DRAGON + Cooke Anamorphic Circular purple falre pattern

[Tim Sessler]

Hey everybody -

I am currently shooting a piece in Alabama with my Dragon (Low-light OLPF) and the wonderful Cooke Anamorphics.
So far everything has been beautiful but yesterday morning I found a very strange issue that I have not been able to solve so far:

Shooting straight into the sun at f/11 a pattern of circular, of even spaced, purple spots show up all over the frame.

No ND or mattebox was used.

Here is a screenshot:

At first I assumed it had to be an issue of dirt on one of the elements or possibly even the sensor/OLPF - but everything is clean and the pattern is too accurate to be dirt/dust related.
My next idea was a faulty black shade - but testing multiple backshades and shooting at different frame rates did not change anything.

Curious to hear if anybody has experienced this or if anybody has any advice on how to fix this.

Thanks,
Tim

 

[Jake Wilganowski]

It's totally normal, you CANT shoot with this high a stop at the sun, this is what happens with the low light olpf

 

[Jake Wilganowski]

If you can't use ND, shoot a higher shutter so you can open up a couple stops

 

[Jaume Jardí]

Hi Tim,
These artifacts are due to low light OLPF and when shooting f / 11.
With standard OLPF or skin tone OLPF these artifacts disappear or are minimal

 

[Jake Wilganowski]

It's interesting too because what this shows is how magenta- contaminated the lowlight olpf is when shooting at bright sources, when using a lower f-stop it is just out of focus so you can't see it's pattern, but the color cast is there

 

[Tim Sessler]

It's totally normal, you CANT shoot with this high a stop at the sun, this is what happens with the low light olpf

WOW - if thats right, thats crazy! I've been shooting with primarily the LLO OLPF for the past 1.5 years and never seen this before. I have to dig through some footage but I am certain that I've shot super high f stop footage straight into the sun before and have not experienced this issue. Although I might still had used some ND and spherical glass instead of the anamorphic Cookes. Would the lens or type of coating of the glass contribute to this phenomena or is it purely an LLO OLPF issue?

 

[Jake Wilganowski]

Nothing to do with lens optics or anamorphic. It's purely the fact that when stopped down these come into focus, and the sun has to be nailing the lens just right

 

[Jake Wilganowski]

Different olpf's don't have this, just low light

 

[Tim Sessler]

Different olpf's don't have this, just low light

Wow - thats good to know. THANKS!!