Wednesday, May 22, 2013

HDR Time-lapse Workflow for Nikon D80

Making an HDR (High Dynamic Range) time-lapse movie involves a series of procedures that require planning, a little math, camera settings and post processing. In some shooting situations, you could be in rush and might forget one or two key steps that end up realizing a less ideal production after the session. During the workflow, especially in the shooting sesison, I would always go through my checklist if possible to make sure those key steps are followed and properly setup. I would like to share with you such a checklist I have developed for my camera Nikon D80. This workflow should be applicable to most Nikon DSLR models.
The workflow: Planning → Camera settings → Intervalometer settings → Shooting session → HDR tome mapping → Time-lapse movie making.

Planning

Depending on different scenes, the properly selected interval between each shot determines how the frames will flow in your final movie. Here is a table of typical intervals for popular time-lapse scenes.
Typical ScenesRecommended Interval
Fast moving clouds
Moving traffic
Drivelapse (shooting while driving)
1 second
Sunset / Sunrise
Moon near horizon
Slow moving clouds
Crowds
1-3 seconds
Moving shadows
Sun or moon acrossing the sky (wide angel without clouds)  
15-30 seconds
Stars or star traces15-60 seconds or more
Fast blossom flwoers
Fast growing plants
90-120 seconds
Construction site5-15 minutes

Camera (Nikon D80)

  1. set the camera on a solid tripod
  2. turn VR off
  3. connect a intervalometer to the camera
  4. focus on your subject with AF, then turn AF off; or just use manual focus
  5. set to manual (M) mode
  6. set shooting mode to Continuous (multiple shots)
  7. set image quality to Fine (jpeg only, no RAW if you experience slow buffering )
  8. set WB to a manual mode according to the shooting condition (Daylight, Shade, etc.)
  9. set Multiple exposure to ON
  10. set ISO based on lighting and noice tolerance
  11. set aperture based on the required DOF (see note below for avoiding flickering)
  12. set shutter speed based on the required proper exposure
  13. take a test shot, and check the exposure histogram and depth of field
  14. if for HDR, set bracket by pushing BKT button while thumb dialing to turn ON ABE bracket to 3F
  15. keep pushing BKT while index finder dialing to adjust the stops (0.3 weakest to 2.0 strongest)
  16. take another test HDR shot  (see Intervalometer settings), and check the histograms of the 3 shots
  17. create a new folder for this time-lapse session
  18. Other optional settings
    • turn Beep off
    • turn Image Review off.
    • turn Exposure Compensation to OFF

Note: Tips to avoiding flickering
  • keep the same exposure for each shot, 
  • shorten interval between shots whenever possible,
  • keep f/8 or wider when possible. Smaller aperture (< f/8 or further) may cause shutter not going back to the exactly same position for each next shot, thus causing artificial flickering.

Intervalometer


  1. Delay (in seconds): A delay to release shutter of the first shot. Normally set to 0.
  2. Long (in seconds): 
    • in regular mode (M), it is the time enough to cover 1 shot. Set it to equal to or a liitle longer than the shutter exposures time;
    • in HDR mode (M), it is the time enough to fire all 3 shots. Set it to equal to or a little longer than the sum of shutter exposures of the 3 shots;
    • in Bulb mode (B), it is the time to hold the shutter open. 
  3. Interval (in seconds): it is the time between two shutter releases. (Note, for HDR, one release has 3 shots)
  4. N: the number of shutter releases. Considering each will consume at lease (Long + Interval) seconds when you calculate the total time for completing the shooting session.

Shooting Session

Now, you are ready to fire the shooting session. During the session, when in a windy day, try to hang more weight to the tripod for stability.

HDR Tone Mapping

There are certain HDR software for tone mapping the bracketing shots (one normal exposed, one under exposed and one over exposed with +/-xEV). I recommend HDRSoft's Photomatix Pro.
For example, if you have 3000 HDR shots in your session, use the middle set of 3 as the benchmark to develop the tone mapping first with Photomatic Pro. With fine tuning and adjustment, you save this as the template for all your 300 shots in a batch processing in Photomatix Pro, this will take quite a long time. I typically run it overnight with my iMac. Name a specific directory for your tone mapping output. After the process finishes, you will have 1000 tone-mapped images in sequence and ready for your time-lapse movie.

Time-Lapse Movie Making

As a Mac fan, I always use Quicktime Pro to make the time-lapse movie. After invoking the Quicktime Pro 7, go to File | Open Image Sequence..., in the Open window, browse to your tone-mapped image directory and just select the first image of the sequence. Quicktime Pro 7 will ask you to specify frame rate (I typically choose 24 fps). Then all images in the sequence are loaded. With resizing for the movie (1920x1080, or the size for your targetted playback device), you then save the movie by selecting File | Export..., with video quality settings at your choice, then save to a movie in your chosen format (Quicktime .MOV, H264 .mp4, or others encoders). 

With more practice, I hope you will have developed a better workflow for your specific needs. If you like to see some HDR time-lapse movies I have made, see them in my gallery.

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