Setting Exposure

[Simon Denny]

I would like to here from others how you set your black and white levels?
What procces do you go through?
How do you correct for skin color?

Because Vegas has so many ways to do things im trying to find the best way to do all of the above and now im really confused again. When i look at my corrected footage Im starting to guess that i have things right but now im not to sure.

In wish Vegas had a plugin that you could raise/lower blacks,mids,whites...
I like the way FCP can do this with exposure.

Cheers
Simon

[Glenn Chan]

A tutorial on using levels:
http://www.vasst.com/resource.aspx?i...0-90d2f8de9fc1

Vegas' color corrector and secondary color corrector is similar to FCP's. (Though a little different... in Vegas you have to "juggle" the controls if working in studio RGB).

[Simon Denny]

Thanks Glenn,
What about using color corrector and desaturate to get black & white image and then look at the image contrast and do levels from here?

Simon

[Jon Fairhurst]

There's a B&W plug. Insert that as the first link in the chain. Check it on when setting the luma curve, then check it off when returning to full color.

[Simon Denny]

Hi Jon,
I have been doing that for a while but have been using desaturate in the 3 wheel color FX with some succes.

Cheers
Simon

[Daniel Alexander]

Hi Glenn, we spoke before about the different settings in vegas in regards to studio rgb where you mentioned if i am working in native hdv and my output is mainly for tv/dvd, i should be in 32bit mode, 2.222 video gamma and uncheck studio rgb. Is this the same for the mxf format (PAL) coming from my sony ex1? Is studio rgb just for when your output is for computer viewing only? Thanks

[Glenn Chan]

Daniel:

1- It's easier if you start your own thread for your question... this makes discussions easier to keep track of.

2- To answer your question, there used to be a clear logic as to which formats used studio RGB and which formats didn't. In 8-bit projects, video-world formats like DV, DVD, HDV, SDI, etc. use studio RGB levels. Computing-world formats like JPEGs, still images, etc. use computer RGB levels.

In 32-bit the previous logic doesn't work... consult the table in my article.

2b- The EX1 probably behaves like other MPEG-2 footage in Vegas. So in 8-bit it's studio RGB, in 32-bit it's computer RGB.

[Glenn Chan]

What about using color corrector and desaturate to get black & white image and then look at the image contrast and do levels from here?

I don't really find that necessary. The waveform monitor (if you turn off the composite mode, and use the "luminance" mode) can look at the signal without the chroma component.

Plus, the viewer will be looking at a color image anyways so you should be color correcting a color image in my opinion.

[Simon Denny]

Hi Glenn,
I'm think of getting Vegas+DVD, Vol. 4, Color Correction in Sony Vegas (DVD)
Is this a Pal version?

Cheers
Simon

[Jon Fairhurst]

Originally Posted by Glenn Chan

Plus, the viewer will be looking at a color image anyways so you should be color correcting a color image in my opinion.

Hi Glenn, I used to think that was true, but when you adjust levels the saturation will look wrong. By removing the chroma, you can get the luma scale you want without running into ugly colors that might scare you away. You can always toggle B&W on and off to get the right balance.

We've been using this order:
* B&W (toggle on and off when setting levels)
* Levels (for setting the luma color curve - usually some sort of S-curve. Look at the histogram to get the limits - 16-235 - right.)
* HSL (for bringing the saturation in line with the luma curve)
* Color correction for setting the right tone.

One advantage that we've found is that by setting a nice S-curve, the color correction is less prone to contouring. We've been working in 8 bpc mode, rather than 32-float.

[Glenn Chan]

I'm think of getting Vegas+DVD, Vol. 4, Color Correction in Sony Vegas (DVD)
Is this a Pal version?

It is NTSC. I don't believe there is a PAL version.

I'm not sure if this helps, but you can likely play a NTSC DVD on your computer without problems. (Sorry, I live in a NTSC country so I might be a little insensitive to those in PAL countries!)

[Glenn Chan]

Hi Glenn, I used to think that was true, but when you adjust levels the saturation will look wrong. By removing the chroma, you can get the luma scale you want without running into ugly colors that might scare you away. You can always toggle B&W on and off to get the right balance.

In my opinion, that just isn't necessary. You can bounce between your levels/curves and saturation to get what you want. You don't need to be looking at a black & white image.

As far as luma/chroma goes, only the color corrector filter can adjust one without affecting the other. The black & white filter and the HSL filter use different maths, so they affect both luma+chroma at once (not equally, but those filters affect both at once).

[Jon Fairhurst]

Originally Posted by Glenn Chan

In my opinion, that just isn't necessary. You can bounce between your levels/curves and saturation to get what you want. You don't need to be looking at a black & white image.

True, bouncing between the two works. Personally, I like looking at the B&W image as well.

The main point is that after adjusting the s-curve with the levels control, the chroma saturation might be very, very wrong. If you don't look at the B&W image and/or ride the saturation control, a very nice luma curve could produce a horridly over/under saturated result. I've been guilty of this in the past - I make an ugly picture and back off, when the problem might be a secondary, rather than the primary, control.

Regarding the math in the B&W vs. HSL adjustments (in 8bpc), they are different? Can you offer more detail?

Y' = 0.587 G' + 0.299 R' + 0.114 B' in both cases, right? (The primes indicate gamma corrected domain.) Both the B&W and HSL saturation control should simply reduce the U and V channels, right? If I take U and V to zero with either filter, the result *should* be the same.

If not, I'd love to know the specific difference.

Thanks!

[Glenn Chan]

The math for HSL is here:
http://en.wikipedia.org/wiki/HSL_and_HSV
L = (MAX + MIN) / 2
MAX is whichever of red, green, and blue are the highest.

Try this:
Add the color bars generator.
Stick on the HSL adjust filter. Set saturation to zero.
You'll notice that all the bars have the same shade of grey. This doesn't happen with the Color corrector. You'll also see that the HSL affects luma values if you look at the waveform monitor (pick the "luminance" mode).


Black&white filter takes the average. (R + G + B) / 3

[Jon Fairhurst]

Wow. Thanks Glenn. I'll check this out.

Having designed various hardware encoders, decoders, input and output modules in my career, I'm stunned when the standard YUV <=> RGB equations aren't used, and aren't noted in the UI.

Y = (R+G+B)/3 is crazy talk! ;) ;) ;)

This reinforces why we should always shoot color and then choose how we desaturate in post. That leaves us the most options. And you never know exactly what the camera might do with it's B&W equations.