Jump to content


Photo

Alexa mini noise in the blacks

Alexa Mini Noise

  • Please log in to reply
5 replies to this topic

#1 Michael Ognisanti

Michael Ognisanti
  • Basic Members
  • PipPip
  • 35 posts
  • Cinematographer
  • Chicago

Posted 08 November 2018 - 10:09 AM

Hello,

 
I have a couple projects coming up where I will be shooting in dark environments.  One is a TVC of people against a dark gradient background and the other is a short film of night exteriors and interiors.  
 
I recently noticed some noise in the blacks when shooting with the Alexa Mini at 800 iso.  Has anyone else found this?
 
Are people rating this camera lower when shooting in dark settings to raise the shadow detail.  I’ve always done this with Sony but didn’t think it was necessary with Alexa as well.
 
Thanks for you help
Michael 
 

  • 0

#2 David McLeavy

David McLeavy
  • Basic Members
  • PipPip
  • 15 posts
  • Director

Posted 08 November 2018 - 10:48 AM

Are you seeing more noise in the blacks than in the image overall? The Alexa has some noise throughout the image but its generally a pleasing texture. Ive never seen heightened noise in the shadows at 800.
  • 0

#3 Michael Ognisanti

Michael Ognisanti
  • Basic Members
  • PipPip
  • 35 posts
  • Cinematographer
  • Chicago

Posted 08 November 2018 - 12:17 PM

Are you seeing more noise in the blacks than in the image overall? The Alexa has some noise throughout the image but its generally a pleasing texture. Ive never seen heightened noise in the shadows at 800.

Thanks for you response David

 

To my eye I see it more in the blacks but I might just be more sensitive to it.  I've used Sony a lot and that's always something I'm looking out for and rating the camera 1-2 stops slower.  I was just curious if people are doing the same for Alexa.


  • 0

#4 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 20300 posts
  • Cinematographer
  • Los Angeles

Posted 08 November 2018 - 02:25 PM

Noise is fine at 800 ISO if your blacks are normal for the display gamma.
  • 0

#5 Bruce Greene

Bruce Greene
  • Basic Members
  • PipPipPipPip
  • 635 posts
  • Cinematographer
  • Los Angeles

Posted 08 November 2018 - 06:36 PM

I'm now grading a film we shot on Alexa mini at ISO 800.  There were a few times when I wanted to present a really dark scene on set where I changed the ISO to 400 or 500 to insure I didn't go too far.

 

But, in the grading I'm finding a number of scenes where I've had to raise the exposure significantly and it's not too bad.  So far, I haven't reached for noise reduction.  Though, I do see some noise, it's not really bothering me ... yet :)

 

I think if you shoot at ISO 1200+, and underexpose, you're going to see some additional noise.  I had one scene on my previous show where I shot at ISO 1600 at night and went too far.  Noise reduction in post solved the issue but I would hate to need to use it on a significant portion of the movie.


  • 0

#6 David Mullen ASC

David Mullen ASC
  • Sustaining Members
  • 20300 posts
  • Cinematographer
  • Los Angeles

Posted 08 November 2018 - 06:42 PM

It all depends on how you light and color-correct your shadows.  If you get the exposure and look, the lighting ratio correct, then 800 ISO is fine for noise.  If you lift your shadows by a stop in post, you effectively rated the camera at 1600 ISO for the shadows, and obviously you'll get more noise.

 

This is one reason, assuming I have enough light, I'd rather "underexpose" the scene partly by lowering the ISO, so I might light and shoot a moonlight scene at 500 ISO.  It's just in case I have to bring anything up in post.  But I've also shot night work at 1280 or 1600 ISO on the Alexa because I had no choice, and the noise was fine, visible but acceptable.  But in those cases, I didn't expose on the dark side because I knew I had limited flexibility to color-correct the shadows.

 

If you're looking at the Alexa image in log, you're going to see more noise but the same thing is true if you look at a log scan of 500 ISO film stock.  The display gamma/contrast hides a lot of that once the blacks look black.


  • 1



rebotnix Technologies

Rig Wheels Passport

Metropolis Post

Visual Products

New Pro Video - New and Used Equipment

Wooden Camera

Abel Cine

CineTape

Tai Audio

Willys Widgets

Ritter Battery

Paralinx LLC

CineLab

Media Blackout - Custom Cables and AKS

Technodolly

Gamma Ray Digital Inc

The Slider

Glidecam

Aerial Filmworks

FJS International, LLC

Broadcast Solutions Inc

Technodolly

Paralinx LLC

CineTape

Willys Widgets

Glidecam

rebotnix Technologies

Abel Cine

The Slider

Aerial Filmworks

Gamma Ray Digital Inc

Tai Audio

Metropolis Post

Ritter Battery

Visual Products

New Pro Video - New and Used Equipment

CineLab

Broadcast Solutions Inc

FJS International, LLC

Rig Wheels Passport

Wooden Camera

Media Blackout - Custom Cables and AKS