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Arri Alexa and "pixel gridding"


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3 hours ago, Tyler Purcell said:

The shot of the window, no way that was "clipping". Did you see the histogram or waveform when you were shooting?

I use light meter readings to determine the exposure and check the highlights with the spot meter. Occasionally I use the built inn false colors to check the highlights. The window in the top image is not clipping as far as I remember (it only looks like it due to the grading). But there is a tweenie as a backlight in that same image (that is cropped out) which is clipping. 

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10 hours ago, Kristian Sundsvalen said:

I use light meter readings to determine the exposure and check the highlights with the spot meter. Occasionally I use the built inn false colors to check the highlights.

Yea false color is good to have for sure. I use Zebra's because they can stay on all the time and they don't disturb the image very much. That mixed with the histogram and waveform in the corner, really helps prevent these things. I only use the meter to figure out contrast ratio because highlight dynamic range on digital imagers can be a bit tricky to determine without the digital tools. 

10 hours ago, Kristian Sundsvalen said:

But there is a tweenie as a backlight in that same image (that is cropped out) which is clipping. 

Ahh interesting, but generally you won't get this pattern unless the light is pointed at the camera. 

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2 hours ago, Gregory Irwin said:

Can you copy and paste the Arri file from this clip?

G

I only have one of the clips from the images. But I have made a new quick test. Her is links to download the ArriRaw- files:

https://wetransfer.com/downloads/d4c2c0b8f905f641148f5c559ca0a8aa20210607203655/f4dec92746429f170f7a8e42f91b88c020210607203655/78b417

 

https://wetransfer.com/downloads/1c22e88b951391016383c484cd1102ad20210607204640/e9a6d99d3e37080403e50bc1f39e8e1a20210607204640/b3b9ea

On clip A004C045 you should see the patterns on the white curtain. The sky outside the window is clipping, so I believe that is what is trigger the patterns.

 

This are JPEG from the images I posted previously in this thread:

https://we.tl/t-UTyRlem9TQ

 

Edited by Kristian Sundsvalen
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Sorry for taking so long with this, I’m on set everyday on a very demanding movie that is requiring my full attention. But for now, the evidence is suggesting a compression issue. We are still looking at the data you provided but at the moment, that’s the current thinking. I sadly don’t have any further information. Hope this helps. 
 

G

Edited by Gregory Irwin
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On 6/9/2021 at 9:42 PM, Gregory Irwin said:

Sorry for taking so long with this, I’m on set everyday on a very demanding movie that is requiring my full attention. But for now, the evidence is suggesting a compression issue. We are still looking at the data you provided but at the moment, that’s the current thinking. I sadly don’t have any further information. Hope this helps. 
 

G

I appreciate the time and effort you have put into this. All the best luck with your ongoing movie.

Edited by Kristian Sundsvalen
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