Brightness & Contrast VS Levels?

VMP wrote on 5/3/2014, 11:34 AM
Often I have heard members here advicing to use the levels/curves instead of the 'Brightness& Contrast' Fx, why is this?

Is the B & C Fx more destructive than the levels/curves FX? If so why? And why is it then included?

I find the B&C to be much easier to tweak than the level curves.
Though I do use the curves for advanced correction.

I am curious.



Chienworks wrote on 5/3/2014, 12:16 PM
Levels and Curves more surely prevent the highs from going past white or the lows below black. They tend to maintain the lightest and darkest parts of the image without losing it. Brightness & contrast both can easily shove part of the brightness range outside of the 0-255 limits and then those portions of the image are lost. So, in a way, yes they are more destructive.

Of course, it's plenty easy to destroy parts of the brightness range with levels too, if you're too heavy handed. I usually stick with curves, which has the most control of all of them and seems to give the smoothest result.

Play with curves for a little while and you'll soon find it's just as fast and easy as brightness and contrast, once you see and understand what it's doing.
musicvid10 wrote on 5/3/2014, 1:26 PM
The ability to roll off the toe and shoulder using Curves is a nice touch.
For quick level conforming and gamma adjustment, Levels works just fine.
I don't use Brightness and Contrast very often for video.
NormanPCN wrote on 5/3/2014, 1:38 PM
Play with curves for a little while

I wish the Vegas curves UI was like Adobe Photoshop curves. The Bezier control point mode of Vegas is slower to work with. For me at least.
paul_w wrote on 5/3/2014, 2:03 PM
Common practice is to use brightness and contrast to conform levels. Then after that use other tools in the kit to adjust colour. You can do it other ways but this is the fastest and what you will see stated in editors text books on the process of correction, which is the first thing that needs be be done. I've tried correcting in Levels and by using curves, they work, just not as quick.

musicvid10 wrote on 5/3/2014, 3:11 PM
Whatever tools one uses, leveling must take place last in the chain. We need the output to conform, not pre-edited source.
VMP wrote on 5/3/2014, 3:16 PM
Thanks all.

Paul_w that's assuring to read :-).
Instead of blowing out, I usually tweak down the brightness using that FX which boosts the contrast while retaining the conform levels according to each shot. I shoot with flat setting.

Also to roll of the luma before adding any limiter works fine with the B&C FX.

Thought the levels are very handy to use while grading.
I am looking forward to start a new thread soon regarding advanced grading with Vegas. I am sure you can get some nice looking Technicolor like look with the colorwheels from the first and secondary color corrector combined with level curves.

The Aviator Technicolor grading

Screenshot from The Aviator Technicolor grading

Color palettes from 36 of your favorite movies

paul_w wrote on 5/3/2014, 3:36 PM
Good stuff. Yes there is a lot you can achieve within the default plugins in Vegas without any external special grading effects. Brightness and Contrast along with Colour Correction (for saturation etc) are the goto tools. What is important is of you make a change to a grade, then you always go back to the start with Brightness and contrast and re-adjust levels. This is perfectly normal and you may need to do this a few times. So the actual chain position is not important when you know this. If you want to go beyond the standard conforming and colour grading ability of Vegas, then you can call in the big guns and go further (at extra cost) like making Power windows etc.

musicvid10 wrote on 5/3/2014, 6:19 PM
Do all your editing in native rgb space, when done slap a levels filter on once, render, and be done with it.
Why add extra steps when it is that simple? And yes, the hierarchy makes a big difference. We want levels to be post-, not pre-process.
paul_w wrote on 5/3/2014, 9:56 PM
yeah, we're talking here about correcting and colour balancing clip by clip, rather than the whole TL. Clips with varying exposure and colour balance. So we have to apply corrections to each clip. Its always luma correct first then colour balance and lastly apply any 'look and feel' grade to the whole thing if needed.
I guess there could be variants to that but thats the general rule. You can mess with reversing the order of B/C and CC filters and it also works, not sure what noise implications there may be in doing that but it does work although it adjusts differently in terms of the reaction of the fx effecting one another.
Guess theres more than one way to skin a cat as they say...
musicvid10 wrote on 5/3/2014, 10:09 PM
"Its always luma correct first then colour balance and lastly apply any 'look and feel' grade to the whole thing if needed."

Nope, you've already put yourself in a straightjacket with the first step. Output luminance (not "luma") goes last. There is no logical reason to conscribe the domain of available source levels during the editing or preview phase, and plenty of good reasons not to.

Correct EACH clip to suit your tastes until you are satisfied with the results of the whole project, as viewed in Vegas' native RGB preview space.

A typical project may have several hundred scenes, from different cameras and lighting. Fix them, until they look right individually and in sequence Then, when finished editing, apply the levels (or curves) filter to the OUTPUT FX, also called the Video Bus. That's the one at the top of the preview window.

Render. That's it, really. You are far more likely to lose bit depth by forcing output leveling at any other place in the processing chain than at the output. That's the math. Plus, consider the inordinate amount of time involved making all those individual luminance adjustments, then re-doing them, and then, . . .

The simplest, failsafe, wysiwyg workflow in Vegas is, "Edit RGB, Render YUV."
I didn't say that was intuitive. But, not only is it compliant, if everything else is done correctly, it is suitable for PBS broadcast. Other methods simply cannot claim that.

paul_w wrote on 5/3/2014, 11:13 PM
I guess yet again it seems we have to agree to disagree regarding the filter order. :)

As for Luma adjustment, yup. Luminance in the perceived brightness by the human eye whereas Luma is the video level term given to the non linear representation of luminance. After applied gamma if you like. We use the term Luma for video level adjustments (hence controls like Luma Curves etc.) And Chroma being for colour. Both of which are separate controls of course but can affect each other if adjusted to a large enough amount.

But to be honest i think that is taking the thread away from the OP's point.

Its 5am here in the Uk, think i'd better get some sleep! Or maybe just get up.. Oh well. Will check back tomorrow. Cheers.


musicvid10 wrote on 5/3/2014, 11:26 PM
Vegas displays luminance level scales. As an RGB editor, Vegas does not display or offer direct user control over luma,, which indeed is gamma-weighted.. "Luminosity" in the functional imaging context does have a subjective component, so perhaps that's where you're getting confused. So when discussing Vegas levels, it is correct to do so in terms of luminance. The display in the histogram above is Luminance-RGB (not Luma-R'G'B').
Luma versus luminance
NickHope wrote on 5/3/2014, 11:47 PM
VMP, Brightness & Contrast is not inherently more destructive than Levels or Color Curves. Including these different tools allows the user to work in different ways depending on the nature of the required correction and the user's working preferences. It's good to have options. The benefit of Color Curves is that it gives you fine control, but at the expense of being relatively difficult to use. Any of these FX can of course be destructive if they're used wrongly. To use them effectively it really helps to use and understand the video scopes.

Paul, if you conform your levels before your colour, you've generally got less information to do your colour correction with. So in general I think one should correct colour before conforming levels. That is especially true if your levels procedure involves "lossy" hard limiting. If it merely involves a linear conversion, such as a "Computer RGB to Studio RGB" preset, then by my reckoning it might not really matter whether you do levels or colour first and I expect the result would be very similar.

Me, I do them all at the same time, usually in a single colour curves FX at event level. But then I'm a masochist. My projects, which are mostly underwater and require lots of adjustment, are full of things like this:

or this:

musicvid10 wrote on 5/4/2014, 12:10 AM

Actually, the Computer->Studio levels effect does reduce usable bit depth, by nearly 16%. So adding it early in the chain limits the range of available colors for editing and grading, tending to compound such losses later on (i.e., the relationship is geometric, not arithmetic). Saving the inevitable bit loss until the very last step has distinct quality advantages, which should be obvious to paul_w by now. Plus, the inevitable slopover in luminance and color channels would simply not be tolerated by many digital broadcasters.

Here's an extreme example of deliberately compounding range compression with expansion. This was done in lieu of a native posterization filter in Vegas. Doing it in the reverse order has no such effect.

NickHope wrote on 5/4/2014, 12:20 AM
I understand. Thanks for clarifying musicvid!
paul_w wrote on 5/4/2014, 6:29 AM
Hi guys. This is how Premiere Pro does it, or at least one way to do it. It also has a Fast Colour Corrector tool which combines Levels and a Colour Wheel adjustment, thats the other way.

Notice the use of the "Luma" corrector which is essentially brightness, contrast and gamma. Followed by a colour corrector. This is the way i do it in Vegas. Why Vegas referrers to it as Luminance is just plain weird. Its not, we are adjusting Luma!. Same as in Premiere Pro. Also just cross checked this against 'The Colour Correctors Handbook' and sure enough, its stated as Luma we adjust within any NLE. (or should be - naughty Vegas).

Another point is i am not using any Levels effect anywhere in the chain and no hard crushing either. Its purely careful brightness and contrast followed by colour correction. You get the same result and bit loss as any other levels and curves if adjusted correctly. Obviously any crushing means data loss. But that goes for any corrector. And yes if you swap them around, you can achieve the same result.

I do it this way, in this order, because its the way i learned to do it from various colour correction books over the years including the one mentioned. Its standard practice. Luma correct , Chroma correct, then final Grade. Theres no reason not to do it this way, but of course like already said - there are a few ways to achieve correction, its not written in stone or anything. Nick, using curves is great too. You can correct luma and chroma in one go while staying legal. I just find it faster to use sliders.

We are talking personal preferences here not hard rules.

edit: a few add on comments:

"VMP, Brightness & Contrast is not inherently more destructive than Levels or Color Curves"... yes, i agree.

"The benefit of Color Curves is that it gives you fine control, but at the expense of being relatively difficult to use"... my experience also. And why i choose sliders.

"Paul, if you conform your levels before your colour, you've generally got less information to do your colour correction with. So in general I think one should correct colour before conforming levels. "... Thats a fair comment. But its against the normal way of doing things 'out there'. But i accept the thinking here. If we were in conformed 709 from the start like in PPro or FCP, it wouldnt make any difference. But we are in Vegas with its 0-255 space :(

Last edit:
Guys i'm going to be taking a break from the forum, so apologies if dont respond anymore. Was up real late last night reading and researching about this and got into trouble with my partner (not a happy bunny). So need to give it a rest now. Just saying. Thanks and i will doing some tests using before and after correction. Bank holiday this weekend and i should be outside taking advantage it. Preferably with a camera in hand.

musicvid10 wrote on 5/4/2014, 9:21 AM
Paul, I can see more clearly now that a large part of your belief system comes from what you have learned and experienced while working with other programs, mostly Premiere I take it?

I also realize your frustration from trying to transfer everything that makes sense in that environment to this program. I don't know anyone who's succeeded with that approach. And I know it's hard to start with a clean slate when we already take so many things for granted. So does someone who is just realizing this beat his head against a wall and insist that Vegas work like Premiere, or just use Premiere?

We already know that Vegas works differently than Premiere. Vegas edits in native RGB color space. Y' (luma) gets converted to Y (luminance) values. Hierarchy of plugins affects bit depth, among other things. Vegas has no automatic correction of preview-to-playback levels. And the list goes on. All of these things have been clearly demonstrated by now. I get frustrated when working in Premiere. Everything seems backwards after having left it for Vegas fourteen years ago. And predictably, reading about it doesn't help.

Plenty of threads in which to discuss the merits of Premiere vs. Vegas. But wishing it so will not make Vegas behave the way you are accustomed to or expect. Like its geographic namesake, Vegas plays by a different set of rules.
"Should," however, is an entirely separate discussion.
Have a good rest.
Marco. wrote on 5/4/2014, 2:07 PM
Paul, I learned the same way: First luma, then chroma. My resources at least suggest to do that way unless there is a specific reason not to do. From the loss of information (when working in integer math's bit depths) it doesn't really matter, you also lose them when color correcting.

Actually I don't know how much difference an inverted order would make, I just copied the given workflow, which is the faster one. What they say and what I see is correcting luma will always also affect color saturation and in many cases after having done the luma correction, the amount of color correction needed reduced a lot (or even wasn't needed anymore).

Though I prefer using Levels instead of Brightness and Contrast for luma control, because it is easier to separately control black and white level and it also offers gamma control.

And it looks like we learned same about the use of the terms "luma" and "luminance". Whereever we talk about gamma corrected, nonlinear sumed RGB values I learned to call this "luma". I doubt Vegas Pro does revert the power function for its internal processing into linear range in 8 bit projects. I'd assumed Vegas Pro processes R'G'B'.

I just saw in two of my cc books both Steve Hullfish and Alexis von Hurkman suggests to first optimize the tonal range before adjusting chroma but I also see there are different workflows used by different experts.