For 4k, your lens needs to optically resolve at least 12 MP (4000*3000 pixels) photo resolution. I'd suggest checking DxO Mark lens test results for suitable models: http://www.dxomark.com/Lenses (and check the button "Micro 4/3" on the right).
It turns out that none of the tested MFT lenses actually resolves 12 MP. Only a few primes (such as Panasonic's Leica-branded primes) reach more than 10 MP. If you want real 4K resolution, you'll probably need professional cinema lenses like the Schneider Xenon/Super Angulon: http://www.ephotozine.com/article/schneider-kreuznach-14mm-30mm-m43-lens-hands-on-26227
Best idea to move away from "4K lenses" and "optically resolve at least xxMP". And no, do don't need " professional cinema lenses like ... ".
You can find samples / MTF charts, etc at any review site or here in any lens topic on PV.
Lenses don't "resolve megapixels." They resolve line pairs per millimeter (lp/mm) and here's a good article about how that relates to what your camera can resolve:
Taking a conservative resolution reduction of 24% for all the filtration, the best a 4k high resolution camera would be capable of seeing are nearly 35 line pairs per millimeters before electronic processing. This limit is determined solely by the video camera at the sensor level as it generates a RAW signal. As stated above, motion picture lenses easily exceed theses values by a good margin and modern lenses have the capacity to resolve more than 5 times this requirement.
If you think your 4k video images do not look as good as they should, by all means have your lens checked but realize the camera is still by far the primary limitation for maximum resolution.
Even if it mattered, where is this 12 megapixel number you are quoting come from? The GH4 records, at most, 8.8 megapixels in video mode.
Thank you for your reply. Good article to read.
Right now I am shooting on the Leica 42.5 1.2 a very sharp lense. So do I always achieve best quality when shooting in MOV, 4K-mode with 100mbits? How good would be the FullHD 200mbits mode be as it can capture higher mbit-rates?
I am also looking for a very sharp and fast wide angle lense to shoot in 4K/FHD on the DJI Ronin-m. Unfortunately, rolling shutter in 4k mode on the GH4 ist quite strong. But do you have any recommendations? I though about the Panasonic Leica DG Summilux 15mm F1.7!?
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