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Lens resolution: your lenses are worse than 4k video
  • apefosapefos

    It seems that lens resolution will be an issue for the 8k video. In the lenstip website they do measurements about lens resolution in line pairs per milimeter (lp/mm) and also with resolution charts.

    The average resolution for a full frame lens is around 45-50lp/mm and a great m43 lens is around 77-82lp/mm. The resolution charts shows the lenses at around 2000 - 2600 lines resolution maximum in still photos. Using a full frame lens in m43 sensor is worse because the sensor magnify the center area so the lp/mm will be half compared to same lens in a FF camera, a focal reducer can help a lot.

    So the still lenses can work good up to 4k resolution, sometimes lower resolution than 4k video, and maybe for 8k video there will be the need of new special lenses, high price.

    Considering that the indie people can buy only low price lenses, so work with 8k video will not make sense. 4k video is the maximum resolution for our photo/still lenses, no matter they are m43, aps-c or ff lenses.

    Example: the 12-35 lens at f4 is around 77lp/mm in the image center, the GH4 sensor in 4k is 8.1mm height, doing the maths this lens will resolve around 1250 lines in GH4 4k video.

    The new full frame Sigma Art 20mm 1.4 can do around 47lp/mm, so it will resolve around 770 lines in GH4 4k video. With a focal reducer this can increase to around 1080 lines. Most good Full Frame lenses are around a 50lp/mm maximum, and this is stoped down to f5.6

    In a full frame camera, considering the sensor 36 x 20,25mm, this same sigma lens can resolve around 1900 lines.

    The RGB bayer pattern decreases the camera resolution a little bit, around 1,33x less than the pixel count, so a 2160p video will deliver a maximum 1620 lines. The GH2 is 1080p and is around 810 lines.

    Lens resolution is a good reason for Panasonic release new cameras with the multi aspect sensor, a bigger sensor can use more image area form the lens and record higher resolution, more lp/mm. The GH4 sensor is 8.1mm height, 1250 lines with the 12-35 lens. The multiaspect sensor with 3840x2160 pixels for video would be 10,09mm height, and could record 1560 lines from the same lens.

    All these maths shows that 4k video is the sweet spot resolution for a video camera and for the lenses we can buy, and all these maths are in image center, in corners the lenses resolution is worst.

  • 6 Replies sorted by
  • andyharrisandyharris

    I checked the lenstip reviews, they are measuring the lp/mm from raw images. I suspect the glass can deliver more.

    I believe that 8K will be better than 4K using the same lenses, in the same way that a GoPro 4K video is better than a GoPro HD video given almost the same lens tech and a small sensor. Or to put it another way, although you may end up with the same lp/mm between 8K and 4K, the lines on the 8K will look smoother.

  • VeskuVesku

    Some m4/3 lenses can give very sharp results with Olympus 50Mpixel.

  • DrDaveDrDave

    It remains to be seen what the effect will be of 8K, but right now we are kinda maxed out sharpness wise, but sharpness is just one part of the lens quality. I'm not totally convinced the lens focal reducer gives you that much boost in sharpness, but if it does, sounds good.

  • Vitaliy_KiselevVitaliy_Kiselev

    @apefos

    Do not worry so much. For now 4K is barely alive. And 8K require so large panels that it can be limited only to selected IMAX theaters.

  • apefosapefos

    Probably the focal reducer will not increase sharpness in the same reduction factor, because there are optics in the way. Maybe 770 lines will increase to around 1000 or 930 or less...

    770 x 1.42 = 1093, 770 x 1,31 = 1008, 770 x 1,21 = 931

  • B3GuyB3Guy

    Almost all things trickle down eventually. 8K will be around some day I'm sure. There's also the fact that acquisition resolution and final delivery don't have to be the same thing (in fact IMO it is better to overshoot). New technologies like shifting sensors and IMAX's new laser projection may some day open up the resolution floodgates. Is resolution THE single most important aspect of video capture ever? Nope. But going forward it will be one stylistic way to make footage unique, and having the right lenses will factor into that. Some of my best childhood memories were from going to the omnidome IMAX at the MN Science Museum and watching nature documentaries with swooping helicopter shots. Would those films be better in 8K 3D projected with laser? Heck yes. Would they need the right lenses/sensors/post-processing and everything? Yeah they would.

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