I shot this video of swallows feeding at 4x slow motions. I want to include it in a longer video on this pond, first at regular speed and then again at slow motion on the theory that the regular speed goes by so quickly that people can best appreciate what is happening in slow motion. I'm concerned that viewers may not appreciate that it is the same scene in slow motion. The transition is a cross fade. Is there some better transition that will alert viewers that it's the same scene replayed.
https://youtu.be/dkT8ypLhmjE

can you start and end the clip at normal speed but ramp it down to slow motion in the middle so the viewers can see it's the same clip.

Thanks, Paul. It seems like a better transition. I'll use it

If it was me I wouldn't even use the normal speed version because your shutter speed was too fast and it doesn't look very good. Also, I can clearly see the focus going in and out. If you only use the slow-motion version the shutter speed looks more correct and you may be able to cut around the out of focus parts.

Were you using AF? What was your shutter speed and frame rate?

This was shot with a Nikon D850. Frame rate was 29.97 (30 on the Nikon Menu), Shutter speed of 250 for 4X slow motion (As close as you can come to 240.) Auto focus was on. Thanks for the suggestion.

Yeah, you never want to use AF for wildlife . . . and almost nothing else either when shooting video because it will screw you over more often than it works. Also, as you're seeing, the same shutter speed cannot be good for slow-mo and normal speed at the same time. You must pick one or the other before you press the record button. Because if the shutter speed is correct for one, it cannot be correct for the other. Either there will be too much motion blur or not enough.

As to motion blur, I thought that twice the frame rate (120 in this case) was a good rule for motion blur. Was I wrong?

How would you suggest focusing on rapidly moving swallows when you don't know when and where they will appear, and are then gone in a few seconds?

I shot this in slow mo, and then sped the video up to regular speed in Premiere Pro. My goal in changing the speed was to convey first to the viewer how rapidly these birds move and then to give the viewer a chance to see the activity at a comprehensible speed. Showing the sequence in slo mo was not consistent with my artistic intention. How would you suggest going from regular speed to slow motion or back when shooting rapidly moving birds like swallows?

This seemed an impossible situation that I wanted to make the best of, but I'm really willing to learn if there was some other way to approach it.

When you said you are shooting at 4x slow-motion I assume that means (4 x 30 fps) 120 frames per second. And as you said, you were shooting at 1/250. That is the right shutter speed for that frame rate.

But when you try to convert that footage in post to normal speed (30 fps) now you have 30P footage that was shot with a shutter speed of 1/250 and that is NOT correct. That is too fast and doesn't allow enough motion blur so you get a very choppy, staccato kind of look. In my opinion, that is an awful look and you'd never see it in a high-end wildlife documentary.

If you want to illustrate both types of action (slow and normal) then what you need to do is shoot two separate shots:
1) 120 fps @ 1/250
2) 30 fps @ 1/60 or 1/80

There is no way around shooting two separate shots for getting normal and slow-motion clips that each have the correct amount of motion blur.