As an animator producing. mp4 files, you don’t have control over the final file size, except by modification of the width and depth of the video image.
By using a utility like Handbrake you can modify, the dimensions of the video, the number of frames per second, the image and sound quality.
I had a recent project that was 680K bytes, when output from Pencil2D and after several attempts this was reduced to 280k bytes and the overall quality was only reduced slightly.
Optimization of the file size affects the space required, say on a website and the load time. The latter is particularly important when the video is downloaded over mobile Internet connection.
Handbrake is a dedicated video transcoding application. The focus of Pencil2D is on animation so it will inherently have a lot less options for video exports. The default export options have been selected to produce visually lossless encoding with reasonable file sizes and the widest possible device compatibility. If you are looking for more control over the export process, I recommend you export as a png image sequence and encode that using ffmpeg or a video editor with the options you want.
The situation I was in was, I required to produce a variety of different animations, to meet the objective. But I didn’t have the resources to produce the different drawn backgrounds required. The different backgrounds was essentially the difference.
The easiest way to produce them, was simply to take a photograph and use that. I experimented with editing the image, using Gimp to adjust the colour depth. But this did little to reduce the file size.
If I’d drawn the background image, in traditional cartoon style this would have had the desired effect.
Thanks for your helpful comments, you’ve provided food for tbough, for future projects.
What I always do is export at full size first, and then use an online video converter to adjust those properties. I use this exact site: Online video converter to MP4
I always downscale my animations in both video resolution and audio bitrate to assist in getting a more old-TV-recorded look to my projects. I’m investing in a VCR player though, to further help with that effect.