The Short Answer:
The question is, should I render a movie or an image sequence? The short answer is; png sequence. You can stop reading now and go ahead and render. While you're rendering, why not come back and read the rest?
The Long Answer:
Now don't get me wrong, there are plenty of times when I render from After Effects as a QuickTime movie or AVI, or even MP4 or WMV. Usually it's when my project is finished and I can bypass my final edit in Premiere. Just pushing out that final movie for the client. Other times I will render out a movie to be used in Premiere when I know the editor is not experienced enough to know how to deal with image sequences (especially if sound is involved). Or if I know that the piece will be used in a Final Cut 7 project. (Not sure about Final Cut X, but FCP7 can not directly imnport image sequences.) But there are several major downfalls with movies and avi's.
Disadvantages of Mov's and Avi's:
- Large file size; especially when dealing with uncompressed movies, and alpha channels
- Quality loss during compression; applies more to QuickTime, which uses the Animation codec to compress AE renders
- If there is a mistake, you must re-render the whole animation
Advantages of Image Sequences:
- Smaller file size
- 32-bits per channel capability
- zero quality loss
- easier to fix mistakes
- easier to net render
Those last two are huge points for me. Let's say that you render out your final animation to bring into your editing software. Now let's say your client needs a small change, or you find a mistake.
Did you render out a movie? Then you'll have to re-render your entire comp/scene. Depending on how complicated it is, this could add hours to your render time. You could render out that small chunk as its own small movie and then try splice it together in your editing program but... seriously?
Did you render an image sequence? Great! Then you'll only have to re-render the section that needs changed! Simply use the same name and your frames will be overwritten. If your NLE is smart enough (like Premiere) then your timeline will automatically update with your new frames, and you are good to go! You've saved a ton of time because you only had to render a small section of your work, rather than the whole thing. This will save you tons of time in 3D as well as AE.
It is getting easier and easier to build your own render farm for AE, Cinema 4D and other software. I am currently planning my own! All you need is a bunch of old computers, and you can set up a network render farm in minutes. If you are working at a larger production house, and are already using a render farm, then you already know exactly why you MUST render as an image sequence.
A render farm can only render image sequences. They can not render movies. A render farm works by passing off frames to multiple processors; each processor renders one frame at a time, and then passes that completed frame to a shared storage folder. So one computer renders one frame at a time.
It is simply not possible to render a movie this way. A movie can only be rendered by one machine. So if you are planning to save tons of render time with a render farm, better get used to handling those image sequences.
What kind of Image Sequence?
Alright, so now that I hate movies forever, what kind of image sequence should I render? PNG? JPEG? TIFF? TGA?
Most of the time, I will render to a PNG sequence. Although it technically is a lossy format, the compression is very good. It also supports alpha channel, and the file size is very low. This is my go-to format.
For times when I need a completely lossless format, or 32bpc, I tend to choose targa, but tiff would work just as well. In those cases, it mostly depends on what you will use to view the files. TGA files tend to be easier to work with. Client demands may also play a part here. For example, I recently rendered out an animated graphic to be used during a live broadcast and it HAD to be a targa sequence, simply because that's what the switcher could use. So special circumstances may dictate which file format is necessary.
I would advise against using jpeg ever, because it is a very lossy format, and may even show artifacts in the render. It also doesn't support alpha channel, so don't even bother. Choose PNG instead.
Again, I want to stress that there isn't any "right" answer. This is simply my own workflow and work habits. I would love to hear about your workflow, as well as any tips, suggestions etc in the comments below. Thanks for reading! Happy rendering!