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Color Charts for Mars

Noel Sterrett
 

No need to pack your color charts for a shoot on Mars. A few are already there: https://mars.nasa.gov/embed/25619/

Anyone know what sensor/color science they use?

Noel Sterrett
Admit One Pictures

Mark Weingartner, ASC
 

And we all know the old joke…     How do you find out if there is life on Mars? Ask any video engineer:

   Put a chip chart up and if there is life on Mars it will walk between the camera and the chart.

Weingartner
Lost Angeles

On 27Feb, 2021, at 12:08 05PM, Noel Sterrett <noel@...> wrote:

No need to pack your color charts for a shoot on Mars. A few are already there: https://mars.nasa.gov/embed/25619/

Anyone know what sensor/color science they use?

Noel Sterrett
Admit One Pictures

Daniel Rozsnyó
 

Here is a more descriptive article about the referred color calibration device, you may find hardware details there as well - its a 1600x1200 Kodak CCD (KAI-2020CM), with a set of 11 filters on a wheel - including ND filters, the sensor is color, with Bayer CFA.


Check also the material on end of page, eg this paper:


Ing. Daniel Rozsnyo
camera developer
Prague, Czech Republic



On 27 Feb 2021, at 21:08, Noel Sterrett <noel@...> wrote:

No need to pack your color charts for a shoot on Mars. A few are already there: https://mars.nasa.gov/embed/25619/

Anyone know what sensor/color science they use?

Noel Sterrett
Admit One Pictures

Noel Sterrett
 

Thanks, great sites. Makes my chart knowledge seem totally inadequate.

Maybe we should to move to using charts with only 3 or 4 colors? That's all NASA seems to need.


On 2/28/21 2:47 PM, Daniel Rozsnyó wrote:
Here is a more descriptive article about the referred color calibration device, you may find hardware details there as well - its a 1600x1200 Kodak CCD (KAI-2020CM), with a set of 11 filters on a wheel - including ND filters, the sensor is color, with Bayer CFA.


Check also the material on end of page, eg this paper:


Ing. Daniel Rozsnyo
camera developer
Prague, Czech Republic



On 27 Feb 2021, at 21:08, Noel Sterrett <noel@...> wrote:

No need to pack your color charts for a shoot on Mars. A few are already there: https://mars.nasa.gov/embed/25619/

Anyone know what sensor/color science they use?

Noel Sterrett
Admit One Pictures


John Brawley
 

A grey card seemed to work well for a long time….

John Brawley ACS
Cinematographer
Los Angeles


On Feb 28, 2021, at 1:10 PM, Noel Sterrett <noel@...> wrote:

Thanks, great sites. Makes my chart knowledge seem totally inadequate.

Maybe we should to move to using charts with only 3 or 4 colors? That's all NASA seems to need.
Noel Sterrett
 

Still does.

On 2/28/21 4:35 PM, John Brawley wrote:
A grey card seemed to work well for a long time….

John Brawley ACS
Cinematographer
Los Angeles


On Feb 28, 2021, at 1:10 PM, Noel Sterrett <noel@...> wrote:

Thanks, great sites. Makes my chart knowledge seem totally inadequate.

Maybe we should to move to using charts with only 3 or 4 colors? That's all NASA seems to need.
Mitch Gross
 

While a grey card is a great tool, there is something to be said for a chart also displaying either red/green/blue or yellow/cyan/magenta. (Note the ‘also’ as a white/grey neutral reference is always worthwhile.)

As pretty much all of us work with RGB sensors (Bayer or otherwise), a three color chart can tell you how well each channel is saturating, getting polluted from a separate color, is performing in dynamic range, is performing in sensitivity, is showing noise, is clipping, etc. If the levels are particularly off, the way the image is processed can be adjusted to help compensate. For us old fogies, it can be like cooking the bath at the lab or maybe fogging the neg. 

Mitch Gross
New York

On Feb 28, 2021, at 4:36 PM, John Brawley <john@...> wrote:

A grey card seemed to work well for a long time….

John Brawley ACS
Cinematographer
Los Angeles


On Feb 28, 2021, at 1:10 PM, Noel Sterrett <noel@...> wrote:

Thanks, great sites. Makes my chart knowledge seem totally inadequate.

Maybe we should to move to using charts with only 3 or 4 colors? That's all NASA seems to need.
Adam Wilt
 

The Mastcam-Z is a stereo multispectral camera system (references in increasing order of geekiness):




Cheers,
Adam Wilt
technical services
Vancouver WA USA (no, not that Vancouver, the other one)
Noel Sterrett
 

Anyone know if it sends RAW back, or de-Bayer/process first?

On 2/28/21 5:25 PM, Adam Wilt wrote:
The Mastcam-Z is a stereo multispectral camera system (references in increasing order of geekiness):




Cheers,
Adam Wilt
technical services
Vancouver WA USA (no, not that Vancouver, the other one)
Art Adams
 

>>>A grey card seemed to work well for a long time….

 

That’s because film has the color science baked in. If you print the gray card as neutral then everything else falls in line (depending on the processing, of course, and even then I don’t think you could seriously skew the color short of cross processing or doing something very strange).

 

Digital is completely different. There’s a lot of math going on under the hood and it’s not fixed. There’s always a matrix operation in there somewhere and that affects color only, NOT NEUTRALS.

 

I’ve told this story before but it’s always relevant:

 

Years ago my regular video engineer and I met with an engineer at Bexel to get a quick training on this new thing called “HD.” I had a specific question about the Sony F900 user matrix and the engineer made the point that I shouldn’t touch it lightly. He placed a gray card in the middle of the set, zoomed in on it, and put random numbers into the user matrix. Nothing changed. Then he zoomed out. Every color on the set was whacked.

 

The Sony F900, like most broadcast-style cameras, had four separate matrix operations happening in a chain: at the bottom you had the OHB (optical head block) matrix meant to correct for color variances in prism blocks, then the matrix that defines the color space (Rec 709, NTSC, EBU), then the user matrix (to allow the user to adjust overall color as desired), and then a vector matrix (to allow the user to adjust individual hues within a set range). None of these  affect white, gray or black.

 

Modern cine cameras don’t have this exact setup but there’s always at least one matrix operation happening somewhere in the imaging chain.

 

As the color science in digital is extremely malleable and exists primarily in software, it’s very easy to get lost. A gray card will help you balance the red, green and blue gains but that’s a very basic operation (white balance) and is usually only the first step in creating viable color. The spectral response curves of the CFA filters overlap and those signals must be added to and subtracted from each other to create basic color. That’s what a matrix does. It’s a fundamental operation that affects color in every way but it won’t touch white, black or gray.

 

To sum up: if you’re just trying to correct an overall color cast, a white or gray reference is just fine. If something is skewed in the camera matrix (or there’s a LUT imposed and it’s the wrong LUT) you can’t save yourself unless you have known color references to work from.

 

Generally the least you need for terrestrial efforts is white/black/gray, red/green/blue, yellow/cyan/magenta, and it helps to have a flesh tone reference.

 

I’m assuming the image processing for off-world image capture happens here on Earth. If color looks a bit strange there’s no way to know if that’s due to the subject or the image processing. If you have color references on location then you can figure this out because you can solve for the color references. A neutral reference is not enough.

 

 

_______________________________________________________​
Art 
Adams
Cinema Lens Specialist
​
ARRI Inc.
3700 Vanowen Street
Burbank, CA 91505
www.arri.com 

818-841-7070
x4212
 
aadams@...

Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.


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This message is confidential. It may also be privileged or otherwise protected by work product immunity or other legal rules. If you have received it by mistake, please let us know by e-mail reply and delete it from your system; you may not copy this message or disclose its contents to anyone. Please send us by fax any message containing deadlines as incoming e-mails are not screened for response deadlines. The integrity and security of this message cannot be guaranteed on the Internet.
Art Adams
 

I would think it would send raw back. Processing the image before transmission seems like a waste of processing power and energy when you could do it just as easily on Earth, plus you can update the processing software more easily and troubleshoot the image data without tying up the rover.

 

That’s just a guess.

 

-Art

 

_______________________________________________________​
Art 
Adams
Cinema Lens Specialist
​
ARRI Inc.
3700 Vanowen Street
Burbank, CA 91505
www.arri.com 

818-841-7070
x4212
 
aadams@...

Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.


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​

This message is confidential. It may also be privileged or otherwise protected by work product immunity or other legal rules. If you have received it by mistake, please let us know by e-mail reply and delete it from your system; you may not copy this message or disclose its contents to anyone. Please send us by fax any message containing deadlines as incoming e-mails are not screened for response deadlines. The integrity and security of this message cannot be guaranteed on the Internet.


From: cml-raw-log-hdr@... <cml-raw-log-hdr@...> on behalf of Noel Sterrett via cml.news <noel=admitonepictures.com@...>
Date: Sunday, February 28, 2021 at 3:40 PM
To: cml-raw-log-hdr@... <cml-raw-log-hdr@...>
Subject: Re: [cml-raw-log-hdr] Color Charts for Mars

Anyone know if it sends RAW back, or de-Bayer/process first?

 
Noel Sterrett
 

I would guess RAW as well.

Many of the same arguments I would offer in the design of this remote camera, could be used for the design of the cameras we use.

On 3/1/21 1:04 PM, Art Adams wrote:

I would think it would send raw back. Processing the image before transmission seems like a waste of processing power and energy when you could do it just as easily on Earth, plus you can update the processing software more easily and troubleshoot the image data without tying up the rover.

 

That’s just a guess.

 

-Art

 

_______________________________________________________​
Art  
 Adams
Cinema Lens Specialist
​
ARRI Inc.
3700 Vanowen Street
Burbank ,  CA   91505
www.arri.com 
818-841-7070
x4212
 


aadams@...

Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.


​

​

This message is confidential. It may also be privileged or otherwise protected by work product immunity or other legal rules. If you have received it by mistake, please let us know by e-mail reply and delete it from your system; you may not copy this message or disclose its contents to anyone. Please send us by fax any message containing deadlines as incoming e-mails are not screened for response deadlines. The integrity and security of this message cannot be guaranteed on the Internet.

From: cml-raw-log-hdr@... <cml-raw-log-hdr@...> on behalf of Noel Sterrett via cml.news <noel=admitonepictures.com@...>
Date: Sunday, February 28, 2021 at 3:40 PM
To: cml-raw-log-hdr@... <cml-raw-log-hdr@...>
Subject: Re: [cml-raw-log-hdr] Color Charts for Mars

Anyone know if it sends RAW back, or de-Bayer/process first?

 
Noel Sterrett
 

A grey card helps identify the white point of the scene. How the camera reacts to that is camera dependent.

On 3/1/21 1:02 PM, Art Adams wrote:

>>>A grey card seemed to work well for a long time….

 

That’s because film has the color science baked in. If you print the gray card as neutral then everything else falls in line (depending on the processing, of course, and even then I don’t think you could seriously skew the color short of cross processing or doing something very strange).

 

Digital is completely different. There’s a lot of math going on under the hood and it’s not fixed. There’s always a matrix operation in there somewhere and that affects color only, NOT NEUTRALS.

 

I’ve told this story before but it’s always relevant:

 

Years ago my regular video engineer and I met with an engineer at Bexel to get a quick training on this new thing called “HD.” I had a specific question about the Sony F900 user matrix and the engineer made the point that I shouldn’t touch it lightly. He placed a gray card in the middle of the set, zoomed in on it, and put random numbers into the user matrix. Nothing changed. Then he zoomed out. Every color on the set was whacked.

 

The Sony F900, like most broadcast-style cameras, had four separate matrix operations happening in a chain: at the bottom you had the OHB (optical head block) matrix meant to correct for color variances in prism blocks, then the matrix that defines the color space (Rec 709, NTSC, EBU), then the user matrix (to allow the user to adjust overall color as desired), and then a vector matrix (to allow the user to adjust individual hues within a set range). None of these  affect white, gray or black.

 

Modern cine cameras don’t have this exact setup but there’s always at least one matrix operation happening somewhere in the imaging chain.

 

As the color science in digital is extremely malleable and exists primarily in software, it’s very easy to get lost. A gray card will help you balance the red, green and blue gains but that’s a very basic operation (white balance) and is usually only the first step in creating viable color. The spectral response curves of the CFA filters overlap and those signals must be added to and subtracted from each other to create basic color. That’s what a matrix does. It’s a fundamental operation that affects color in every way but it won’t touch white, black or gray.

 

To sum up: if you’re just trying to correct an overall color cast, a white or gray reference is just fine. If something is skewed in the camera matrix (or there’s a LUT imposed and it’s the wrong LUT) you can’t save yourself unless you have known color references to work from.

 

Generally the least you need for terrestrial efforts is white/black/gray, red/green/blue, yellow/cyan/magenta, and it helps to have a flesh tone reference.

 

I’m assuming the image processing for off-world image capture happens here on Earth. If color looks a bit strange there’s no way to know if that’s due to the subject or the image processing. If you have color references on location then you can figure this out because you can solve for the color references. A neutral reference is not enough.

 

 

_______________________________________________________​
Art  
 Adams
Cinema Lens Specialist
​
ARRI Inc.
3700 Vanowen Street
Burbank ,  CA   91505
www.arri.com 
818-841-7070
x4212
 


aadams@...

Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.


​

​

This message is confidential. It may also be privileged or otherwise protected by work product immunity or other legal rules. If you have received it by mistake, please let us know by e-mail reply and delete it from your system; you may not copy this message or disclose its contents to anyone. Please send us by fax any message containing deadlines as incoming e-mails are not screened for response deadlines. The integrity and security of this message cannot be guaranteed on the Internet.

Art Adams
 

>>>A grey card helps identify the white point of the scene. How the camera reacts to that is camera dependent.

That’s a better way of saying that. And, as best I can tell, that’s just a gain adjustment.

_______________________________________________________​
Art 
Adams
Cinema Lens Specialist
​
ARRI Inc.
3700 Vanowen Street
Burbank, CA 91505
www.arri.com 

818-841-7070
x4212
 
aadams@...

Get all the latest information from www.arri.com, Facebook, Twitter, Instagram and YouTube.


​

​

This message is confidential. It may also be privileged or otherwise protected by work product immunity or other legal rules. If you have received it by mistake, please let us know by e-mail reply and delete it from your system; you may not copy this message or disclose its contents to anyone. Please send us by fax any message containing deadlines as incoming e-mails are not screened for response deadlines. The integrity and security of this message cannot be guaranteed on the Internet.
Martyn James Bull
 

Summary review of all cameras on Perserverance. 

Raw data sent sent back to Earth for archiving at JPL. 

https://link.springer.com/article/10.1007/s11214-020-00765-9#citeas

The Mars 2020 Engineering Cameras and Microphone on the Perseverance Rover: A Next-Generation Imaging System for Mars Exploration

    • J. N. Maki, 
    • D. Gruel, 
    • […]
    • S. Algermissen 

Space Science Reviews volume 216, Article number: 137 (2020)

best regards 

martyn 

Martyn J Bull
filmaker 
oxfordshire, uk
BarrySchwartz
 

Here's a little more on the cameras, from a photo newsletter, PetaPixel: "A Closer Look at the Mars Perseverance Rover’s Incredible Cameras"

https://petapixel.com/2021/03/01/a-closer-look-at-the-mars-perseverance-rovers-incredible-cameras/

Barry Schwartz
Barry Schwartz Photography
Napa, CA
+1 310 721 9882
barry@...

Photo  barryschwartzphoto.com
Blog  barryschwartznotbarryschwartz.com
Noel Sterrett
 

Interesting zoom lens mechanism, but how can you get great looking bokeh on closeups of Martians at F/7?
Noel Sterrett | Admit One Pictures | Atlanta

On 3/2/21 1:38 PM, BarrySchwartz wrote:
Here's a little more on the cameras, from a photo newsletter, PetaPixel: "A Closer Look at the Mars Perseverance Rover’s Incredible Cameras"

https://petapixel.com/2021/03/01/a-closer-look-at-the-mars-perseverance-rovers-incredible-cameras/

Barry Schwartz
Barry Schwartz Photography
Napa, CA
+1 310 721 9882
barry@...

Photo  barryschwartzphoto.com
Blog  barryschwartznotbarryschwartz.com

Gary Adcock
 

Art, 
I would venture to say that Perseverance is sending something akin to raw binary data back, that would allow greater areas of exploration of UV, IR and other parts of the visible and non-visible spectrum we should be extrapolating data from.  It would be true waste of resources if we went all the way to Mars and only looked for what we already know of, searching in and beyond the extended spectrum of “waves" that vibrate throughout what we know of in our universe in the form of sound, light, motion, and radio could become evolutionary. 



On Mon, Mar 1, 2021 at 12:04 PM, Art Adams wrote:
I would think it would send raw back. Processing the image before transmission seems like a waste of processing power and energy



Gary Adcock
techy as long as my zoom connection holds out
Chicago, IL   USA
Noel Sterrett
 

Really great stuff. Not sure why it's so fascinating. Perhaps pandemic relief.

Cheers.
Noel Sterrett | Admit One Pictures | Atlanta

On 3/2/21 1:36 AM, Martyn James Bull via cml.news wrote:
Summary review of all cameras on Perserverance. 

Raw data sent sent back to Earth for archiving at JPL. 

https://link.springer.com/article/10.1007/s11214-020-00765-9#citeas

The Mars 2020 Engineering Cameras and Microphone on the Perseverance Rover: A Next-Generation Imaging System for Mars Exploration

    • J. N. Maki, 
    • D. Gruel, 
    • […]
    • S. Algermissen 

Space Science Reviews volume 216, Article number: 137 (2020)

best regards 

martyn 

Martyn J Bull
filmaker 
oxfordshire, uk
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