Hello and welcome. This article does not cover how to make deforum videos so if you haven't already figured that out save this one for later. This goes over some other methods like how to make them slow-mo, add interpolated frames which can smooth them out, and upscale which makes them look better.
First thing you need after you've made your video is Flowframes, it's free (unless you want to pay), get it here: https://nmkd.itch.io/flowframes
Install using whatever it recommends for your system.
Select your video and where you want it saved then select how many interpolated frames you want it to add and if you want to be slowed down at all. Click Interpolate! and let it run until it's finished.
Play around with the settings to find what works best for you and your style. 10x means it's adding 10x the amount of frames in-between each frame. 8x Slowmo means it's slowing down the frame rate after that 8 times. So if you have a 30fps video and you add 10x interpolated frames that gives you a 300 fps output. Slowed down 8x gives you 37.5 fps.
Now that you've done that it's time to upscale. You have a lot of options on how to do this, I believe there is even an option to do it inside the deforum extension itself but I've never tried it. I use Topaz Video AI. It's not free like Flowframes. It allows you to upscale 2 - 4 x and it's extremely easy.
Now you have a deforum video that may be slowed down, has interpolated frames, and is upscaled. Cool! But I bet it's massive in size. That's okay. Now we will convert the file. You can convert a 30gb .mov file down to a 1gb .mp4 file using compression. There are numerous ways to do this but I'll show you how I do it. I use Wondershare video converter.
Here all I've done is select I want to convert it to .mp4 and hit convert. Let it do it's thing then it's finished.
There is some tradeoff in quality here however. The converted .mp4 is not going to be as high quality as the original .mov. You have to decide what's more important. Hard drive space or quality. The difference is subtle but noticeable enough if you zoom in especially on the aliasing of the edges.
And there you have it. Have fun :)