Looks good, not that I understand it.
canon patent 02 11 09 - Canon Patents a New Live View Autofocus System

From Engadget via Photography Bay: http://www.photographybay.com/…..

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21 Comments

  1. This is how AF works at present: a partially reflecting main mirror reflects light to the viewfinder and any light passing through reflects off a sub-mirror to the AF sensor. The change just seems to be that the light that was going to the viewfinder now goes to the AF sensor and the light that was passing through and going to the AF sensor now goes to the main sensor for live view. If we assume that the light was split evenly before (and that is a big assumption, I’ll admit) then there should be no real difference in AF performance. If it the viewfinder got the majority of the light, then the AF performance will improve, but the live view image might have a bit more noise. The mirror can still swing up when you take the shot, so the noise will not be present in the final image.

    Of course, if you want to make videos in low light, then you can’t have the mirror clattering up and down and you’ll either want to use contrast detection AF or jack up your ISO and live with the noise.

  2. ISO sensitivity as measured by DXO has absolutely NO RELATION whatsoever to actual sensor sensitivity. DXO measures ISO by determining the point where highlights start to clip. The standard way is spot meter off an 18% gray area so that the image luminance level is set at 50% of the final image file. Andy Westlake has the explanation here:

    http://forums.dpreview.com/forums/read.asp?forum=1032&message=30685499

    In fact, DXO results have often been found to disagree with real world photos. For example, performance of Canon 5D2 vs 1Ds3 (latter in reality has better dynamic range) or performance of D90 vs D300 (noise level at high ISO). I won’t give a hoot about so-called scientific results if they have no bearing whatsoever on how real world photos turn out. Of course, you can always use your camera SOLELY to shoot brick walls, test charts, color charts etc etc. ;)

  3. Oh, thanks for the info, Gusto. Didn’t know those details about the DxO measurements. So what you say is, the D90 is actually not as much better than the D300 as the DxO ISO sensitivity suggests? If I remember correctly, the dynamic range is better as well though?!

  4. Photographer/Videographer on

    Despite of this (possible) new system, companies are working to improve contrast detection AF.

    So, hopefully we could get both systems, and if contrast detection AF is the only choice for a specific situation, it might be faster than the actual one.

  5. then live view mode, the coms will only get half of the light as well? new dslr’s iso performance will be damned

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