Bill Pierce
Well-known
If you use a small, non reflex camera with Live View focusing, how do you focus?
Phase detect autofocus, normally associated with big DSLR’s, is FAST. (But, because, it is checking the focus on, not the sensor that records the image, but a separate sensor, it can be inaccurate. The problem is solved when cameras bodies using phase detect allow you to set up autofocus corrections for each individual lens.)
Because focus in Live View in the little cameras is read off the imaging sensor, it can be quite accurate. The problem is that it’s SLOW. Here’s a quote from Wikipedia.
“In this method, AF does not involve actual distance measurement at all and is generally slower than phase detection systems, especially when operating under dim light. Furthermore, as the autofocus system does not calculate whether the subject is in front focus or back focus, focus tracking is not feasible. As it does not use a separate sensor, however, contrast-detect autofocus can be more flexible (as it is implemented in software) and potentially more accurate.”
In other words, phase is fast and live is accurate. (Fuji, Ricoh, Nikon, Canon and probably some others I don’t know of have worked out systems in more recent cameras where, more or less, phase rough focuses and live fine focuses.) If you use a little camera with only Live View focusing how do you deal with the problem of slow focus? As an old rangefinder photographer used to manual focus, my answer is simple. I prefocus. It doesn’t matter if its manual, phase or live view. Focusing, along with setting exposure, are something I do before I start shooting. Obviously, in a few situations, this can be a disaster. But in most situations it means less time between seeing the moment and recording the moment.
Again, when you use a camera with Live View focusing, how do you deal with the problem of slow focus (unless you do landscapes or still lifes)?
Phase detect autofocus, normally associated with big DSLR’s, is FAST. (But, because, it is checking the focus on, not the sensor that records the image, but a separate sensor, it can be inaccurate. The problem is solved when cameras bodies using phase detect allow you to set up autofocus corrections for each individual lens.)
Because focus in Live View in the little cameras is read off the imaging sensor, it can be quite accurate. The problem is that it’s SLOW. Here’s a quote from Wikipedia.
“In this method, AF does not involve actual distance measurement at all and is generally slower than phase detection systems, especially when operating under dim light. Furthermore, as the autofocus system does not calculate whether the subject is in front focus or back focus, focus tracking is not feasible. As it does not use a separate sensor, however, contrast-detect autofocus can be more flexible (as it is implemented in software) and potentially more accurate.”
In other words, phase is fast and live is accurate. (Fuji, Ricoh, Nikon, Canon and probably some others I don’t know of have worked out systems in more recent cameras where, more or less, phase rough focuses and live fine focuses.) If you use a little camera with only Live View focusing how do you deal with the problem of slow focus? As an old rangefinder photographer used to manual focus, my answer is simple. I prefocus. It doesn’t matter if its manual, phase or live view. Focusing, along with setting exposure, are something I do before I start shooting. Obviously, in a few situations, this can be a disaster. But in most situations it means less time between seeing the moment and recording the moment.
Again, when you use a camera with Live View focusing, how do you deal with the problem of slow focus (unless you do landscapes or still lifes)?
