As you scroll through the thousands of GoPro action videos on YouTube, you will find that the very best use Slow Motion at some point during the video.
There can be a lot of confusion for new users on how Slow Motion can be used, terms such as frames per second and flux can intimidate people who have never used this feature.
If you are wanting to venture into the world of Slow Motion, the GoPro offers you a number of different options. When considering which method to use, you need to assess both the conditions you are filming in, as well as how you are planning to edit the footage to ensure you get the best outcome.
High Frame Rate
One of the most effective ways to film in Slow Motion on the GoPro is by increasing the Frame Rate. The Frame Rate is the number of images that the camera captures in a second. Typically a video is recorded and played back at approximately 30 frames per second (FPS), however the GoPro gives you the option to film anywhere between 15 and 240 frames per second.
By increasing the frame rate when filming, and then playing the footage back at a slower frame rate, you can create a slow motion effect with very little editing. For example if you shot a sequence in 120 frames per second and played it back in the standard 30 frames per second you would be seeing the footage at 25% of its original speed.
The trade-off with shooting in the high frames per second is that you are required to select a lower resolution to significantly increase the camera’s frames per second.
For the GoPro Hero 4 Black, Silver and Session models below are your Frame Rates and Quality options.
When shooting with a high frame rate, it is critical that you have adequate lighting because as more frames are taken every second, the exposure time gets shorter and the footage will appear darker.
As you can see from the chart above when you increase your frame rate there is a trade-off to quality. Thankfully GoPro Studio’s Flux feature helps to get around this problem.
Flux works by creating additional frames that are inserted between the frames taken during filming. Sounds a little complicated, right? Well let me break it down for you with an example:
If you filmed a scene at 30FPS and then during editing slowed it down by a third, this would mean that every second of footage would only contain 10 frames. If you played the video through at this speed it would look more like a flip book animation than a quality video. However, if you applied Flux to this footage the software would create 2 additional frames for every frame that was recorded. This means your end video would play back at one third of the original speed at a smooth 30FPS with no loss of quality.
To apply Flux, simply select the Video Controls while in the Edit tab. Then move the Speed control bar to the play back speed you desire. Whenever you move this control bar the Enable Flux tab will be checked automatically.
Flux can work with any quality of video including 4K, 2.7 K and HD. At first this may seem like the perfect solution to the Quality vs Play Back speed dilemma – you can have your cake and eat it too!
However, the Flux function has two major flaws. First of all, it can be an extremely lengthy process – after all, the GoPro studio needs to create the additional frames to insert between the ones you actually captured! The processing power required to do this can be quite time-consuming, and for this reason I recommend that you only apply Flux to very short sections of your footage.
The second drawback is that it is difficult to predict what the end product will look like using Flux. When applying it to a moving object, there can often be distortion around the object. The chances of distortion can be minimised by:
- Not filming too close to moving objects
- Filming with a simple and consistent background such as clear sky or still water
- Positioning the camera so that the moving object is travelling either towards or away from the camera, as opposed to across the field of view
- Filming with a high FPS rate. Although Flux does artificially increase the FPS rate, the fewer additional frames you require, the less likely it is that the image will be distorted. For example if you want to slow a video down to 5% and you filmed at 30FPS, the software would need to create 20 frames for every 1 frame of footage. However, if you shoot at 120FPS only 5 would need to be created per frame.
Slowdown in editing without Flux
The third way of using slowing down your footage is to slow it down using GoPro Studio without the use of the Flux setting. You can do this by unchecking the Flux option when adjusting the playback speed in the Edit tab. This will produce a slow motion video but the end result will be choppy (think the flip book animation effect mentioned above).
This method should only be used as a last resort, such as if your footage was shot with low FPS and Flux is causing distortion.
The most important things to do to ensure that that your slow motion videos turn out in the way you envision are:
- Record your footage at the highest fps available within the quality range you require
- If possible, position the camera so that the moving object is going towards or away from the camera with a clear, consistent background.
- If you need to slow the footage down while editing, apply Flux but limit this to short sections of your footage or prepare for a lengthy wait!