F55: Fattening up your F55 digital negative?

Grug

Grug

Veteran
Hey guys,

I've got my first shoot with the F55 on the weekend, we'll be recording to XAVC internally (probably in 4K), and I'm wondering what settings I'll want to input to get the fattest possible negative out of the 10-bit XAVC? Do I just set it to SLOG2 and S-Gamut and leave her be? Or does it help to get a little fancier with the setup?

And what ISO do you rate the camera at (at your preferred settings)? I remember the original stat being 1250(?) ISO, but is that for SLOG2, or Rec709?

Cheers
 
Ok, sprinkled with "in my opinion, and I've done a LOT of testing"

If you have the proper post deals to deal with it, yes, S-Log2 & S-Gamut in XAVC will net you spot-on Alexa images. Turning on S-Gamut in System will lock out all detail, matrix, etc.

Anything else, again, starts to veer into video-ish territory. Hypergammas, etc.

This is something somebody else shot between setups while testing my cam...this is S-Log/S-Gamut processed via ACES* in Resolve.

https://vimeo.com/direktor/review/65794222/f4089169ce

As far as "fat" In S-Log2, rating around 1250 is what it's supposed to be, but 800ish will do you right if you make sure you're not clipping any highlights you need by setting 106 zebras (not 107 or 108). By eye, since there are no LUTs while shooting just S-Log2/XAVC, when correctly exposed it will look underexposed by about a stop or stop and a half. You want the "meat" of your image in the 30-60 IRE range.

If you overexpose in Slog2 by a lot (like skin tones up in the 75-90 area), it becomes tough in post to get it back to linear-ish and have it look good, but it can be done.



*[a colorist has tuned me into to some tech problems with ACES in Resolve, and he's right about all of them, but in most cases I think it's still the best choice to get a good image. Just keep a sharp eye out for clipping artifacts]
 
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I don't want to derail Mark's thread. I'll try to finish with ACES what I started somewhere else.

To answer Mark's question more completely, feel free to rate the camera at less than 1250 to "fatten", but you lose highlight latitude if you do. Just depends if you need 7 stops above grey or not. Many times you don't.

The truth I'm learning is that the if you turn off Noise Reduction in the "Camera" menu, the sensor is noisier than you might guess. Exposing S-Log at 1250 then will make for visible (but not obnoxious) noise in shadows as de-logging the image in post brings that noise floor up 15 or so IRE.

If you leave NR on Low or Mid and expose at 1250, the noise visible after de-logging is much more in line with what you'd expect (barely visible, if at all).
 
Thanks Nate, that's a huge help! We're shooting outside so I think we'll go with 1250 to keep as much highlight headroom as possible.

Cheers,

Mark
 
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