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?
