6d/T4i telephoto zoom

[chief]

Why is there a difference in closeness of image taken with a 6d and T4i using the EF 70-300mm f/4-5.6 IS USM lens? When zoomed out to 300mm object is a lot closer on the T4i image than the 6d. All settings on each camera are identical. I am confused. 

[kvbarkley]

The 6D is "full frame" the sensor is the size of 35 mm film. The T4i's sensor is the size of an APS-C frame, or 1.6X smaller, so the focal length of any lens will appear 1.6X longer.

[ScottyP]

The lens casts a circular image onto the camera sensor.  The image circle is made to be the right size to fit the large full frame sensors like that of the 6D.  

When you put a full frame lens on the smaller crop sensor camera like a Rebel T4i, a lot of the image circle spills out over the edges of the smaller sensor.  In effect, then, the sensor is cropping the image as it is being made, as only the center of the image is on the sensor.  The edges of the image circle fall outside the smaller sensor so they are not captured.

The result is just like you took a photo and then in post processing you cropped away the outside of the photo and then blew up the image to fill your monitor screen.  It looks like you zoomed in with a zoom lens.

[Waddizzle]