If it states full-frame, then it is (see note 1 below).
Here's some information from Michael C's answer to this question and from a community wiki about decoding lens model numbers that should help steer you to the right types of lenses in the future:
Look for this
- Sigma lenses: Model numbers containing the designator DG (not DC)
- Canon lenses: Model numbers that begin with EF (not EF-S or EF-M)
- Tamron lenses: Model numbers that contain the designator Di (not Di II or Di III)
- Tokina lenses: Model numbers that contain the designator FX (not DX)
- Samyang lenses: Model numbers that do not contain the designator CS
When you're shopping on a site like B&H Photo, you can use the filter function to only display lenses that are designed for your full-frame camera:
Note 1: You might encounter a product description for a full-frame lens that talks about the lens's effective or equivalent focal length on a crop sensor camera. This is because the reverse of your situation—using a full-frame lens on a crop-sensor camera—is perfectly okay, and fairly common.
So now what?
Based on the fact that you linked to B&H in your comment, I'll assume you purchased your lens from B&H Photo. They have a pretty good return policy, so you may be able to return this lens and use the credit toward a full-frame lens. If you bought both your lens and your camera from there, then hopefully they'll be understanding
If you're not able to return the lens for some reason, you could still get some use out of it, since it seems to at least function correctly on your camera.
- You could shoot photos with it and then use software such as Photoshop, GIMP, etc. to crop out the unexposed portions of the photos. In effect you'd be making a crop-sensor camera out of your full-frame camera. You'll lose some image size in this process, but it's not a total loss.
- You could use this as an artistic effect, and make photos where the circular view is part of the art.
- Use it to take pictures of crop circles. How meta.
You are apparently using a Sigma DC lens on the full frame Canon EOS 6D.
Sigma DC lenses are designed to be used on "crop body" cameras. That is, cameras with APS-C or smaller sensors. APS-C sensors are 24x16mm or smaller. SIgma DC lenses only need project an image circle large enough to cover an area 24x16mm with a diagonal measurement of just under 29mm.
The Sensor of your Canon EOS 6D is 36x24mm with a diagonal of just over 43mm. Thus, the image circle cast by your Sigma DC lens is not large enough to cover the 36x24mm sensor in your camera.
For Sigma lenses to use with full frame cameras, look for DG in the Sigma lens name.