8 bpc Effects in 32 bpc?

[Darby Edelen]

[Alex Kuzelicki] “Just say you have a project that you will ultimately render in 32bpc but you have a bunch of effects that are only 8bpc.”

Note: while the color information in your compositions may be 32bpc, the file you render out of AE will not be 32bpc, there are no codecs that support this. You will ultimately render to 8bpc (well… some codecs support 12bpc). 32bpc is beneficial not for what it gives you in the final render, but for what it allows you to do to get that final render.

Now, here’s the problem with using 8bpc effects:

The simplest way to put it is: calculations that After Effects makes while compositing are much more accurate and ‘natural’ in 32bpc.

When you use 8bpc effects in a 32bpc project you are introducing errors. The 8bpc effect can only generate 256 unique values per channel, if this effect is used in a 32bpc project it will still ‘work’ but you are sacrificing the accuracy that 32bpc allows you (significant digits anyone?).

In addition the values generated by any 8bpc effect will only range from 0-1 in the float (32bpc) realm, giving you no overbrights from these effects. You can, however, introduce overbrights by stretching the values out with, say, a Levels effect.

So the bottom line is, feel free to use 8bpc effects, but be very wary of how you do. If it looks alright in the comp window, I wouldn’t worry too much, what you see is usually what you get in the AE comp window.

Darby Edelen
DVD Menu Artist
Left Coast Digital
Aptos, CA

[Alex Kuzelicki]

Hey,

Thanks Darby.

I learned a lot from your post.

Cheers,

ALEX

[Solie Swan]

There is an effect preset call compander (I think) that will try and minimze the issue of using 8bit and 16bit effects in a 32bit timeline. While he does not deal with this issue you might want to look at Mark Christian’s book on AE7 which has a section on 32bit and somewhere on redgiantsoftware.com are video tutorials on elin which provided a 32bit workaround in AE6.5. Though dated I think they are still worth watching. Fianlly you might want to go over to prolost.blogspot.com and search around for a whole 32bit workflow for AE7.

[Alex Kuzelicki]

Hey,

Thanks Solie. Will check out those leads.

So much to learn, eh?

Cheers,

ALEX

[Darby Edelen]

Of worth noting is that you lose some precision using the HDR Compander/Expander effect, from Adobe’s Documentation:

“Because the first instance of the HDR Compander effect compresses the range of values through sampling, some precision is lost. For this reason, use the HDR Compander effect only if you