The differce between a full-frame sensor (36 x 24 mm) and an aps-c sensor (22.5 x 15 mm)

 

 

 

 

 

 

On the left you see a northern dune tiger beetle (Cicindela hybrida) photographed with the EOS 5D MkII, and on the right, the same image as it would look like if it was photographed with a camera with APS-C sensor.
It is often said that a smaller sensor increases the depth of field, and lens focal length. Neither claim is entirely correct, however.

The lens makes the image, and the lens does not change focal length when you mount it on a different camera. With a smaller sensor only a smaller part of the image is produced by the lens. Nothing more and nothing less.
Depth-of-field is determined by the lens aperture, in conjunction with the lens focal length and distance from the subject.
The apparent focal length increase (often called lens factor) and apparent increase in depth of field are therefore only present because you are looking at a smaller proportion of the total image.

Specifications:

Camera: EOS 5D MkII
Lens: Canon EF 180mm f/3.5L Macro lens USM
Aperture: f/22
Shutter speed: 1/200
Lighting: Flash-fill with the Macro Twin Lite MT-24E