Magenta Tint

The place for questions about shooting with Blackmagic Cameras.
  • Author
  • Message
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Magenta Tint

PostMon Mar 05, 2018 11:49 am

Hey guys,

Check out this clip and go to 18 seconds in and look at the rim of the brown horses's nose. This is some footage I got with my URSA Mini Pro. There is a magenta tinge there which is a lot more noticeable in the uncompressed file as opposed to YouTube's compressed version. I have specifically noticed this when using the built in ND filters and when I aim the camera at a bright sky, but now with this clip it seems to show that the magenta can pop up at any time. What gives? And what can I do about it other than spam green through the image in post?

I'm guessing this is why a "10 tint" setting is the default option that is set on the URSA Mini Pro and was used during the commercial Blackmagic produced for the camera.

Many thanks,
James

Offline

roger.magnusson

  • Posts: 388
  • Joined: Wed Sep 23, 2015 4:58 pm
  • Location: Sweden

Re: Magenta Tint

PostMon Mar 05, 2018 4:15 pm

I haven't checked with scopes, but it looks like one or more RGB channels clipped since the highlights are overexposed.

Regarding +10 tint, more info here. But the values may need to be changed to calibrate your particular camera.
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Re: Magenta Tint

PostMon Mar 05, 2018 5:17 pm

roger.magnusson wrote:I haven't checked with scopes, but it looks like one or more RGB channels clipped since the highlights are overexposed.

Regarding +10 tint, more info here. But the values may need to be changed to calibrate your particular camera.


Hi Roger thanks for your reply. I do not think this has anything to do with overexposure as Im reviewing my footage that I took while at a park which was covered in a blanket of snow and none of the shots are overexposed yet there is the appearance of a magenta tint in the sky and all around the silhouttes of the people in the park.
Offline

Kyle Gordon

  • Posts: 403
  • Joined: Thu Dec 26, 2013 4:06 am

Re: Magenta Tint

PostMon Mar 05, 2018 5:25 pm

That magenta edging is called chromatic aberration, and it's an artifact of the lens, not the camera.
Kyle Gordon
Professional Singer/Composer/Producer and Director/Editor/Colorist
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Re: Magenta Tint

PostMon Mar 05, 2018 5:43 pm

Kyle Gordon wrote:That magenta edging is called chromatic aberration, and it's an artifact of the lens, not the camera.


I see. Thank you very much for the clarification. Do you have any advice on how to counter it on set or in post or are all lens artifacts pretty much final?
Offline

Keith Babineaux

  • Posts: 95
  • Joined: Wed Mar 30, 2016 8:56 pm
  • Location: Miami, FL

Re: Magenta Tint

PostMon Mar 05, 2018 6:11 pm

James McDonagh wrote:
Kyle Gordon wrote:That magenta edging is called chromatic aberration, and it's an artifact of the lens, not the camera.


I see. Thank you very much for the clarification. Do you have any advice on how to counter it on set or in post or are all lens artifacts pretty much final?


CA on lens is final. You can't fix it in post. You'll have to use different lens. Which lens is that? I'll make sure to avoid it in the future.
Keith Babineaux | Film Student | Full Sail University
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Re: Magenta Tint

PostMon Mar 05, 2018 6:13 pm

Keith Babineaux wrote:
James McDonagh wrote:
Kyle Gordon wrote:That magenta edging is called chromatic aberration, and it's an artifact of the lens, not the camera.


I see. Thank you very much for the clarification. Do you have any advice on how to counter it on set or in post or are all lens artifacts pretty much final?


CA on lens is final. You can't fix it in post. You'll have to use different lens. Which lens is that? I'll make sure to avoid it in the future.


rokinon cine lenses
Offline

roger.magnusson

  • Posts: 388
  • Joined: Wed Sep 23, 2015 4:58 pm
  • Location: Sweden

Re: Magenta Tint

PostMon Mar 05, 2018 6:37 pm

Oh, I'm talking about another artefact, sorry. I couldn't watch anything else after seeing it. :)

Horse R239, G255, B255.jpg
Horse R239, G255, B255.jpg (99.4 KiB) Viewed 739 times

The white horse is cyan because the green and blue channels are clipped. RGB values 239,255,255
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Re: Magenta Tint

PostMon Mar 05, 2018 7:27 pm

roger.magnusson wrote:Oh, I'm talking about another artefact, sorry. I couldn't watch anything else after seeing it. :)

Horse R239, G255, B255.jpg

The white horse is cyan because the green and blue channels are clipped. RGB values 239,255,255


Oh wow, thank you! That makes sense... so basically it's because of too much light flooding the sensor? That makes a lot of sense, thank you.
Offline

Earl R. Thurston

  • Posts: 150
  • Joined: Sun Sep 04, 2016 4:52 pm
  • Location: Burnaby, BC

Re: Magenta Tint

PostMon Mar 05, 2018 7:35 pm

James McDonagh wrote:... so basically it's because of too much light flooding the sensor?

Or possibly the colour correction, grading or LUT mapped this area into overexposure. If this was shot RAW it's possible there is more sensor data available for highlight recovery than was used in this output.
Offline

Uli Plank

  • Posts: 2575
  • Joined: Fri Feb 08, 2013 2:48 am

Re: Magenta Tint

PostMon Mar 05, 2018 9:56 pm

Since we are using Bayer patterns in our sensors, it's quite possible to saturate one group of photo cells and not the others if any color has much more energy than the rest. Remember the infamous pink highlights?
Offline

Ric Murray

  • Posts: 28
  • Joined: Tue Nov 07, 2017 8:45 pm
  • Location: North Kingstown, RI USA

Re: Magenta Tint

PostThu Mar 08, 2018 9:28 pm

James,

Not trying to haunt you here, but this goes back to the other thread "Cinematography Case Study". Once the sensor gets flooded or clipping occurs all kinds of things go off the rails. Simple solution is to use the histogram and expose for the highlights, light (or fill) for the shadows, and adjust the Gamma in software, either Premiere or Resolve or anything else you like. The LCD is there for composition & framing, It's not a calibrated monitor.
Creativity is the ability to accept ambiguity.
Offline

James McDonagh

  • Posts: 105
  • Joined: Fri Dec 01, 2017 5:38 pm

Re: Magenta Tint

PostThu Mar 08, 2018 10:46 pm

Ric Murray wrote:James,

Not trying to haunt you here, but this goes back to the other thread "Cinematography Case Study". Once the sensor gets flooded or clipping occurs all kinds of things go off the rails. Simple solution is to use the histogram and expose for the highlights, light (or fill) for the shadows, and adjust the Gamma in software, either Premiere or Resolve or anything else you like. The LCD is there for composition & framing, It's not a calibrated monitor.


Hi Ric,

Don't worry about haunting me I sincerely appreciate all the feedback and help! Thank you for your input. As you could see on this thread some people thought that the magenta was an artifact from the lens and not a product of overexposure. I'm glad to hear everyone's opinons and thoughts thank you :)
Offline

Kyle Gordon

  • Posts: 403
  • Joined: Thu Dec 26, 2013 4:06 am

Re: Magenta Tint

PostFri Mar 09, 2018 5:22 pm

It depends what you're talking about.

The purple fringe on the brown horses nose where it meets with the white behind it is chromatic aberration from the lens. The cyan tint of the white horse behind is color channels clipping.
Kyle Gordon
Professional Singer/Composer/Producer and Director/Editor/Colorist

Return to Cinematography

Who is online

Users browsing this forum: No registered users and 8 guests