![]() ![]() (They are usually lower quality, however, and can introduce vignetting and other artifacts. The f-stop is calculated by dividing the focal length of a lens in. Most camera lenses offer a range of f-stops (from. To focus on something closer than infinity, the lens is moved farther away from the film. Technically, f-stop is the ratio of the lens focal length to the diameter of the aperture. The f-stop is the number a camera (or lens) displays to indicate the size of the lens aperture (see 'F-stop vs aperture' below). Note that teleside converters and wide-angle converters which go on the front of the lens do change the effective aperture (see What's the difference between real and effective aperture?), so they don't change the f number. In other words, focal length equals image distance for a far subject. When you set the aperture on the camera to f/5.6, the aperture on the lens is set to the same position that would be f/2.8 without the extender (but which genuinely is f/5.6 with it). ![]() This explains the part you were confused about: the camera is aware of the change already and the numbers it is showing you are what you will actually get. ![]() Are F-stop and Aperture the Same Thing F-stop stands for the aperture. It refers to the aperture setting, the command that controls the size of the opening that allows light into the camera. This is the case with the Canon extender you have, but might not be with third-party ones. The F-stop is part of the three components that make up the exposure triangle in photography. Some converters communicate intelligently with the camera body, so the aperture displayed will be correct. (See How can a speedbooster improve the light performance of a lens? for more.) Here’s an example: Nikon AF-S FX NIKKOR 200 500mm (7.9 19. So, you have to try 1/2 or 1/3 stops as you reduce the aperture from the maximum. However, some telephoto lenses and cameras may need a setting other than a full f-stop. This is also why rear wide-angle converters can go the other way, effectively increasing the aperture. We all know that F-Stop represents the aperture setting on the lens, and ultimately controls how much light is hitting the sensor. Generally, an appropriate setting is 1 to 2 f-stops from the maximum aperture. (If this is unclear to you, see the bit about f numbers in this other answer.) That means that the relative size of the aperture decreases, so the f number does in fact actually change. The additional element changes the focal length of the lens, without changing the apparent size of the aperture. This is really simple when you think about it. ![]()
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