Arri Alexa Mini Digital Dust, Cosmic Radiation and Yoga

mahadevan

mahadevan

Member
Hey All,

I just finished shooting a series of yoga workouts on a black background with the Alexa Mini (2 Camera Shoot). About a month after shooting, the editor noticed a number of white specks throughout the footage (both A and B camera). The white specks would randomly appear in a one frame and disappear in the next (no consistency to area of frame). After speaking with Arri, they believe that this is an environmental issue caused by cosmic radiation. We've currently found about 15 specks within 3 episodes of shooting (which were shot on 3 different days). See below for a couple of samples with the specks. Let me know if you've seen anything like this before. We're going to be shooting the next round in a week and are trying to prevent this issue.

Best,

Chad Mahadevan

Screen Shot 2018-11-30 at 1.00.15 PM.jpgScreen Shot 2018-11-30 at 12.55.52 PM.jpgMicki - 6.jpgScreen Shot 2018-11-30 at 1.00.15 PM.jpgScreen Shot 2018-11-30 at 12.55.52 PM.jpgMicki - 6.jpg
 
This is something that comes with the territory.

I've seen it on multiple Alexa cameras AND on other cameras like the Blackmagic Ursa Mini Pro.

I've heard the same explanation from Arri.

I would say that it almost always seems to be when shooting on ProRes. I doubt there's anything you can do about cosmic radiation hits if that's indeed what causes this.

JB
 
That's weird, I've never heard of or experienced such a thing, "cosmic radiation" affecting picture? Really? Next one, shoot it in another dimension?
Looks like it wouldn't be that hard to fix in AE or even FCP X or Premiere, just a PITA to do so, I am sure.
 
puredrifting said:
That's weird, I've never heard of or experienced such a thing, "cosmic radiation" affecting picture? Really? Next one, shoot it in another dimension?
Looks like it wouldn't be that hard to fix in AE or even FCP X or Premiere, just a PITA to do so, I am sure.
Click to expand...

I actually used to hear something similar thrown around back in the day(90's) about it effecting the chips in our old Betacams when they were in the cargo holds of planes flying around. Maybe CCD's were more susceptible or maybe someone just made it up to make an excuse for lit pixels, but regardless, it's not the first time I've heard something like that.
 
It's real though these apps take a while to "catch one":
https://crayfis.io/
http://cosmicrayapp.com/

In all the years of shooting with a variety of cameras, haven't noticed anything that got me thinking about cosmic ray noise. Perhaps the design of the Alexa's ALEV III sensor makes it more vulnerable and/or their firmware doesn't mask the issue as well as other cameras (e.g. as a side effect of in-camera noise reduction).

The example noise shown in this thread isn't that hard to remove using 'cloning'. There's also plugins which do this, and of course AE: https://nofilmschool.com/2010/06/how-to-remove-stuck-pixels-from-video-footage

See also:

https://forums.adobe.com/thread/2269873

Resolve: https://www.premiumbeat.com/blog/resolve-15-dirt-repair-dust-buster/
 
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(Update) I have recently tested (2) different Alexa Minis in a separate location and have had the same issues.
 
Can't say I've ever seen this in more than 20 years of working with CCD and CMOS imagers, certainly never with vacuum tube imagers.
 
Hey Paul,

Not too close, we're in Van Nuys. I also did this test in our Santa Monica stage and had the same results. Thanks.

- Chad
 
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