Grade correct advice

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Alexandre Garacotche

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Grade correct advice

PostFri Jun 22, 2018 8:49 pm

Hello,

I have this clip that while being shot its exposition has been changed.
Precisely, the aperture has been raised down resulting in a clip overexposed at start to a correctly exposed one.
I need your advice on how to best reduce the exposition change.
So far I have sliced it into pieces corresponding to each exposition state. I have grabbed a still of the targeted slice (the well exposed) and tried to work my way back slice by slice and match the still using the offset wheel and the controlling the highlight in the log tab, but this is really tough.
Maybe some with more experience could advice on a better approach.

Thanks.
Alexandre
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Peter Benson

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Re: Grade correct advice

PostSat Jun 23, 2018 12:31 am

Oh, no, not with OFFSET, Alexandre!

Yuck! New to DaVinci Resolve color-grading as I am, even I myself would strongly advise against another newbie tampering with OFFSET, as I personally observed OFFSET adjustment potentially makes for a much greater mess of things, compared to alternate Color Wheel (or alternate Color Slider) paramaters you might have selected to tweak instead.

If you know not what you're doing, for goodness' sake, leave OFFSET alone. Reset it, let it alone and start over, using other available controls guided by easily accessible, pertinent Resolve 14 YouTube tutorials you specifically search for (with keywords indicating your issue/problem, source file condition or remedy you're aiming for) is my earnest advice for you.

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Marc Wielage

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Re: Grade correct advice

PostSun Jun 24, 2018 3:31 am

I think there's a lot of "it depends" here. How overexposed does the shot get? If it's gigantically overexposed, it'll never be normal. You can make it better to some degree, but it's very difficult to make it absolutely perfect, because it's a non-linear change.

One approach would be to set the offset in the middle of the exposure, then use Lift/Gamma/Gain (and possibly curves or contrast/pivot) to manually help the exposure. Instead of splitting the clip into multiple pieces, I'd just keyframe it manually in the Color Keyframe window. All of this is covered in the user's guide.
marc wielage, csi • VP/color & workflow • chroma | hollywood
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JPOwens

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Re: Grade correct advice

PostMon Jun 25, 2018 5:50 pm

Marc Wielage wrote:it'll never be normal.


Most cinematographers think that because the exposure is a linear change (twisting the T-stop) that "Fixing an over-exposure" in post will be the same approach, *just crank down the gain...*

Of the several hundred times down this rabbit-hole, not once has this been true, and all of them have had different characteristics. Everything about the image profile is different -- the grey scale rides up and down the gamma curve non-linearly, chromatic flare goes sideways... and depending on the nature of what caused the departure -- error on the lens, lighting bounce, whatever, and the ballistics of the change (smooth climb, digital jump, motor drive overshoot and hunt with an auto-exposure), a colorist is almost always condemned to keyframing and a soul-destroying flip-and-compare, then play-through to smooth out the chaos.

At a certain point, the question of whether the performance is so good that the take is worth saving will come up. Better be a Ming vase to justify all that crazy glue.

jPo, CSI
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Alexandre Garacotche

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Re: Grade correct advice

PostMon Jul 02, 2018 8:26 am

Thank you for each of your advice.
I'll do what I can.
Alexandre
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Dermot Shane

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Re: Grade correct advice

PostFri Jul 06, 2018 4:33 am

i agree the law of dimishing returns sets n pretty quickly on a bad day

but i would turn to offset first, but in ACES / linear light so it reacts like a t-stop on a lens, i can beat lot of stop pulls with that alone, i use it in the first node, before any other color effects

also worth playing with is the "color stabliser" in Resolve's native OFX, sometimes it does an awesome job, sometimes it's so bad it's truly comical / funny

BCC's de-flicker can also beat some stop pulls, again hit and miss, but if it hiits, smiles all around...
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Howard Roll

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Re: Grade correct advice

PostSat Jul 07, 2018 5:40 am

How about using a color space transform to change it to linear then keyframe the gain.

Good Luck
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Alexandre Garacotche

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Re: Grade correct advice

PostMon Jul 16, 2018 7:57 pm

Dermot Shane wrote:but i would turn to offset first, but in ACES / linear light so it reacts like a t-stop on a lens, i can beat lot of stop pulls with that alone, i use it in the first node, before any other color effects


Can you be more specific on the ACES set up you'd use please ?

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