original files vs. a rendered file
The first thing to keep in mind is that sending the original footage is sometimes not optional, depending on the project.
Using the original files or a render can both be very beneficial or make life very complicated. Which one is true varies per project and there is no one-size-fits-all solution.
This page gives you a generic pros and cons list, but every project would ideally be analysed by a professional before this decision is made.
Sending a ProRes or DNxHD/HR file:
If you shot compressed video (like log footage in XAVC, ProRes or DNxHD/HR), then a 10-bit codec such as ProRes422 HQ or DNxHD 185x is usually enough.
If your original footage is 444, then you can make a ProRes 4444 (or another 10-bit 444 codec) file and still retain the quality.
Higher flavors of ProRes are usually overkill for most cameras, generating big files. But further not a problem.
If you shoot compressed (not RAW) using ARRI cameras, you have to disable the built-in LUT which comes in each video file before making the export for color. You can do that easily in the editing software.
Using the original files:
If you shoot RAW formats (like RED, ARRI or Blackmagic RAW), you can’t make an export without losing important color data. In that case we need the originals. It can be a bit inconvenient, but it may offer more flexibility/quality in grading.
If you shoot compressed (not RAW) using Arri cameras AND using an embedded (NOT burned into the footage) LUT, then we can only access that LUT during grading if we receive the original camera files.
How to decide in case of ARRI footage:
As you see above, with compressed ARRI video, you have the option of either a render or original files.
The easiest way to decide whether to send a ProRes file or the originals, is by asking yourself (or the DP) if the colorist should take the embedded LUT into account.
If that LUT is an important part of building the look, then it’s better to send the originals.
If you believe the colorist will be fine building his own look based on your briefing, then disable the LUT in Avid/Premiere/FCP and send us a ProRes file.