I had limited success using this mode as on quite a lot of images I missed the subject with this single point. Most of what I have read would suggest using just one central focus point and using the AI servo mode for this kind of work. I decided to try out some action photography to understand more fully the relationship of AI servo focus mode on Canon DSLR's. The course record was set in 1981 and still stands by J Wild in 15mins 53 seconds. The winning time this year 17min 18 second by number 169 Bob Hope. A gruelling run, distance: 5.2km / 3.2mĬlimb: 213m / 699 ft.
This rule for full f stops only requires that you can double, or half, a number.Įaster Saturday sees the annual Rivington Pike fell race. There is a way to calculate the 1/2 and 1/3 stop values however you can't do this in your head! Stops then 2 stops gives f8 (divide by 2) and 2 more gives f4 (again dividing by 2) ( or divide by 4 but half and half again might be easier for some) So for example if you are at an aperture value of f16 and want to open the aperture by 4 It's the same with the f1.4 two stops smaller is f2.8 (double the number), two stops smaller is So you can see how the sequence works.Įach step in the progression is 1 F stop, either bigger moving to the left or smaller moving to So begin with F1.0, two stops smaller is F2.0 (double the number), two more stops is F4 (double You only need to remember the F1.0 and F1.4 values. This gives a geometric scale of f1.0 f1.4 f2.0 f2.8
The F stops (full increment not 1/2 or 1/3 rd) are based upon a geometric incremented pattern based upon the powers of the square root of 2 If you are new to cameras (digital or film) and find the F stop notation difficult to understand, or remember, then this little explanation might help.
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