X8 SE preflight tips

by **Admin** 2021-05-05, 00:57

X8 2018
In my experience, the best looking video from the X8-2018 camera comes down to:

Low contrast scenery with good illumination is necessary because we don't have sufficient manual camera controls or firmware to handle difficult lighting
ISO 100 to maximize clarity by minimizing noise & the ill-effects of in-camera noise reduction
Proper exposure through manual Ev or spot-metering as appropriate (but no true exposure lock available)
Steady white balance per shot/clip (Sunny or Cloudy supposedly lock the WB)
F-Log to maximize dynamic range, details, and color correction flexibility
4K allows up to 2x reframing without losing resolution while publishing to 1080p
30 FPS avoid/reduce frame-rate induced choppiness with any significant movement (as is inherent to drone footage)
Motion rate thresholds are key to cinematic clips; keep movements smooth and slow
Antenna Boosters (Parabolic or Yagi-style) are often critical with the X8-2018 to maintain a steady FPV feed out to VLOS limits while maneuvering
Color correction with slight sharpening in post-production
Timeline awareness is necessary to ensure the timeline resolution and framerate in our NLE editor match our input clips, while at least matching or exceeding output resolution

We've already covered some best practices surrounding ISO 100 and exposure metering with the X8-2018 camera, but let us know if you have any further questions or experiences.

F-Log is only available in 4K video mode, so I want to reiterate that a proxy workflow can accommodate virtually any computer hardware for '4K editing' purposes since the original 4K files are only used in the final output-rendering step.

And when shooting in F-Log we should reduce the in-camera Style > Contrast/Saturation to somewhere below the default 64/64. I use between 50/50 and 60/60. The lower limit is driven by FPV feed 'washout' since there's no compensation feature. Otherwise, the lower limit could theoretically be zero, but some experimentation would be in order because low contrast could reveal more noise (I'm told). Speaking of color profiles, General/Vivid with Styles 64/64 selections produce an in-camera color-grade and exposure. That in-camera processing limits further corrections in post-production because these color profiles discard extraneous image information much like JPEG compression. So with General/Vivid the image could fall apart (solarize) while attempting additional corrections (color or exposure adjustments) in post.

Footage from the X8-2018 tends to look soft. That's not necessarily a bad thing because sharpening is an aesthetic preference that: (1) exceeds the native/natural sensor data, (2) is destructive when performed in-camera, and (3) can always be added in post-production.

I use the free DaVinci Resolve 16 largely for its powerful, node-based, color grading system. But that's serious overkill for this task because everything you're seeing in that vid is possible with layer-based, 8-bit, color-correction tools found in any advanced video editor today. So you will need something more capable than iMovie or Windows Movie Maker (Photos app video editor for Windows 10) because those don't have the necessary tools. But there's really no reason to use such light-weight editors today in light of Shotcut and other free or inexpensive options. I can post some Shotcut, VSDC and DaVinci Resolve (all free editors) color correction tips with screen shots as necessary.

Basic color correction tools include:

3D LUT support (look-up tables; color space mapping or to create preset looks; free LUTs download)
exposure (gamma or exposure curve)
dynamic range (set white & black points/levels or exposure curve with offset)
saturation (re-saturate F-Log while adjusting LUT intensity)
sharpening (a little goes a long way)
brightness (not always necessary with 'gamma' control or exposure curve)
contrast (not always necessary with white/black 'level' control or exposure curve)
white balance (color temperature; can create a 'look' if we're not interested in preserving skin tones)
scene matching (copy-&-paste color correction layers/nodes/filters to related clips)

Other desirable tools include:

masking by keyframe (such as to enhance the sky separately from the ground for an HDR look)
noise reduction (HQDN3D; for high ISO footage)
color grading wheels (separate shadows, midtones, highlights; best when creating a 'look' while isolating skin tones in advanced NLEs)
rotate and scale by keyframe (for horizon-tilt correction if necessary)

Some non-linear video editors (NLE's) with all these features include:

Shotcut (free; cross-platform)
VSDC Free Video Editor (free; Windows only)
LumaFusion ($30; iOS only)
Filmora ($100; Windows and MacOS)...and other prosumer NLE's
DaVinci Resolve (free; cross-platform)...and other professional NLE's

x8 2020

GENERAL ADVICE:
- Download the correct '2020' version of the app; spend ample time familiarizing yourself with the user's manual and particularly the app layout
- Top off your batteries: (1) drone, (2) controller and (3) phone
- Don't update the firmware right away; update only when deemed safe to do so by users in this thread; restart the drone after any such update or calibration.
- Wait until you're in the field to perform a compass calibration; and away from all metal including sidewalks (rebar), watches, etc. This can be a onetime procedure, although expect the Navi app to suggest a compass cal when changing flying regions or when encountering strong magnetic fields. Sometimes simply moving the drone a few meters will satisfy the app, thereby avoiding unnecessary compass calibrations.
- Consider a gimbal calibration to include 'advanced' manual tweaks on a perfectly level surface (bubble level & Lazy Susan), performed at least twice on two axis 90 degrees apart. This calibration should follow any compass calibration (per JNoake's findings below).
- Use a U3 V30 microSD in the drone, and reformat in the drone (FAT32 format; found deep in the camera settings)
- Calibrate the controller (sticks) and adjust Yaw settings according to simplemind's experience:
  - Yaw distance: 10%
  - Expo on Yaw: 90%
  - Yaw sensitivity: 100%
  - The X8 2020 comes to a lazy stop when yawing. To stop the yaw immediately do a quick/sharp input in the opposite yaw direction.
BEFORE EACH FLIGHT:
- Always remove the gimbal protector BEFORE powering the drone; consider it a deliberate 5th step in unfolding the drone; and get a proper gimbal protector
- Set the drone on a relatively flat surface while observing the gimbal's ground-clearance as necessary for the camera startup sequence (preferably using a relatively stiff landing pad)
- Check prop security by holding each motor in sequence while twisting its prop lightly to observe prop interlocks; leaving the props unfolded for takeoff
- Recheck gimbal cover removal, and do a final squeeze on the battery without engaging the unlock tabs to ensure it's secure
- Start both drone and controller (any order AFAIK), but then wait for the orange flashing connection light to turn white on the controller before entering the Navi app.
- In the meantime, start a screen recorder on your phone and perform a multi-app preflight as follows:
  - Check 'UAV Forecast' app (or equivalent) for wind speeds and satellite KP value.
  - Check an airspace app for any flight restrictions in your immediate area
  - Check the Fimi Navi app for FPV video feed, and then proceed to explore all functions of the D-Pad on the controller such as:
  - Dobber left on the D-Pad to check all your settings (or three dots in the upper corner of the app)
  - Pay particular attention to the RTH altitude and ensure Failsafe is set to RTH as well
  - Dobber right on D-Pad to check the overall Drone Status where you should observe all 'Normal' with 'Weak' interference
- Perform a FULL CAMERA SETUP; for the best results select the following:
  - Normal video mode
  - 4K@30
  - Average metering (or Spot metering if you're familiar with the pro's and con's)
  - Auto EV (exposure value) vs. Manual ISO 100
    - To ensure the best possible results in good lighting select ISO 100 manually. This is the least sensitive sensor setting, which hides noise while maximizing image detail, as it avoids softening through in-camera noise-reduction.
    - Bright sand or snow may require an ND filter (neutral density filter) in addition to Manual ISO 100 to avoid over-exposure as the maximum shutter speeds are reached.
    - Auto EV may be used in all lighting conditions on the assumption that ISO 100 is selected automatically in sufficient lighting. In reduced lighting, Auto EV preserves shutter speed (to avoid blurring) through increased ISO as appropriate. Metering becomes more critical with Auto EV, but the right scroll-wheel on the controller can be used to bias/adjust the EV on-the-fly.
  - General color or perhaps Vivid color, unless you plan to perform FLog color-correction in post production; recommend the Shotcut video editor as a minimum to edit 4K footage due to its auto-generated, edit-friendly, proxy file support.
  - H.265
  - High bitrate Video Quality as the LAST step in your camera setup due to Medium quality override with some camera settings. Note that 'High' provides up to ~60Mbit/s bitrate at 4K@30 (despite Fimi's 100Mbit/s claim), which combined with the H.265 codec is equivalent to 90Mbit/s H.264 in video 'quality'
  - Flip to Photo mode and repeat as required
- Remove any Bluetooth wearables and turn off Bluetooth and WiFi on your phone while retaining 4G data for the maps (so not simply Airplane mode)
- Check the controller's orange button position (not in RTH 'home' position)
- Generally stand behind the drone for all takeoffs and landings to maintain easy orientation in close proximity
- Ensure 'GPS Ready to Fly' is displayed
- Start recording on the camera
AFTER TAKEOFF:
- Ensure video is recording by observing the cumulative counter (the start/stop button alone can be confusing)
- Monitor any messages about the compass or other hardware components (land immediately and restart)
- Always face the drone with the controller at any significant range
- Use a spotter to keep the drone in sight
- Fly upwind at longer distances; build a habit of descending in strong headwinds, consistent with obstacle clearance.
AFTER LANDING:
- Stop your screen recorder (Fimi drones stop recording automatically upon landing)
POST PRODUCTION:
- You may find the following free 3D LUTs useful.
  - LUTs are supported by all serious video editing software including Shotcut (free), DaVinci Resolve (free), etc. They're used to apply 1-step color-space conversions, color-corrections and/or color grades to include specific 'looks' (such as retro film, vignette, orange-teal, etc). After applying a LUT, simply adjust Saturation and perhaps Contrast to taste.
- You may find the following HandBrake presets useful to convert 'variable' frame rates to 'constant' frame rates.
  - The two, Fimi-specific, HandBrake presets (included in the download above) are intended to convert Fimi's dubious variable framerate into edit-friendly constant framerate video files. Note that you can optionally select a different constant-framerate on the 'Video' tab in Handbrake after applying one of the Fimi presets. The resulting files can be used in lieu of the originals. That's because the preset RF:17 (on the Video tab in HandBrake) is considered 'visually lossless' so these files become apt replacements for your originals for editing purposes. Unfortunately, these replacement files are 5x larger than the originals. Likewise, RF:10 is considered 'placebo' (overkill) and results in 6x larger files but notably requiring 4x longer to create. RF:0 is 'lossless' (serious overkill for our purposes) with a corresponding increase in file-size and perhaps a full day to create from a 25 minute drone flight recorded at 4K@30, High, H.265. So RF:17 is preset and recommended when replacing originals to achieve a constant framerate for editing. For the techie-types among us, reference the .json preset files to reveal the specific 'x264' (open source software encoder) parameters used by the Fimi-specific presets to generate constant bitrate files without frame drops or skipping (specifically the 'dct_decimate=1' parameter).
  - You can skip the clunky HandBrake workaround if you're a Shotcut video editor user. We often recommend this relatively easy-to-learn and use editor for hobbyists since it has all the essential features necessary to process 8-bit drone video. Simply select a clip in Shotcut and select Properties > Advanced > Override frame rate > Frames/sec: 29.97 > Frame rate conversion: Blend.