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Diffusion filters to mimic Arri Alexa look?


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#1 Alexander Sutton Hough

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Posted 28 February 2018 - 10:45 PM

What diffusion filter would be best to mimic the subtle diffusion look of an Arri Alexa on the Reds, Sony and Panasonic. Currently looking for some to us on a GH5s and Sony FS7. 


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#2 David Mullen ASC

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Posted 28 February 2018 - 10:48 PM

I don’t think the Alexa has a diffused look but if you want to lower contrast to match better, try the lightest Tiffen UltraCon.
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#3 Alexander Sutton Hough

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Posted 01 March 2018 - 12:07 PM

I don’t think the Alexa has a diffused look but if you want to lower contrast to match better, try the lightest Tiffen UltraCon.

But what about the slight softening of super fine detail compared to other digital cameras that makes it more pleasing on skin and film like? 


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#4 David Mullen ASC

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Posted 01 March 2018 - 01:14 PM

What slight softening are you talking about? Are you just referring to the limitations in resolution compared to +4K cameras or the lower contrast in the highlights that roll off to white more smoothly?


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#5 Alexander Sutton Hough

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Posted 01 March 2018 - 05:37 PM

What slight softening are you talking about? Are you just referring to the limitations in resolution compared to +4K cameras or the lower contrast in the highlights that roll off to white more smoothly?

The effect its Optical Low Pass Filter causes? Doesn't the Alexa's OLPF contribute to its filmic look by slightly softening fine detail and lowering the contrast? 


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#6 David Mullen ASC

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Posted 01 March 2018 - 05:51 PM

That's what Red claims but ARRI denies it.  All OLPF's soften fine detail, that's what they are designed to do to minimize aliasing, but Red cameras don't use a milder OLPF than ARRI's do (if anything, maybe the opposite).

 

Some people's tests on the Alexa do show a slight blooming around light sources like candle flames though I don't think the softening is as much as the lightest diffusion filter made... but you can use almost anything in the lightest strength if you want to get some blooming and softening -- 1/8 Black Frost for example.

 

The real advantage to the Alexa is the dual-gain sensor which allows extended overexposure information so highlights roll off more gradually, plus their color science keeps color clipping down to a less obvious level so you don't get some odd color tinge in overexposed skin.

 

If your GH4 or FS7 is producing images that are too sharp, I'd look at how they are being converted from log or raw because I suspect if you look at the original, it's not too sharp, the sharpening is being applied somewhere in the chain to a Rec.709 display image.


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