LUTs, ACES, questions...

Mindmatter wrote on 12/26/2018, 9:01 AM

Hi all,

as a new FS7 owner, I'm trying to get my head around working with SLOG3 and LUTs, and I want to make sure I understand certain concepts right.

I shot some test footage in SLOG3, and played around with different workflows in v16. I downloaded some LUTs from Alistair Chapmans site for the FS7 and had a look at a few ACES workflow tutorials.

So, what I'm wondering so far is:

1 - is there an advantage working in ACES over working with LUTs? It definitely seems top tax the CPU quite a bit more.

2 - why is it that most LUTs still need quite a bit of additional contrast adjustments? I used to think a LUT encompassed several parameters next to merely remapping / correcting the colorspace, such as saturation and contrast etc?

Using only FX correction, I need to bump up satruration in Color Fast 2 to a rather unhealthy level to get good results.

In the screenshots below, there's the naked SLOG3 pic, then with a LUT, then with a LUT plus Vegas color curves. Obviously the 3rd one is my favorite...just wondering why the LUT didn't take care of the additional parameters, or do I misunderstand the concept?

Thanks for any hints!

Comments

Marco. wrote on 12/26/2018, 10:32 AM

How do your project settings look like and which color space did you define for the clip properties?

Mindmatter wrote on 12/26/2018, 10:48 AM

Hi Marco,

when working with LUTs, settings are as usual, except I use 32 bit video levels as I import the FS7's 10 bit 4.2.2. footage. For the ACES workflow I set media properties / color space to the corresponding setting, in this case Sony Slog3 Sgamut3 cine and the project to full range ACES CC.

The strange thing is I seem to notice quite a bit more banding than usual when trying out LUTs. Is that normal in 10 bit?

Marco. wrote on 12/29/2018, 2:21 PM

I don't think using 10 bit should introduce any more banding than 8 bit, it should be vice versa.

Any chance to share a small sample clip of such FS7 10 bit footage shot in S-LOG3 mode?

Musicvid wrote on 12/29/2018, 10:04 PM

The strange thing is I seem to notice quite a bit more banding than usual when trying out LUTs. Is that normal in 10 bit?

Show us how a blue ramp target looks on a vectorscope and histogram. They will tell all, if it is truly banding you are seeing.

Mindmatter wrote on 12/30/2018, 11:38 AM

OK so it seems like I found a reason for the banding.

When applying Color Curves before the LUT filter, there is quite an amount of banding, most visible on the dark blue bottle in the background. ( pic 1 )

When putting it after the LUT, there's as good as none. ( pic2 )