Sensor size
Understand the difference the dimensions of your camera’s sensor makes
Although the lens determines the magnification of the subject, the subject will appear larger in an image taken on an EOS camera which has an APS-C sensor, compared with one taken on a full-frame camera. The magnification hasn’t really changed, it’s simply that the smaller sensor crops the full image projected by the lens. You can achieve the same effect by simply cropping a full-frame image in software, although you will lose some of the resolution when you do this.
Several full-frame EOS cameras allow you to crop the image in-camera. Both the EOS 5DS and 5DS R allow you to manually select smaller x1.3 or x1.6 crops when shooting JPEGS, for example. Cameras in the EOS R mirrorless range offer a manually selectable x1.6 JPEG crop, and will automatically switch to the smaller format when an Aps-c-friendly EF-S lens is attached to the camera via one of Canon’s R-series mount adapters.
There is an affordable way to achieve even greater magnification when you take a picture: add an extension tube. These hollow metal tubes fit between the camera and the lens and allow the lens to be focused closer than normal. They can also be stacked to give even greater magnification, although there is a trade off in terms of handling and light; an extension tube increases the effective aperture – you’ll need to use a longer shutter speed or a higher ISO, or increase the power of the flash or other light source to compensate for the loss of light.