January 21, 2016 at 5:42AM

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How to handle with variable frame rates?

Hi there fellows!
Hi have some doubts:
I shoot some weddings and as you know people are sensitive to slow motion. I shoot with a dslr that can shoot 720 @60 or 1080 @30 tops. I know that 60fps is not ideal for slow motion but that is another question.
I have some questions regarding shooting and editing with different frame rates.
Should i shoot everything with a higher frame rate and then when editing apply some slow motion?
When editing should i have different sequences with different frame rates or have one single sequence and then work all the files in the same sequence.
Honestly i don´t even know where to star with this questions. Is a bit confusing to me all this numbers..
Thanks!

1 Comment

There's a lot to say on this subject, but here are some basic principles.

First and foremost, there's never a do-over for a wedding. Whatever your creative ambitions, you have to make certain that you have the fundamental coverage to do right by the event. If somebody else is doing principal photography and you are just contributing some extra flair, that's OK, but if capturing the wedding is your job, don't make the mistake of reaching for something beyond your grasp, technically, creatively, or both.

Secondly, the question of frame rate cannot be divorced from the question of shutter angle. In general, shutter angle is 180 degrees, meaning that if you shoot at a 30fps frame rate, your shutter is open for half that time, or 1/60th of a second. When you shoot 60 fps, the "normal" shutter would be 1/120th of a second. It doesn't look terribly wrong when you slow 60fps down to 30fps for a slow-mo effect with a 1/120th of a second shutter speed, but if you try to conform 60fps to a 30fps timeline (dropping ever other frame) to make the footage play at normal speed, you get something that plays at normal speed, but which also looks jittery because the 1/120th of a second shutter speed is effectively a 90 degree shutter angle. Typically weddings are about elegance, beauty, grace, etc., and thus shooting at high frame rates and conforming down work against that. Strongly.

You can attempt to address this problem if your camera lets you shoot with a 360 degree shutter. In that case, 60fps @ 1/60th of a second can be conformed to 30fps (playing every other frame) @ 1/60th of a second, which will look perfectly normal. However, when you play your 60fps footage at half speed (30 fps, playing every frame) you will have 2x more motion blur than "normal". That actually might look good, or it might look excessive. If you like the look, shoot 60fps at 1/60th of a second and call it good. If you don't have one camera for regular speed and one for slow-mo.

One other consideration is that most DLSRs have a very limited bitrate when recording. It might be 25mb/s, or 50mb/s, or 100mb/s. Whatever the limit, if you shoot at 60fps and conform to 30fps (throwing away every other frame), you are effectively shooting with 1/2 the bit rate you would get when shooting at 30fps. To do this the camera will be compressing your data more heavily, giving you less accurate colors, less forgiving tonal range, etc. This can also be a problem for a wedding, where brides tend to wear white (which has many subtle shades) and grooms tend to wear black (which has many subtle shades). Again, you should test whether your camera looks good enough when using only half its effective bitrate.

Finally, there does exist software that can help produce a slow-mo effect by creating "in-between" frames. Such software works best when there's no motion blur. You can dial in a very short shutter speed to kill motion blur, but again, that's going to make your normal 30fps footage look very jittery--not the best look for "normal" wedding footage.

Lots of these caveats can go away if you have higher-end equipment. A RED DRAGON camera (which, when ready to shoot, costs $40K) can shoot high-res, high-frame rate footage with tons of data per frame, making it easy to pull stills from video, enhanced slow-mo footage, and good-looking regular footage. The new RED RAVEN does all of this, albeit with 4K instead of 6K resolution, but at a revolutionary price of under $10K (ready-to-shoot). I'm not suggesting you absolutely need this for what you are doing, but pointing out that these are tools that have the capabilities to go beyond the typical tradeoffs one must make in the DSLR world.

Bottom line: only try to do more than your equipment can reasonably handle if you can afford to throw it away as a learning experience.

January 21, 2016 at 7:58AM

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