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F55 saturation and skintones


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#1 John Miguel King

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Posted 15 February 2014 - 03:17 AM

Hi all,

 

I´m grading a promo I shot on the F55 and I keep seeing wild shifts in the saturation of the red channel that's making skintones jump all over the place.

First, I wonder if I'm the only person finding this issue.

Second, I keep getting opposite views as to the nature of the camera's internal ND. Sony won't confirm they are IRND, which sort of says they aren't. This would be a very plausible explanation.

Another explanation that would compound the issue, and I'm reading this article by Art Adams, would be the way the camera renders colour.

Anybody else out there has come accross this issue?

Sort of makes the camera unusable, no?


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#2 Rafael Rivera

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Posted 19 February 2014 - 03:19 AM

Hi all,

 

I´m grading a promo I shot on the F55 and I keep seeing wild shifts in the saturation of the red channel that's making skintones jump all over the place.

First, I wonder if I'm the only person finding this issue.

Second, I keep getting opposite views as to the nature of the camera's internal ND. Sony won't confirm they are IRND, which sort of says they aren't. This would be a very plausible explanation.

Another explanation that would compound the issue, and I'm reading this article by Art Adams, would be the way the camera renders colour.

Anybody else out there has come accross this issue?

Sort of makes the camera unusable, no?

 

I recently visited the DMPC on the Sony lot and the rep did state clearly that the built in filters are IRND's. He also said that any external filters used should also be IRND's. So just guessing, did production used any external ND filters? And out of curiosity, did production shoot raw or XAVC?


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#3 John Miguel King

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Posted 02 March 2014 - 05:00 AM

I now believe it was down to the actor's skin reacting to the weather. :D

Although I haven't tested the internal NDs on the camera properly as of yet... IRND tend to shift the colour in one direction or another, even the Schneiders. So I'm like not too confident in using them internal NDs again until I know exactly which way the vectorscope goes.

So, I used internals and XAVC. Never again going the XAVC way if I can help it. Reason being not so much the quality of the footage, but how very annoying the whole Mlut business becomes once you go that way and start throwing some S&Q at it. Plus the ACES workflow being the way forward with RAW.

When in RAW, the camera is so much more logical, so much more Alexa like. You can change framerate... and that's it. No sudden disappearance of Mluts or whatever.


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#4 John Miguel King

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Posted 30 June 2014 - 03:39 AM

In case you're interested, the F55 is all about colour science. I've been polishing my workflow on this and at the moment I find ACES to be superb when it comes to the grade. All my issues were due to my inept way to work the footage. My procedure, when not able to grade live, is this:

 

1. Load the 40% mlut, therefore exposing middle gray at 40% instead of 33%. I find the camera does plenty of highlight protection, therefore I'm more concerned about not starving the sensor.

 

2. Create proxies with the Alexa-like LUT provided by Sony, the "From_SLog2-SGamut_To_LC-709TypeA". It won't always give a perfect result due to exposing middle gray at 40%, but this is very easy indeed to fix. One issue here, though, is that certain colours, green in particular, get ludicrously saturated. It's not really an issue as we're talking a LUT for proxies here.

 

3. Grade in ACES colourspace.

 

If using Pomfort's Livegrade is a possibility  steps 1 and 2 do change. Livegrade now works on ACES colourspace, so my "solution" is loading a contrasty MLUT just to save my eyes from unnecessary strain when operating, then create the cdl metadata on Livegrade and both bake it and attach it to the proxies.

 

All this results on a much happier grade.


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