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Question

Adjusting curves numerically

Forum|Forum|3 years ago
December 7, 2022
2 replies
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I am a still photographer first and videographer second. I use the curves feature every day in Photoshop to tone my images. Today, I am color grading video footage in Premiere Pro CC 2023.

As I use curves in the color workspace of Premiere Pro, I have always wished I could adjust the curves values numerically like I can in Photoshop - adjusting incrementally by taps of the arrow keys rather than having to drag points with my mouse. Sometimes the adjustments I need to make are extremely fine and it is very difficult to get them just right by dragging the mouse.

Anyone else deal with this problem?

Editing

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Keith23242116exw5

Known Participant

Hi - I'm new here & can't find how to post a "new" question, so forgive me.

On the topic of curves, LRC v 12.1 Jan 2023, I am finding that when moving or creating the points on the curve, they "snap back" to a different position than that selected, (not back to the originial that is, just different from that which I selected.) Is it just me? Am I doing something wrong or is it a general issue?

Thanks in advance PS If anyone can advise on how to start a new question that would be great!

R Neil Haugen

Legend

Having come into video post out of a long stills career, at first I also tried to equate video and stills color. They are by nature two very different beasts, and though some of your skills and technique will still apply, many concepts and practics must be adapted to this medium's needs and possibilities.

I don't know a video post app that allows for digital entry of numbers for a Curves panel. Might exist, but if so, I've neither heard of nor seen it. And I work for/with/teach pro colorists.

When working in the Curves panel in Lumetri, it's wise to make the Lumetri panel as wide as possible to get a larger curves box to work with. Very helpful when doing color to have a 'clean feed' monitor, using the Transmit Out option, so you don't need to see the image on the UI screen.

The two UI panels you need to see best are the Scopes panel and that Curves tab. Those should be big, with either the RGB Parade or Waveform scope showing. Or both. You can see your 'end' point locations in the scopes then. Then the Program monitor on the UI screen is irrelevant and can be tiny or simply removed as wasted space.

Remember, there is a major difference in video color compared to stills color ... a still image is static. Absolute. The original data doesn't change ... ever. A video image is not static, it is constantly changing. So for example, the blackest point from one frame from a contiguous section of a clip may actually vary slightly from a few frames later. Or before.

And the computations for a single image in a still can be lengthy and complex, and still be processed nearly immediately. For video, the same work requires that computation be done 24 to 60 times per second. The behind the scenes system must work differently or choke the computer.

And absolute numbers aren't all that useful except for QC work.

I have also put in a feature request for getting splines in the Curves tool in Lumetri. Those are marvelous for doing subtle shaping, far better than even numerical entry for the values within the scale.

Neil

Everyone's mileage always varies ...

J

jmcwhorter11Author

Participant

Thank you! Doesn't necessarily solve the problem, but I really appreciate you taking the time to respond and giving some helpful insight. It's good to know that someone else has at least thought about it.

R Neil Haugen

Legend

Most welcome.

I would note that another easy thing to fall into is thinking that the Basic tab tools are like unto the Lightroom tools ... um ... no, not hardly. The UI mimics the LR tonal/sat tools. But the work done is different in both subtle and at times dramatic ways, again because ... video not stills.

Using Exposure for instance to move the general brightness up or down, centering the 'middle values' on the all-important 50IRE middle of the Scopes scale.

Why? Contrast will expand or contract image contrast equally towards highs and lows but always from the middle 50IRE value on the scales. So if you center what you want to be 'middle' prior to touching Contrast, it works slick and "as expected".

Whites works as expected ... similar to grabbing the whites end point on the curves panel and moving it up or down.

Blacks ... nope. Blacks is like a swinging door set to 'hinge' about values 8-10 in 8-bit numbers on the left side. Not exactly what you expect, and doesn't affect anything above about 15.

So use Shadows to adjust your lower values, then Black just to 'touch' the actual black point.

Color Wheels confuse people too. Shadows starts at Black point as you'd expect, but doesn't affect only shadows, it simply affects them more than mids, and to a lesser extent, highs.

Same with Highlight wheel. And Mids. These are in colorist terms Lift, Gamma, and Gain tools left to right.

So when lifting Shadows brightness, you also typically need to pull Mids down a bit to keep that Shadows adjustment in the shadows. As one example.

Or if pushing shadows to "cool" values, for color, you need to push mids exactly the opposite direction to keep from cooling your mids. Watching scopes tells you better than the image what you are doing.

Neil

Everyone's mileage always varies ...

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