When I picked up my A7sII I was really excited to try out SLOG3 but when I did some tests I kept seeing banding in the highlights after applying a LUT, no matter what I tried.
I had expected it to be usable since Sony decided to add it, but it clearly is designed for a 10-bit or higher codec. The 8-bit codec breaks apart when you start grading it.
Initially I hoped that it had something to do with not using a LUT specifically designed for SLOG3, so I upgraded my Impulz LUTs to the 'Ultimate' Package (which includes the SLOG3 LUTs) and I ordered James Miller's set of Deluts for SLOG3.
When I applied those SLOG3 specific LUTs however, the problem still existed, under certain conditions you see some nasty banding in the highlights.
Finding a solution
I tried several things to find a solution for the banding problem:
- Use different ways of exposing, have the highlights anywhere between 100% and 70% zebras
- In post, using grain to hide it
- Changing Knee values in the SLOG3 picture profile
- Shoot in SLOG2, convert to SLOG3 with a LUT and then use the SLOG3 LUTs.
None of them worked.
The solution to avoid banding on the A7sII
Instead of shooting in SLOG2 or 3 I changed the Gamma settings to CINE4 and the color mode to S-Gamut3.Cine. To expose my images I set my zebras to 100% and higher and made sure none of the highlights clipped (I mention this because it is different to exposing with SLOG3, where I got the best results making sure highlights didn't clip at 77%).
By setting the gamma to Cine4 you will lose just a little bit of dynamic range (according to Cinema5D about half a stop) but you will also lose the banding.
The color mode I am using is exactly the same as shooting SLOG3 (with Picture Profile 8).
To make the image on the viewfinder and backscreen more pleasant to view and easier to focus you can still use the Gamma Display Assist by setting it to SLOG2 or SLOG3.
The only thing you need to do to be able to apply a LUT optimized for SLOG3 is changing the exposure of the footage in post before applying the LUT.
FCPX is my editor of choice and I add a color correction effect and change the following exposure settings:
- Global: +22%
- Shadows: +8%
- Midtones: +9%
- Highlights: -37%
I saved these settings to a color correction preset so I can use them over and over again.
These settings are by no means scientific or anything, play around with it as much as you like to get the result you want. The point is that you can get your Cine4 footage to look like SLOG3 footage to be able to apply one of the many great SLOG3 specific LUTs.
Start Update May 2016: Settings in DaVinci Resolve
- Offset 30.5 (translated from Global +22%)
- Lift 0.08 (translated from Shadows +8%)
- Gamma 0.09 (translated from +9% Midtones)
- Gain 0.63 (translated from -37% Highlights)
I have create a LUT that applies the correction as specified above:
Extract this file and place anywhere in the following folder (or subfolder):
- Library\Application Support\Blackmagic Design\DaVinci Resolve\LUT
Please remember that this is just a starting point, not all footage is shot with the same exposure, you will have to create a node between this LUT and the one that contains the grade (or look) and adjust the exposure in a way that suits the particular footage.
End Update May 2016
After the exposure correction my Cine4/S-Gamut3.Cine footage looks very similar to SLOG3 footage.
But ofcourse the best thing of all and the reason for writing this blog post: After applying any of my SLOG3 specific LUTs there is NO BANDING IN THE HIGHLIGHTS!
I have tried this using Impulz LUTs, Deluts, they all work and look almost exactly the same as the SLOG3 footage after applying the same LUT except for the fact that there is no banding visible.
The added benefit to shooting with the Cine4 gamma is that you no longer have to shoot at ISO1600 or higher but can start at ISO200.
The proof is in the pudding, here are examples of the same scene, under the same conditions, shooting SLOG3 and Cine4. I applied the Eastbrook LUT from James Miller's set of SLOG3/2 Deluts.
As you can see the difference is in banding is huge, and there only is a very slight difference between the two images in term of color and contrast (I think I even prefer the Cine4 version).
Below you can see the difference between real SLOG3 footage and Cine4 footage made to look like SLOG3 footage:
'Autumn' shot in SLOG3
Before this discovery I shot this video in SLOG3 and graded it with the 'Baxter' LUT from James Miller's set of Deluts:
Although the banding issue is not really visible in this video, I had some clips (that I didn't include) that really showed some nasty banding.