EF lenses have an image circle large enough to cover the full- frame format of film and some digital models. A range of EF lenses was introduced at the same time and the number has increased over the years. When Canon introduced the EOS camera system back in 1987 it featured a new lens mount – the EF mount (short for ‘electro-focus’). This is much more useful than knowing the crop factor. These are the benchmarks for identifying lens types.Ī focal length greater than the standard is telephoto and a focal length less than the standard is wide-angle. On an APS-C camera it is around 27mm (43mm divided by 1.6). On a full-frame camera this is 43mm – and so typically a 50mm is regarded as a standard lens for full-frame purposes. Our advice? Forget about crop factors! And extended reach, too!Ī standard focal length for a camera is usually taken as the diagonal of the image frame. But that is not a common situation for most of us, so it is best just to get used to the view given by a lens on your camera. So essentially this means that if you have a full-frame and an APS-C camera side by side, you need a longer focal length lens on the full-frame camera to see the same view as the APS-C camera. Similarly, the full frame sensor is 1.3x larger than the APS-H sensor.) The maths… We multiply because the full-frame sensor is 1.6 times bigger than the APS-C sized sensor. The rest of the image falls outside the area of the APS-C sensor.įACT: All lenses produce circular images, but the sensor (or film negative) only collects the data that falls onto its rectangular surface area.Ī crop factor of 1.6x – often talked about with APS-C cameras – can be explained like this: If you are using a 50mm lens on an APS-C camera and you want to shoot the same scene with the same field-of-view with a full-frame camera you need a focal length of 50 x 1.6, which is 80mm. There is no change to the image created by the lens – it’s simply that the smaller sensor only captures the central area of the image. You could get an identical result by enlarging and cropping the full-frame image. It is a magnification effect, not a change of focal length. In fact, the APS-C image has been enlarged more than the full-frame image to match the display size. The result from the APS-C sensor is shown above and appears to show an increased telephoto effect. When you come to display an image to fill a computer screen or a print, the result from the full-frame sensor is shown above. The field-of-view is narrower, but nothing else changes. The end result is a smaller area captured, but exactly the same as the central area of the full frame image. An APS-C camera only records a part of the full image (as shown by the white box on the central image). A full-frame camera captures the full image. The original shot was taken with an EF 400mm lens. The focal length might not change, but what does change is the field-of-view. Use the same lens on a full frame camera and an APS-C camera, and you end up with results like those below. It doesn’t.įACT: Focal length is a characteristic of the lens and is not affected by the camera or sensor size. There is a lot of confusion about crop factors, extended reach and telephoto effects when using lenses on APS-C cameras.įirst, let’s dispel the myth that the focal length of a lens changes when switched between a full-frame camera and an APS-C camera. So what does this all mean for your photography? Crop refers to the fact that the image you get with the smaller sensor is a cropped part of the image obtained with the full frame sensor. The main reason for the introduction of the smaller sensor was cost – full frame sensors are expensive. Then, in 2000, along came a camera with an APS-C 'crop' sensor – the EOS D30. EF lenses, like the FD lens system that went before, gave full coverage to 35mm EOS film cameras, then subsequently full-frame – 36 x 24mm sensor – digital cameras. The EF lens mount was introduced in the same year that the EOS was announced – 1987. Terms like ‘crop factor’, 'extra reach’ and ‘equivalent focal length’ just aren’t helpful. This is exactly what happened – as far as we’re concerned – when Canon introduced the EF-S lens mount. Sometimes when an attempt is made to simplify or explain a term or reference point, it can end up complicating the situation.
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