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  • Guspaz - Tuesday, May 27, 2014 - link

    Wait, so the laser rangefinder only works on distances less than two feet? Doesn't that render it rather useless for anything but macro shots? Reply
  • coburn_c - Tuesday, May 27, 2014 - link

    I believe he said instant detection of the first two feet. So the camera knows whether it can skip the macro range before it even begins to find focus. Reply
  • coburn_c - Tuesday, May 27, 2014 - link

    **Actually it says that exactly, read the article. I don't think it even works in the macro range, it just tells it whether to turn on macro focus or not. I imagine it only work in indoor scenarios, where there isn't enough contrast to do a quick focus and not too much background IR to obscure the beam before it bounces back. Reply
  • Guspaz - Tuesday, May 27, 2014 - link

    Except, contrast-based autofocus should be able to tell if the current focus setting is in focus instantly, and chances are that whatever you're taking a photo of is pretty close to the previous thing you took a photo of anyhow. Unless I'm taking macro shots, the camera will never check the macro range in the first place, and even if I am taking macro shots, instantly measuring the focal distance with a laser doesn't obviate the need to physically move the lens. Reply
  • coburn_c - Tuesday, May 27, 2014 - link

    Actually it doesn't 'tell instantly'. It moves through the focal range until it finds a best case. The 2ft instant range finding eliminates part of the range it moves through. Again, in plain english in the article and painfully obvious if you've ever watched a macro lens focus. Reply
  • Impulses - Tuesday, May 27, 2014 - link

    Plus CDAF never knows which way it needs to move first, which is something this might help with. Reply
  • patrickjchase - Wednesday, May 28, 2014 - link

    Contrast-based autofocus can *never* tell if it's in focus instantly, because it can't distinguish:

    1. A low-contrast scene that is in focus
    2. A higher-contrast one that is out of focus

    The only way a contrast-based system can distinguish those 2 cases is by "hunting" and taking multiple measurements until it finds a setting that yields maximum contrast.

    That's the *entire* reason why phase-based systems are strongly preferred for any application that requires low shutter lag. Phase-based systems can tell how far out of focus they are and in which direction with a single measurement.
  • patrickjchase - Wednesday, May 28, 2014 - link

    I probably should acknowledge that phase-based systems do have pathological cases where what I said isn't true. For a good time, try setting your phase-based SLR to use a single AF sensor, and then aim it such that that sensor is orthogonal to a pattern of regular lines. Doing so causes phase ambiguity (i.e. the camera can't tell 90 from 540 from 810 degrees) and often results in endless hunting. Reply
  • usama_ah - Tuesday, May 27, 2014 - link

    Seems that it doesn't "only work" in ranges < 2 ft, but that the biggest advantage ("greatest benefit") is seen in detection of distances within the first two feet. An advantage implies a comparison to another system, in this case the contrast-based AF system. The laser works beyond 2 feet too but it seems success is less likely due to signal-to-noise issues (worse when outdoors? since greatest benefit of laser system is seen indoors). If there is not enough signal (transparent object, too bright to see the signal) or too much signal (due to multiple returns , reflections) then the system can drop to the contrast-AF for focusing, which will assume at first that the object is >2 ft away since usually this laser system can nail the first 2 feet. (but if needed the contrast-AF system can still focus for objects <2ft if for some reason the laser failed there). That was what I got from reading the article. Reply
  • krazyfrog - Wednesday, May 28, 2014 - link

    The short distances are where it is needed most. Cameras struggle with focusing on objects that are too close to the lens and often take the longest to focus on closer objects whereas focusing on far away objects is near instantaneous on most cameras. The laser system should help make it faster to focus on closer objects than traditional contrast-based methods. Reply
  • Impulses - Tuesday, May 27, 2014 - link

    And selfies perhaps? They also state it allows CDAF to skip the 2ft range tho, which might prove useful for other types of shots... If the laser detects all subjects are beyond 2ft then CDAF can skip right over that range, CDAF works by comparing contrast back and forth as it moves the AF point so shaving off a range from the comparison could speed it up under certain situations.

    What's the reason that CDAF for phones lags so far behind high end CDAF on mirrorless cameras anyway? I can understand point and shoots just don't have the processing power, but you'd think phones have way more processing than even high end M4/3 & NEX cameras... Or is it a function of sensor size that somehow allows for better CDAF?

    The only thing PDAF (as used on DSLR) still does better is tracking, which is why Sony/Fuji/Olympus have gone with a hybrid approach that dedicates certain pixels to PDAF (but you can't have to many or the image suffers). Canon's gone with their new DualPixel tech on the 70D it seems, and Panasonic's developing a system that compares out of focus areas (GH4) using purely CDAF.
  • coburn_c - Tuesday, May 27, 2014 - link


    I imagine the bigger sensors in a proper DSLR let in more light and can therefore do finer contrast differentiation.
  • Impulses - Tuesday, May 27, 2014 - link

    DSLR don't use CDAF tho, 'least not under most circumstances... But yeah, the sensor size of mirrorless APS-C & M4/3 cameras might be the reason CDAF is so fast there, although they used to be as slow as any P&S that also uses CDAF, they just refined it over time... So I'm not sure it's an inherent sensor size advantage.

    Wouldn't a larger sensor actually create less contrast in many situations tho? (specially when you open the lens up and have less depth of field) DSLR use CDAF with live view I think but they use a completely separate PDAF sensor that's nowhere near the image sensor (that's where part of the light reflected by the mirror goes).

    PDAF has been refined for even longer since it goes back to SLR days... (pre-digital photography)
  • Impulses - Tuesday, May 27, 2014 - link

    P.S. Where's Brian when you need him, he'd school us... :p In all seriousness, I'm sure he'd have some interesting commentary on this tho. Reply
  • hrrmph - Tuesday, May 27, 2014 - link

    Early reports at PCMag are that it doesn't feel fast at all. Reply
  • melgross - Wednesday, May 28, 2014 - link

    The biggest deal here is that this will assist indoors, where the light level is low. That's always the most difficult time a camera has. Outdoors, almost any focussing scheme will be fine, as long as the manufacturer does a proper job with it. Reply

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