Shooting Sports + Slow Motion (LX100 and GX7)

[sgreszcz]

Hi there,

I'm going to take some video of my brother when he races in the World Cup of Skeleton (where they throw themselves headfirst down an ice chute at up to 140 km/h).  I own a Panasonic LX100 and a newly-purchased GX7.  I'm planning on using the LX100 for the wider shots and when I want to rely on the detail that the 4k brings.  I plan on using the GX7 with my longer u4/3 lenses (like P35-100/2.8) and hope to be able to use the DTC functionality as well.

I have a few questions about techniques and settings needed to shoot fast moving sport, using 50fps (in the GX7), and potentially getting more slow-motion with something like Twixtor to interpolate frames.

Normally, I try to follow the 180 degree shutter rule for motion blur, and until now I've only had a camera that shoots 24/25/30 fps so I've kept the shutter speed fixed at 1/50 especially when indoors with 50Hz lighting.

I would like to try to record some of the bobsled and skeleton starts with the intent of slowing them down in post.  The GX7 has 50 fps.  If I record in 50 fps, should I be setting the shutter at 1/125 or should I be using something higher for sharper image capture, especially if I intend on using something like twixtor to make it look like even slower motion?

As far as shooting at 50 fps on the GX7 (28 Mbps), is there any loss in image quality compared to shooting at 25 fps (20 Mbps).  Is there any reason why I shouldn't always shoot at 50 fps just in case I want to slow anything down in the future?

Thank you for advise!

[fuzzynormal]

I own the GX7, North American specs.  If I shoot 60p with a 60fps shutter I do NOT get smooth slow-mo when conforming the footage.  I have to set the shutter to 125, then it's all good.  I found with slow mo you can push the shutter up a bit more if you like, but I keep it at 125 mostly.

With a PAL GX7, maybe a 100 shutter would work, not sure.  Give it a test and see.

Twixtor type plug ins are nice, but limited.  You can use it for very selective moments/images and it'll look quite decent, but don't expect to apply it to a long clip of various shapes passing through the frame and have it work well.  Edge warping can be an issue.  

[sgreszcz]

Thank you for the input.  Sorry for the basic questions, I've done some additional research (I was searching the archives for "sports" rather than the software tools "twixtor, or FCPx optical flow" so previously didn't get many results).

fuzzynormal, I think that I will just be using the software slowdown when I grab some footage of bobsled and skeleton starts (if I'm capable of getting any decent shots).

I've just started playing with the GX7.  I've previously used Olympus E-M5/E-P5/E-PM2 and ditched them due to the weak video codec, especially on wide/fast shots.  My first Panasonic (bought in November) was the LX100.  I like the GX7, but find it a bit "clunkier" to use than the LX100.  There are significant improvements in the LX100 like focusing speed (faster than any camera I've ever used), face/eye detection, iAuto-ISO.  I also love the manual LX100 controls, and not having/needing a mode dial.  I'm still trying to understand how the configuration settings on the mode dial work on the GX7 when there are already modes for P/S/A/M, Movie Mode.  I also like using monochrome in the EVF/LCD on the LX100 when using video with manual focus as the yellow focus peaking really jumps out.  I'm not sure if this is available on the GX7.

In summary, the suggestions I found for slow-motion camera settings are:

- Use the highest framerate you have,  ie 720p/60 is better than 1080p/30.  My (PAL) GX7 has 1080p/50 so I'll go with that.

- Use the highest shutter speed you have.  Less motion blur will help the software tools do the interpolation better, and motion blur can be added back in post.

- A simple background is best.  I'm not sure how I can best do this as the starts have the sledders oncoming and if I use a shallower depth of field to blur the background, there is less time that the althletes will be in the area of focus.  I'm going to try to experiment with this and cars or other quick moving objects.

- Another tip to get the right amount of motion blur is to calculate the 180 degree shutter speed based on the fps you are shooting at * the factor that you plan on slowing down the shot in post.  I guess this means that If I'm shooting 50 fps, and plan on slowing down by 50%, I should set the shutter to around 1/200.

I will play around with Twixtor (demo), FCPx Optical Flow, and the free GoPro Studio 2.5 with flux (which I've read is Twixtor under the hood).