However, the 35mm film format is not, never has been, and never will be the "master" format against which all other formats are measured. The camera manufacturers have decided to use the 35mm film format as the reference format for DSLRs. That is to compare the field (angle) of view provided by a particular focal length on two different format cameras, one of which is considered the reference format for the comparison. The "crop factor" essentially has one purpose in life. Note that "Format" refers to the size of the film frame or digital sensor in a camera. The one thing to understand is that the focal length of a lens DOES NOT CHANGE when putting it on different format camera bodies. Please read this "sticky" covering the "crop factor". Thus, the maximum aperture of the 70-200 f/4 with a 1.4x extender mounted would be f/5.6. The maximum aperture becomes one stop smaller (higher f-stop number) with the 1.4x extender. If you add a 1.4x extender to the 70-200 f/4 lens, then the combination becomes a 98-280mm lens. A 70-200mm lens is, and always will be, a 70-200mm lens. Mike, the part I put in bold in the quote above is NOT correct. Now does that mean I can't shoot at f/4, or that I can but the amount of light coming in will be equivalent to what it is at f/6.3? Since I already have 1.6x crop factor, that makes the lens 112-320 already right? Now if I add either one of the teleconverters does it add onto the already stretched focal length? And what brand of teleconverters do you suggest? I would just go Canon, but I'm sure there's one that's just as good for a smaller amount of money.Īlso, if I used the 1.4x converter on this lens, it would make me one stop down to f/6.3. I was planning on getting either a 1.4x or 2x teleconverter later on for extra reach. I'm going to be picking up a Canon 70-200mm f/4 L(non IS)this week, and I have a 50D. Speedlite 420EZ | Speedlite 580EX | EF 1.4x II | EF 2x II In low-light situations, then it may hunt which will result in extra wear on the lens.
Taping the extra contacts on a 2x extender would allow you to autofocus even at f/8, but it will not always work. It will show a focal length of 200 and a aperture of 4, but in reality you will still have a focal length of 280 and an aperture of 5.6. If you tape the extra connectors on the extender, you may fool the camera. With the 1.4x extender, the camera will not allow you to select any aperture past 5.6. When you use a 1.4x extender, you will both multiply the focal length from 200 to 280 and at the same time multiply the possible aperture from 4 to 5.6. There is a mathematical relation between the focal length and the aperture. I'm not too sure, and I am going to wait until after I get the lens to see if I need the extra reach. So me losing one stop means the biggest aperture I can shoot with is f/5.6? As in the camera won't let me go lower, or that I can shoot at f/4 but it's as dark as f/5.6.
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