ARRI DigitalGeneral CategoryGeneral DiscussionAlexa plus shows green cast over period of time
Pages: [1]
Print
Author Topic: Alexa plus shows green cast over period of time  (Read 1900 times)
gbalaji
Full Member
***
Posts: 100


WWW
« on: December 24, 2011, 11:41:58 PM »

We are shooting with Alexa Plus with Sup.5.

Over a period of time say after 6 hours of a day shoot, the camera shows green casting in the output. Is it to do with  long period of time of camera running or todo with anything else. We are using ND filters, if ND filters are issue it looks good for first 5 to 6 hours. We are using same lights for entire shoot.
Logged

Thanks
G.Balaji
Digital Cinema Designer / Evangelist
DIT,File based workflow & Post Supervisor fo

Guenter N.
Administrator
Sr. Member
*****
Posts: 360



« Reply #1 on: December 25, 2011, 08:59:09 AM »

There should be no change in camera since the sensor temperature is kept constant at all times but maybe something might be happening with your monitor after 6 hours?
or it could very well be one of your ND's.
If you lay all the ND's on a white paper - you should be able to immediately see if the ND's are matching or that there is a color shift in some of them.
Logged

Guenter Noesner
Technical Sales,
ARRI Inc. NY

gbalaji
Full Member
***
Posts: 100


WWW
« Reply #2 on: December 25, 2011, 07:40:01 PM »

Even I can say the change in Color temp or cast happens in my laptop when checking at end of the day
Logged

Thanks
G.Balaji
Digital Cinema Designer / Evangelist
DIT,File based workflow & Post Supervisor fo

Guenter N.
Administrator
Sr. Member
*****
Posts: 360



« Reply #3 on: December 27, 2011, 06:14:40 AM »

1.) What light source are you talking about?
 2.) Did you check your ND's?
Logged

Guenter Noesner
Technical Sales,
ARRI Inc. NY

Michael Borenstein
Digital Service Manager, Arri Inc.
Administrator
Hero Member
*****
Posts: 821



« Reply #4 on: December 27, 2011, 08:55:23 AM »

G.

Can you send me the log files and two dpx frame grabs as examples.

I'm at mborenstein@arri.com

Regards
Mike
Logged

Michael Borenstein
Digital Service Manager, Arri Inc.

gbalaji
Full Member
***
Posts: 100


WWW
« Reply #5 on: December 28, 2011, 07:13:32 AM »

Since the project is under NDA can't send you images.

But find it that when I try to decode Log files using ACES Color Space in Davinci Resolve, the cast is obvious too much than what I see on monitors on Set.

Is there anything to do with ACES Color Space encoding for ALEXA / REC 709 settings in Davinci Resolve
Logged

Thanks
G.Balaji
Digital Cinema Designer / Evangelist
DIT,File based workflow & Post Supervisor fo

Michael Borenstein
Digital Service Manager, Arri Inc.
Administrator
Hero Member
*****
Posts: 821



« Reply #6 on: December 28, 2011, 08:43:03 AM »

I'll have to check on the ACES workflow in resolve.  We might have some helpful info.  Are you only seeing this green cast when you decode from LogC to ACES?  That could be the issue.  What happens when you go from Loc to Rec709?

Thanks
Mike
Logged

Michael Borenstein
Digital Service Manager, Arri Inc.

gbalaji
Full Member
***
Posts: 100


WWW
« Reply #7 on: December 29, 2011, 09:06:51 PM »

Michael,

Got permission from DOP. Will send you frames to your email address. Could you provide your email ID
Logged

Thanks
G.Balaji
Digital Cinema Designer / Evangelist
DIT,File based workflow & Post Supervisor fo

Michael Borenstein
Digital Service Manager, Arri Inc.
Administrator
Hero Member
*****
Posts: 821



« Reply #8 on: January 03, 2012, 09:08:43 AM »

G,

Sorry for the delayed response due to the holidays.  You can reach me at mborenstein@arri.com

Hope all is well and you had a happy new year!

Mike
Logged

Michael Borenstein
Digital Service Manager, Arri Inc.

gbalaji
Full Member
***
Posts: 100


WWW
« Reply #9 on: January 09, 2012, 04:43:02 AM »

Check your email. Sent attachment of ACES / YRGB workflow rendered images for your testing.
Logged

Thanks
G.Balaji
Digital Cinema Designer / Evangelist
DIT,File based workflow & Post Supervisor fo

Michael Borenstein
Digital Service Manager, Arri Inc.
Administrator
Hero Member
*****
Posts: 821



« Reply #10 on: January 09, 2012, 09:35:19 AM »

Check your email. Sent attachment of ACES / YRGB workflow rendered images for your testing.

Just got it.  I will take a look at it and get our image engineer involved as well.  Please give me a few days together back to you.

Rgard,
Mike
Logged

Michael Borenstein
Digital Service Manager, Arri Inc.

DITDANE
Newbie
*
Posts: 27



« Reply #11 on: January 21, 2012, 07:08:21 PM »

I recommend balancing the RGB channels using a 18% card which should allow you to be at "home". Then work your look in. That should at least tell you where your at NDs, IRs, what ever filtration is in the box.

best,

-
dane
Logged

Dane Brehm
ICGDIT

Jamie Metzger
Jr. Member
**
Posts: 72

Logarythym & Blues


« Reply #12 on: January 21, 2012, 10:15:42 PM »

Also, feel free to "dial" out some green using the white balance feature. I have to use this all the time on a 2 camera alexa show. When we have an additional body, it's usually a PLUS and for some reason, the image is 3 points more green than the regular alexa's. Easy fix with the white balance tool.
Logged

Pages: [1]
Print
Jump to: