$ ffmpeg -framerate 1/5 -start_number 1880 -i zcsci_%02d.png -c:v libx264 -pix_fmt yuv420p out.mp4

ffmpeg version N-77432-gc0f67e1 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 5.2.0 (GCC)
  configuration: --enable-gpl --enable-version3 --disable-w32threads --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libdcadec --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-aacenc --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-decklink --enable-zlib
  libavutil      55. 11.100 / 55. 11.100
  libavcodec     57. 19.100 / 57. 19.100
  libavformat    57. 20.100 / 57. 20.100
  libavdevice    57.  0.100 / 57.  0.100
  libavfilter     6. 21.100 /  6. 21.100
  libswscale      4.  0.100 /  4.  0.100
  libswresample   2.  0.101 /  2.  0.101
  libpostproc    54.  0.100 / 54.  0.100
Input #0, image2, from 'zcsci_%02d.png':
  Duration: 00:00:10.00, start: 0.000000, bitrate: N/A
    Stream #0:0: Video: png, rgba(pc), 3840x2880 [SAR 12598:12598 DAR 4:3], 0.20 tbr, 0.20 tbn, 0.20 tbc
[libx264 @ 0000000000460720] using SAR=1/1
[libx264 @ 0000000000460720] frame MB size (240x180) > level limit (36864)
[libx264 @ 0000000000460720] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
[libx264 @ 0000000000460720] profile High, level 5.2
[libx264 @ 0000000000460720] 264 - core 148 r2638 7599210 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=1 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'out.mp4':
  Metadata:
    encoder         : Lavf57.20.100
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 3840x2880 [SAR 1:1 DAR 4:3], q=-1--1, 0.20 fps, 16384 tbn, 0.20 tbc
    Metadata:
      encoder         : Lavc57.19.100 libx264
    Side data:
      unknown side data type 10 (24 bytes)
Stream mapping:
  Stream #0:0 -> #0:0 (png (native) -> h264 (libx264))
Press [q] to stop, [?] for help
frame=    2 fps=0.0 q=-1.0 Lsize=     506kB time=00:00:10.00 bitrate= 414.9kbits/s speed=22.6x
video:506kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.160298%
[libx264 @ 0000000000460720] frame I:1     Avg QP: 6.42  size:382815
[libx264 @ 0000000000460720] frame P:1     Avg QP:19.58  size:134282
[libx264 @ 0000000000460720] mb I  I16..4: 69.0% 18.2% 12.7%
[libx264 @ 0000000000460720] mb P  I16..4:  0.4%  0.3%  0.1%  P16..4:  5.6%  3.3%  2.3%  0.0%  0.0%    skip:88.0%
[libx264 @ 0000000000460720] 8x8 transform intra:18.4% inter:8.0%
[libx264 @ 0000000000460720] coded y,uvDC,uvAC intra: 9.4% 10.9% 9.6% inter: 4.8% 3.9% 3.6%
[libx264 @ 0000000000460720] i16 v,h,dc,p: 96%  2%  1%  0%
[libx264 @ 0000000000460720] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 60%  4% 30%  1%  1%  1%  1%  1%  1%
[libx264 @ 0000000000460720] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 34% 22% 15%  5%  6%  5%  5%  4%  4%
[libx264 @ 0000000000460720] i8c dc,h,v,p: 90%  4%  4%  1%
[libx264 @ 0000000000460720] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0000000000460720] kb/s:413.68