Bill Pierce
Well-known
I was wondering what focusing system folks prefer for fast focusing.
There are two basic forms of autofocus. Phase detection, found in many DSLR’s, is incredibly complex in its operation but fast, so fast it can track a moving object. However, it is usually not dealing with the actual image on the sensor plane. This can lead to manufacturing tolerance problems between lens and body, even problems with expansion or contraction in hot or cold weather.
Contrast assessment or Live View usually deals with the image on the actual sensor. The in-focus image has the highest contrast. The camera shifts focus and searches for that high contrast image. It’s slow, and it requires an area of good contrast in the picture. But it’s simple and usually accurate because it is normally using the sensor itself to determine focus.
Canon, Fuji, Nikon, Olympus, Samsung and Sony use a hybrid system on a few of their cameras, essentially using phase detection to achieve a fast focus and contrast detection to fine tune it.
That said, focusing, reframing and shooting, and doing this prior to every time you push the shutter button, is slow regardless of what autofocus system you use. Still, this is what I see many photographers doing with autofocus cameras, especially if they have never used a manual focusing camera. The easiest way to minimize the time between pressing the shutter button, having the camera focus and having the shutter go off is to eliminate focusing. That is to say, pre focus. Focus and then lock the focus down. Now start thinking about taking a picture. With the focus locked, shoot until the subject moves enough that you have to refocus. Don’t waste time or lose your concentration on the subject by refocusing until you have to.
A confession… Because hitting the auto focus lock button is one more button to push, I sometimes forget and end up refocusing with every “frame.” And then I feel stupid. Any thoughts?
There are two basic forms of autofocus. Phase detection, found in many DSLR’s, is incredibly complex in its operation but fast, so fast it can track a moving object. However, it is usually not dealing with the actual image on the sensor plane. This can lead to manufacturing tolerance problems between lens and body, even problems with expansion or contraction in hot or cold weather.
Contrast assessment or Live View usually deals with the image on the actual sensor. The in-focus image has the highest contrast. The camera shifts focus and searches for that high contrast image. It’s slow, and it requires an area of good contrast in the picture. But it’s simple and usually accurate because it is normally using the sensor itself to determine focus.
Canon, Fuji, Nikon, Olympus, Samsung and Sony use a hybrid system on a few of their cameras, essentially using phase detection to achieve a fast focus and contrast detection to fine tune it.
That said, focusing, reframing and shooting, and doing this prior to every time you push the shutter button, is slow regardless of what autofocus system you use. Still, this is what I see many photographers doing with autofocus cameras, especially if they have never used a manual focusing camera. The easiest way to minimize the time between pressing the shutter button, having the camera focus and having the shutter go off is to eliminate focusing. That is to say, pre focus. Focus and then lock the focus down. Now start thinking about taking a picture. With the focus locked, shoot until the subject moves enough that you have to refocus. Don’t waste time or lose your concentration on the subject by refocusing until you have to.
A confession… Because hitting the auto focus lock button is one more button to push, I sometimes forget and end up refocusing with every “frame.” And then I feel stupid. Any thoughts?
willie_901
Veteran
Phase detection is best for action photography.
Contrast detection is not susceptible to mechanical mis-calibrations.
Now that CPU performance for non-DSLR cameras has progressed past the level required for typical P&S, consumer, small sensor (high DOF by default) usage, PD AF performance is improving. Gradual adoption of fast AF motor technologies and mechanical strategies is slowly improving AF performance as well.
I use cameras with hybrid sytems. For fast focusing I use the PD AF manually much as I used optical RF film cameras (focus and recompose).
Otherwise, In my view, the photographer benefits from being willing to change AF techniques to match the circumstances at the time. This requires understanding how the different AF modes work and developing the experience to use the best AF techniques as needed. For instance, CD AF techniques in low light (EV 4-6) and when focus subjects have low contrast requires significant practice and experience. When I used an excellent DSLR PD system, one mis-set AF menu parameter would ruin otherwise spectacular action photography AF performance.
I am not interested in action photography. But if I was DSLR PD systems are still the best choice right now.
Contrast detection is not susceptible to mechanical mis-calibrations.
Now that CPU performance for non-DSLR cameras has progressed past the level required for typical P&S, consumer, small sensor (high DOF by default) usage, PD AF performance is improving. Gradual adoption of fast AF motor technologies and mechanical strategies is slowly improving AF performance as well.
I use cameras with hybrid sytems. For fast focusing I use the PD AF manually much as I used optical RF film cameras (focus and recompose).
Otherwise, In my view, the photographer benefits from being willing to change AF techniques to match the circumstances at the time. This requires understanding how the different AF modes work and developing the experience to use the best AF techniques as needed. For instance, CD AF techniques in low light (EV 4-6) and when focus subjects have low contrast requires significant practice and experience. When I used an excellent DSLR PD system, one mis-set AF menu parameter would ruin otherwise spectacular action photography AF performance.
I am not interested in action photography. But if I was DSLR PD systems are still the best choice right now.