Helium Strange Artifacts

[Steven Dean]

Seeing some strange artifacts in this recent product setup. As I was adjusting the lighting, and beginning to flag off the background further, I noticed this.

*Note - the still, and Vimeo video below, are boosted to ISO 2000 in order for this to be seen easier, but this was shot, and can be seen at 800.

R3D single frame: https://drive.google.com/file/d/1lyhK94tdU8IZ7FsW23QCdsjMUFtcEib9/view?usp=sharing

R3D 7.5 seconds (2.05 GB): https://drive.google.com/file/d/12sHR0MmVzzkYg2EylOXFbHa49j1JV8m6/view?usp=sharing


I don’t believe that I have ever seen this, in 9 years of RED ownership. I’ve seen banding when an image is underexposed, and then pushed, but that is not the case here. I understand that this is a high contrast setup, but I can’t accept that this is something “normal.” When the backdrop is held in front of the drive, the artifacts are no longer seen, so it seems to have something to do with the contrast of the image. I have definitely shot in high contrast scenarios before, maybe not exactly like this, but very similar. Completely crushing the black level could possibly remedy this, but that is not a practice that I do if I can avoid it. I like some “detail” in the black range.



Gear Used:

Weapon Helium, 50mm Summilux M, STH OLPF, 2 Joker 800 HMI’s

Shot at 800 ISO




Things that I tried to remedy (none worked):

Switched to LED lighting

Swapped Lenses

Blackshade

Switch OLPF

Full Camera Reset

Firmware update






Wasn't seeing this on the FS7 that was also in the studio. Does anyone have any insights?


Thanks!

 

[Bob Gundu]

This looks like the dreaded sensor smear.

https://www.reduser.net/forum/showthread.php?163665-Helium-Sensor-Smearing

 

[Steven Dean]

Thanks Bob, very useful discussion! I might vaguely remember this now, but it's been a bit. Cheers!

 

[Aaron Lochert]

Yup that looks familiar. Good 'ol CMOS smear. For what it's worth, I'd say your exposure is a bit bright by default, but processed at ISO 400 which puts the middle grey chip at 33% (in log) where it should be, it pushes your noise floor down and the smear is far less noticeable. And if you grade it with a black point adjustment to put black at actual black, it pretty much eliminates it. The thing to look out for is if your background was a dark grey, it might rear its head and you can't really fix that much without overly crushing shadows.

IPP2 - BT.1886 Medium/Medium