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Thread: Live View Implementation

  1. #1
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    Default Live View Implementation

    Live-Preview feature has been a great advantage over DSLR for years, until Olympus introduced very 1st DSLR live-view on Jan 2006. Subsequently almost all major manufacturer have to join in this feature war and live-view has become one of the big consideration feature for consumer, like image stabilization, dust removal etc.

    However we can see 2 tracks of implementation of live-view now.
    1. Having additional live-view sensor,
    2. Using main image sensor for live-view.

    Olympus started with 1st choice, Panasonic join in later. This year Sony model is using similar concept.
    However the 2 big giant choose 2nd way.
    There are pro and cons of course. Mainly 1st way allow continuous focusing, so good for motion, 2nd allow more realistic result view, so good for studio.

    Which kind of implementation do you think is more "correct" for DSLR live-view?
    What other issues do you foresee that will kill the live-view implementation?
    Sony Alpha

  2. #2
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    Default Re: Live View Implementation

    Alright. What about are you happy with your current live view system? Any wish list for the future live view development?
    Sony Alpha

  3. #3

    Default Re: Live View Implementation

    Quote Originally Posted by yannh View Post
    Live-Preview feature has been a great advantage over DSLR for years, until Olympus introduced very 1st DSLR live-view on Jan 2006. Subsequently almost all major manufacturer have to join in this feature war and live-view has become one of the big consideration feature for consumer, like image stabilization, dust removal etc.

    However we can see 2 tracks of implementation of live-view now.
    1. Having additional live-view sensor,
    2. Using main image sensor for live-view.

    Olympus started with 1st choice, Panasonic join in later. This year Sony model is using similar concept.
    However the 2 big giant choose 2nd way.
    There are pro and cons of course. Mainly 1st way allow continuous focusing, so good for motion, 2nd allow more realistic result view, so good for studio.

    Which kind of implementation do you think is more "correct" for DSLR live-view?
    What other issues do you foresee that will kill the live-view implementation?
    There is no right or wrong. Just which one you prefer.

  4. #4
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    Default Re: Live View Implementation

    Quote Originally Posted by yannh View Post
    However we can see 2 tracks of implementation of live-view now.
    1. Having additional live-view sensor,
    2. Using main image sensor for live-view.

    ...
    Which kind of implementation do you think is more "correct" for DSLR live-view?
    What other issues do you foresee that will kill the live-view implementation?
    From a technical point of view, 1) is a convenience feature, similar to an angle viewfinder or a clip-on video camera for the optical viewfinder, whereas 2) results in a more accurate electronic viewfinder.

    With the common autofocus SLRs, there are three planes of focus - the sensor, the focusing screen, and the AF sensor. It requires quite a bit of precision to match them all, and especially to keep it all in sync if the camera gets bumped around, or the focusing screen gets swapped, etc. This is presumably where the entire front-/backfocusing and lens alignment issue comes from. Depending on how an additional live view sensor would be used, this could introduce yet another focus plane that may be out of alignment. Similar things go for accurate framing.

    The beauty of using the same sensor to implement an electronic viewfinder and to take the photo is that there is inherently no adjustment/calibration problem. It's basically a self-correcting system.

  5. #5

    Default Re: Live View Implementation

    the problem with using the main sensor of course is that the main autofocus system is bypassed and to have autofocus, the camera would either have to lower the mirror or use contrast detect from the main sensor which with current technology is slower and less versatile than the main AF system...

  6. #6

    Default Re: Live View Implementation

    Wonders that for the first choice with a separate sensor, is the sensor drawing image info from the viewfinder part? If so, the autofocusing function will not be interupt, just that making ur eyes seeing the viewfinder info without putting eyes close to the window, but looking at the LCD. If that's the case, we still got the WYSIWYG effect, will be more prefer this way.

    No point using the main sensor actually since all the calibration and alignment things are done, just get info after the system can already.

    Correct me if wrong...

  7. #7

    Default Re: Live View Implementation

    Quote Originally Posted by emerald View Post
    Wonders that for the first choice with a separate sensor, is the sensor drawing image info from the viewfinder part? If so, the autofocusing function will not be interupt, just that making ur eyes seeing the viewfinder info without putting eyes close to the window, but looking at the LCD. If that's the case, we still got the WYSIWYG effect, will be more prefer this way.

    No point using the main sensor actually since all the calibration and alignment things are done, just get info after the system can already.

    Correct me if wrong...
    Check the A350 LV implementation... Basically the AF and metering paths are not interrupted. The only thing that happens is that within the viewfinder prism, the light is redirected to a small sensor instead of out the viewfinder. So it's a good WYSIWYG effect with no need to drop the mirror down before shooting.
    Alpha

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    Default Re: Live View Implementation

    Quote Originally Posted by theRBK View Post
    ... or use contrast detect from the main sensor which with current technology is slower and less versatile than the main AF system...
    ... but also the most accurate. At least, it gives you a choice. E.g, I wouldn't want to use the present generation of contrast based autofocus for action sports, but it should work extremely well for still lives. It's a tradeoff - fast and complicated and potentially out of adjustment vs. slow, simple, and inherently accurate.

    "Live" sensors that take the image of the focusing screen are modern versions of angle viewfinders - sometimes very convenient, but they don't gain any technical advantage.

  9. #9
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    Default Re: Live View Implementation

    Quote Originally Posted by theRBK View Post
    the problem with using the main sensor of course is that the main autofocus system is bypassed and to have autofocus, the camera would either have to lower the mirror or use contrast detect from the main sensor which with current technology is slower and less versatile than the main AF system...
    I'm a little confuse here. Isn't all the current AF system using contrast detection? Beside using the focusing sensor, how to perform focusing on main image sensor?

    Quote Originally Posted by LittleWolf View Post
    ... but also the most accurate. At least, it gives you a choice. E.g, I wouldn't want to use the present generation of contrast based autofocus for action sports, but it should work extremely well for still lives. It's a tradeoff - fast and complicated and potentially out of adjustment vs. slow, simple, and inherently accurate.

    "Live" sensors that take the image of the focusing screen are modern versions of angle viewfinders - sometimes very convenient, but they don't gain any technical advantage.
    Most accurate is what sense? maybe DOF, what else? What other method of AF we have beside contrast base? And what technical advantage you're talking about?
    Sony Alpha

  10. #10

    Default Re: Live View Implementation

    Quote Originally Posted by LittleWolf View Post
    ... but also the most accurate. At least, it gives you a choice. E.g, I wouldn't want to use the present generation of contrast based autofocus for action sports, but it should work extremely well for still lives. It's a tradeoff - fast and complicated and potentially out of adjustment vs. slow, simple, and inherently accurate.
    agreed... though with the advance of technology, contrast detection could possibly catch up with the speed of phase detection autofocus (conventional DSLR autofocus)...

    Quote Originally Posted by yannh View Post
    I'm a little confuse here. Isn't all the current AF system using contrast detection? Beside using the focusing sensor, how to perform focusing on main image sensor?

    Most accurate is what sense? maybe DOF, what else? What other method of AF we have beside contrast base? And what technical advantage you're talking about?
    most if not all SLR autofocus cameras, film and digital, use an autofocusing system called phase detection autofocus, which requires a complex autofocusing system... whereas most point-and-shoot cameras use contrast detection autofocus which utilize the main imaging sensor... in the case of some of the DSLRs which utilize the main sensor for autofocus in liveview mode (some use main sensor for liveview but flips the mirror down to activate the main phase detection autofocus system), contrast detection autofocus is used... its just that at the current state of technology, contrast detection autofocus is not as fast as phase detection autofocus... contrast detection could be more accurate in that the detection system is measuring the sharp contrast that comes with an image in focus on the main sensor, whereas for phase detection the system is measuring distance to the subject, which then needs to be translated into how much the lens needs to be adjusted so that the image of the subject can achieve focus onto a third party, the main sensor, and this might introduce the possibility for slight errors...

  11. #11
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    Default Re: Live View Implementation

    Quote Originally Posted by theRBK View Post
    agreed... though with the advance of technology, contrast detection could possibly catch up with the speed of phase detection autofocus (conventional DSLR autofocus)...

    most if not all SLR autofocus cameras, film and digital, use an autofocusing system called phase detection autofocus, which requires a complex autofocusing system... whereas most point-and-shoot cameras use contrast detection autofocus which utilize the main imaging sensor... in the case of some of the DSLRs which utilize the main sensor for autofocus in liveview mode (some use main sensor for liveview but flips the mirror down to activate the main phase detection autofocus system), contrast detection autofocus is used... its just that at the current state of technology, contrast detection autofocus is not as fast as phase detection autofocus... contrast detection could be more accurate in that the detection system is measuring the sharp contrast that comes with an image in focus on the main sensor, whereas for phase detection the system is measuring distance to the subject, which then needs to be translated into how much the lens needs to be adjusted so that the image of the subject can achieve focus onto a third party, the main sensor, and this might introduce the possibility for slight errors...
    Thanks for he explanation. I have better understanding now.
    Sony Alpha

  12. #12

    Default Re: Live View Implementation

    no prob

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