Fixed Pattern Noise From Alexa Mini

[jjLDN]

Hi Everyone,

Just wanted to ask about fixed pattern noise on a recent shoot with Alexa Mini in Anamorphic mode. After completing our shoot which consisted of both interior and exterior setups, my AC noticed that despite setting SENSOR > Image Denoising to 'normal', it had somehow reset itself to 'off'.

At first this didn't concern me greatly, as we were shooting at ISO 800 for majority of the day, and I've always found Arri's noise to be quite organic and pleasing. I'd also not seen anything on any of our monitors including a 17inch OLED that had worried me. It wasn't until I looked at the rushes much closer, and noticed the most bizarre fixed pattern noise I've ever seen.

What appears to be happening is literally every second line of the sensor blocking to what seems to be solid green. It is thoroughly throughout the entire image, but seems to especially affect a specific band on the lower end of the highlights. When attempting to grade the image, it feels incredibly 'thin' and blows out very quickly.

I'm finding this incredibly bizarre, as according to the manual, image denoising from the sensor is by default set to 'off' - but the results here are borderline unusable. Interestingly, at the very end of the day we set the sensor denoising to 'normal' - and all footage shot with this setting was typical beautiful Alexa sensor footage.

So I guess my two questions are, why on earth is there even an option to turn off sensor denoising if the results are so damaging to the footage, and has this happened to anyone else? Any advice on removing Alexa FPN? An initial test is not looking promising.

Any help much appreciated,

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[Jonas Poetschke]

Hi jjLDN,

my colleague contacted you offline to sort this out.

Best regards,
Jonas