A7sii slog3 avoid banding (especially in skies)

llirik said:
For now, I'm going to stick with shooting in slog2 as I have more experience and it does seem a bit more forgiving.

I HAVE noticed an improvement with slog3 in one particular instance: it helps greatly to keep away blown out windows. In SLOG2, i needed to always be mindful and expose just barely to keep detail outside the windows, but still have good exposure inside the vehicles. SLOG3 definitely increases the DR in this instance.

But the AWB issue is terrible. I didn't notice it on my a7r2... just the a7s2.

Here's how the video turned out. Not terribly happy with all the issues I had to contend with image wise compared to my previous a7s + shogun setup... but it DID allow me to get unique angles due to the small size and weight.

Click to expand...

Why would you use Auto White Balance?
 
I used it here. Because I was running around and shooting with available lighting in wildly varying conditions, and had no time to adjust it for every take. It worked reasonably OK, but I didn't need it to be perfect anyway, just in the right ballpark. Crucially, I didn't get any mid-take changes (not sure if by luck or because of a different implementation in the RX100 IV than in the a7S II). I did get some undesired changes between adjacent takes: shoot a wide shot, then change to a portrait shot and the AWB may change.
 
Any chance i could see the original camera files for the skies? Am curious in YUV mode to see what's there. The guy on eoshd saw similar issues but the files provided for download are not camera originals.

Slog3 is like a pencil without lead on this camera (pointless). As the camera cannot fill the bucket resulting in wasted space and leading to lack of tonality.

I don't think you should be seeing more range in Slog3 either. What you might be seeing is with Slog2 your post application is clipping whites, in PPro for example (with the current version) you need to bring the highlights down but not with Lumetri, you need another colour correction effect on the timeline to do this. Slog3 may look like more range because the highlights are lower then this clipping won't be seen.

cheers
Paul
 
(he said he's seeing more range not in the highlights, but in the shadows, because noise and compression don't eat them as much)
 
Samuel H said:
(he said he's seeing more range not in the highlights, but in the shadows, because noise and compression don't eat them as much)
Click to expand...

I was meaning the comment about SLog3 keeping windows from blowing out, i just assumed that meant different highlight handling.

The Slog3 shadows are raised much higher than Slog2, in my own tests i actually thought by the time you equalised them Slog3 was noiser down there, but i didn't see more range

Hopefully this weekend i'll get a chance to write up properly

cheers
Paul
 
What I understood is that both clip the highlights exactly the same, but since the shadows are eaten by noise+compression on slog2 to a larger extent, he has to expose it higher than slog3 and keeping highights alive becomes an issue.
 
I asked if he means exposing slog3 lower, and he said yes.
I personally think that I prefer using slog3 for grading because of the more gentle shadow curve, but prefer slog2 for recording with less banding. So my solution is really to record in slog2 sgamut3cine, and use a slog2 to slog3 lut, then grade as slog3. Get the best of both world.
 
Samuel H said:
I used it here. Because I was running around and shooting with available lighting in wildly varying conditions, and had no time to adjust it for every take. It worked reasonably OK, but I didn't need it to be perfect anyway, just in the right ballpark. Crucially, I didn't get any mid-take changes (not sure if by luck or because of a different implementation in the RX100 IV than in the a7S II). I did get some undesired changes between adjacent takes: shoot a wide shot, then change to a portrait shot and the AWB may change.
Click to expand...

Wouldn't a simple daylight balance work (especially considering that the conditions were wildly varying)?
At least the balance will be more consistent, plus there's plenty of white elements in the shots that may help to fine tuning if needed.

Anyway, I personally find awb a bad choice and I always end up having more hassle than benefits using it.
Luckily custom setup is very fast to set up, and in case these are very small and portable: http://is.gd/p8aM7r
 
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^ My usual way of doing this in these situations is: before I start shooting, I use a gray card to get custom white balance presets for sunlit areas, shade areas, and indoor areas. Then, before every take, I select the one that fits.
The problem with that is that all 3 presets start to get not-so-accurate as the day goes on, which means lots of small deviations have to be fixed in post, plus I sometimes forget to choose the right one, which means a few huge deviations have to be fixed in post.
This time I wanted to see how AWB would do. It wasn't an important project anyway. My conclusion: it's not much worse than what I get when I do it all by hand (just as many small deviations, just a couple of big deviations), and it frees my attention so I can concentrate on other stuff instead. I'll use this more often on this kind of projects.
 
bump...

It seems the best practice would be to shoot Log-2 and record external to get 4:2:2 and a higher bitrate, but always keeping in mind that you are getting 8-bit bitdeph so when you have smooth gradient you should try to expose that portion of the shot so that it doesn't have to be pushed too much in post aggravating the issue.

If the HDMI output was 10-bit this camera would be an all around killer... I am happy with everything else I see, but the 8-bit banding is scary.
 
I found frames with different white balance (green/magenta random changes) scattered around while editing A7SII 4K footage in FCPX.
They completely disappear when I transcode to "optimized" (ProRes 422) media. So in my case, I have a feeling it's a compression problem.
 
Something similar has happened to me when using auto WB: the camera can change it for a few frames while rolling, and then back. Very dangerous.
 
llirik said:
Another issue I'm finding... is white balance shift in between frames... i.e., in the same shot. Would that be the AWB messing up? I haven't had the issue before on the a7s, so not sure if it could be something else.

View attachment 107179View attachment 107180
Click to expand...

The A7S occasionally did this to my footage (and stills in rapid fire mode).

You can especially see it if you point at a black object in Slog2 or 3 & quickly switch back & forth between shutter speeds in M mode. I see it in the A7SII as well, but not as much. Once you hit record it goes away almost entirely (but creeps up when you least expect it).

See my thread here:
http://www.dvxuser.com/V6/showthread.php?330928-A7S-Color-Flicker

EDIT: I never shoot AWB...this happens to me with locked color temps
 
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