The actual focal length of a lens on an APS-C camera is exactly 1 what is written on the lens. What you're probably confused about is the fact that the field of view you get from mounting a 50mm lens on an APS-C camera is the same is that of mounting a 75-80mm lens on a full-frame camera (this varies a bit because "APS-C" sized sensors vary a
The resulting photos captured using the same focal length on full-frame (red), an APS-C sensor with a 1.5x crop (blue), and a Four Thirds sensor with a 2.0x crop (green). The focal length and field of view is the same for EF and EF-S lenses on the same camera. however, when reading a lens review that was made on a FF camera, note that the overall experience of that lens on a crop camera may be different (for example, I love the 70-200 on full frame, but rarely use it on my 7D as it gets "quite long" on that camera).
So, a 17mm lens used on such a camera will provide an effective focal length similar to a 34mm lens on a full-frame body. Similarly, a 12-35mm lens provides a focal range equivalent to 24-70mm
APS-C and full-frame: 2 different-sized image sensors 2. Consideration #1: Impact on camera and lens sizes 3. Consideration #2: Low light and high ISO performance 4. Consideration #3: 1.6x crop factor 5. Consideration #4: Depth of field 6. In conclusion: APS-C or full-frame camera? APS-C and full-frame: 2 different-sized image sensors Full-frame has shallower DOF when comparing equivalent focal length, or in other words lenses that produce the same field of view on the different sensor. This means APS-C will have a shorter focal length, which results in wider DOF. APS-C will also have wider DOF when comparing shooting with the same focal length and achieving the same framing. ogOKH. 38572564270652627580997
