One of the most crippling features in many DSLR cameras (like the Canon Rebel T2i above) is the poor autofocus performance in both live view and video modes. While mirrorless cameras like the Panasonic GH1 and Samsung NX10 do a decent job of using contrast-detection AF methods, DSLR manufacturers like Canon and Nikon have done a poor job in making it work. Sony, to its credit, has implemented an effective live view design with fast autofocus by placing a secondary live view sensor in the viewfinder, which allows the standard phase difference AF sensor to function normally. But, still, it’s not a true “live view” of what the sensor will produce. Plus, Sony’s design won’t work with video.
Of course, most pros and serious amateurs understand the benefit and efficiency of using the fast, phase difference AF method that results from using the viewfinder. However, that doesn’t stop entry-level and enthusiast photographers from complaining about the poor live view and lack of video autofocus in their sub-$1000 DSLRs. Additionally, there are certainly situations where an accurate and quick live view or video autofocus mode are desired among photographers of all skill levels and backgrounds.
Canon may very well have the answer: Put the fast, phase difference AF sensors in pixels on the main image sensor.
A recently-published Canon patent application (USPTO App. No.12/664,529) demonstrates the use of phase difference AF sensors on individual pixels. While the patent primarily focuses (pardon the pun) on the pattern in which the “focus detection pixels” are placed on the sensor (specifically with regard to “thinning readout mode” for video capture), it appears to endorse the use of interpolation using adjacent image sensing information for the missing data resulting from a the “image sensing pixel” loss.
If Canon were to implement such a design, it could certainly change the performance of DSLR live view and video. However, it could also effect a number of other cameras – including point and shoot cameras, camcorders, and (perhaps) even a mirrorless camera with breakthrough AF performance.
Of course, nothing is for sure as to whether such a product will come to market in the near future. Still yet, it’s a little peek into the crystal ball at Canon HQ.
Sony had something similar patent a long time ago (phase detect AF on the main sensor), as does Nikon. It was never implemented by Sony in real camera/sensor.
Sony now has another solution to AF in liveview (including for video): A moveable pellicule mirror. Here is the patent.
http://www.freepatentsonline.com/y2010/0045853.html
The rumors are that two cameras with this design (A55, A33) will be released in September.
The “PD” at the left of the image could be “Phase Detectors”, instead of “photo diodes”
@Tony – Those descriptions are based on the information in the patent application, so “PD” actually does mean photodiode.
What exactly is/does Mirrorless mean?? I know I can understand a camera without a mirror but just how will it preform?? How will it be better?? And how much will it cost if and when if is marketed?? Just asking… thanx, Dabs.