Giving Cameras The Best Autofocus Possible, Autofocus From The Human Eye

[M II A II R II K]

Giving Cameras The Best Autofocus Possible, Autofocus From The Human Eye


By Christopher Mims

Read More: http://www.fastcompany.com/biomimicr...-the-human-eye

.....

For half a century, we've known that the human visual system has an exquisite ability to lock focus on an object instantaneously, a feat that no digital camera or camcorder has yet matched. Now, finally, scientists have developed a good guess about how we might do that, and have translated that method into software that could make its way into cameras that never lose focus. Johannes Burge, a postdoctoral fellow at the University of Texas, and his advisor Wilson Geisler, wondered how it was that the eyes of humans and many other animals were able to focus so much more efficiently than most digital cameras.

- In a traditional autofocus system, the camera uses only one piece of information about a scene to determine whether or not an object is in focus--its level of contrast. Contrast, says Burge, isn't always a perfect proxy for focus. But it's worse than that: To determine in which direction to re-focus, a camera must first change its point of focus and compare the new image it captures with the old one, to determine whether or not the object in question has a higher or lower level of contrast. Often, the camera isn't even re-focusing in the correct direction when it captures this second image. This method of "guessing and checking" is "slow and not particularly accurate," says Burge.

- Burge's and Geisler's approach is different. As they outlined in a recent paper in the Proceedings of the National Academy of Sciences, their software algorithm can analyze any still image captured from a scene and instantly know how to re-focus a lens to bring it into focus. It requires no before-and-after comparison. The way it works is that it takes an inventory of the features in a scene. Even though any two instants that a camera might capture are very different from one another, they tend to have a number of fundamental similarities. It's this built-in knowledge of what to expect--in essence, a statistical distillation of what the physical world looks like--that allows their algorithm to instantly know the degree and direction in which a scene is out of focus, yielding information about how much to change the focal length of a lens (biological or mechanical) in order to bring it into focus.

.....

[big T]

Poorly researched article. The "traditional autofocus system" they describe is called contrast detection autofocus, which is used in most compact point and shoot digital cameras and really is not traditional at all. DSLRs and, before them, autofocus film SLRs all use phase detection autofocus by necesity (no sensor on film cameras, or no image on the sensor as it is obscured by the mirror while composing on a DSLR). Not only is phase detection much faster, it does not suffer from the trial and error issue they describe, as the phase difference instantaneously tells the camera in which direction and by how much to move focus.

Of course AF still isn't perfect so if the researchers came up with a better solution then good for them (and us). But this article is garbage.

[diskojoe]

I want to check out the translucent mirror tech that sony has been using in its a series. I hear it works pretty nice compare to traditional sensor tech.

[Okayyou]

Yeah, the article seems to have been slapped together. Their solution requires the camera to be able to see the scene in order to process the information. If the scene is too dark wouldn't it have the same issue as current AF tech? Speed doesn't seem to be an issue with modern SLRs and fast focusing lenses. My camera, which has been out for 2 years uses contrast and color to focus. It will focus hunt in the deep dark but I've been impressed how often it is able to find focus. Live view is another story, focusing off the sensor feels like tech from the 1990s. I believe this is because the dedicated focus sensor doesn't receive any information when the mirror locks up. The camera is then using the main sensor to try and focus, I don't understand why this is a slower process. Maybe it's too much info for the non specialized main sensor to handle. I think Sony, Nikon and Canon are all moving towards having at least one model of mirror-less camera for video yet still functions as an SLR.