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video capability and what to look for in a digital camera

dSLR vs mirrorless cameras

  • video is one area where mirrorless cameras are FAR better than dSLRs
  • this is because one cannot use the viewfinder in video mode on a dSLR as the mirror is up and blocking the viewfinder during video, so you MUST resort to other means such as “Live View mode” on the rear LCD or an external monitor.

camera features and impact on video quality

image stabilisation

  • camera shake is perhaps the Number ONE problem that detracts from video viewing
  • professionals have historically got around this by either:
    • mounting camera on a video tripod which allows fluid panning, or,
    • run and gun (walk with the camera) mounted to a big, heavy, expensive and difficult to use gimbal stabiliser system
  • BUT times have changed and we now have extremely good in-camera image stabilisation in many cameras
    • the leader in this movement was Olympus with their superb 5 axis sensor based “IBIS” in-body image stabilisation which for the 1st time gave us very well controlled camera shake in video mode
    • most of the other camera manufacturers have been slow to take this on, but now we have excellent systems from:
    • Canon are yet to release a full frame mirrorless camera with IBIS so you are stuck with a much less effective optical IS on some of their lenses

focus capabilities

sensor and camera processing image quality

  • there are MANY factors which contribute to video quality that are determined by the camera's design and processing functionality
  • most modern sensors have a resolution that is greater than the desired video resolution, and most have a different aspect ratio, and this means that techniques must be employed to address these differences and the options here include (from best to worst):
    • “oversampling”
      • this uses all the sensor's pixels in a complex algorithm to generate a lower resolution video output thereby hopefully being able to create less image noise, less aliasing artefacts and high image detail, but this does come at a cost of higher power consumption and heating and less battery life
      • this is why the Sony a7 III full frame mirrorless camera and Nikon Z6 have much better video quality than their more expensive higher resolution models, the Sony a7R III full frame mirrorless camera and Nikon Z7 which use line skipping
    • pixel binning
      • this combines data in adjacent pixels to create a lesser number of pixels but with hopefully better signal to noise ratios giving lower image noise
    • line skipping
      • this just throws away pixels to reduce the resolution but does not have the image improvement benefits of the above two techniques
    • cropping
      • this is worse than line skipping because it forces one to use a cropped mode which not only changes perspective for a given lens but you do not gain any improvements in image quality however it is the least processor intense method and thus uses less battery and generates the least heat
      • examples of this are the new Canon EOS R camera
  • presence of a optical low pass or anti-aliasing filter on the sensor
    • this reduces moire artefacts but also makes the image potentially softer by adding in some blur
  • degree of rolling shutter
    • this mainly effects panning or moving subjects causing a sloping subject
    • this has been improving with sensor technology and hopefully soon sensors with global electronic shutters will eradicate this
  • image processing algorithms and modality
    • color space aspects 8 bit vs 10 bit vs 12 bit; 4:2:2; etc
    • image contrast issues - how well it copes with post-processing grading
    • RAW output and compression issues
    • video resolution (1080 vs 4K vs 8K)
      • Cinema 4K: 4096×2160 1.85:1
      • QFHD 4K: 3840×2160 16:9
    • video capture rates
      • the standard film look is 24p, many prefer 30p
      • those wanting to do slo-mo will want 60p/120p or even faster rates such as 180p or 240p
    • video output formats
      • MOV, MP4, AVCHD Progressive and AVCHD formats
      • professional 400Mbit ALL-I intraframe codec for 10bit 4K 4:2:2
        • but these do give file sizes 3x the size of 150Mbit interframe codecs and requires 300MB/s UHS-II cards
      • ‘Cinelike D’ and ‘Cinelike V’ as well as ‘Like 709’ for compatibility with HDTV
      • advanced V-Log L video mode and VLogL View Assist Function
      • Hybrid Log Gamma with view assist feature for HDR shooting
      • 5K 10bit “Open Gate” High Resolution Anamorphic Mode

camera functionality to assist video use

  • mic in port
  • headphone port
  • audio controls
  • Zebra pattern - to watch white wash-out
  • hotshoe adapter powered through the hotshoe to give Phantom power to external mics
  • embedded SMPTE-compliant Time Code
  • Gain and Shutter Angles
  • waveform or vectorscope monitor display
  • luminance level settings
  • control over the highlight response rolloff (Knee point and Knee Slope)
  • clean RAW video out via HDMI
  • speed and capacity of memory cards
  • battery holder grip to provide additional battery life
  • maximum duration of video (many are limited to under 30 minutes to avoid regional tax laws which place higher taxes on “video cameras”)
  • fully articulating LCD screen for selfie vlogging
  • choose which broadcast safe RGB luma range to use (0-255, 16-235 for the safe range, or 16-255)
photo/video.txt · Last modified: 2019/02/18 11:07 by gary1

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