How to use vectorscope and hue tools to check/correct skin tone?

[SteveFogel]

Hi, all... I'm a photographer and videographer, and total Affinity Photo newbie. Been using Capture One and PhotoShop for years. I'm used to using scopes (WaveForm, VectorScope, etc.) in video post-processing and I'm delighted to see that Affinity Photo has a vectorscope for accurate color and that it has a skin tone line.

Would someone please explain the procedure for using the vectorscope to check and correct skin color, like I would do with, say, DaVinci resolve?

I want to:

1. Isolate the face and have the vectorscope show just the colors of the face

2. Check where the colors are against the skin tone line in the vectorscope

3. Select the face and use hue and saturation controls to fix the face color so that it aligns with the skin tone line.

What are the steps and tools? Thanks!

Steve

[NotMyFault]

4 hours ago, SteveFogel said:

1. Isolate the face and have the vectorscope show just the colors of the face

2. Check where the colors are against the skin tone line in the vectorscope

3. Select the face and use hue and saturation controls to fix the face color so that it aligns with the skin tone line.

 

Hi and welcome to the forum, SteveFogel.

1. the vectorscope depends on the colors in the rendered image. As faces other areas with human skin are normally the only areas of this color, normally there is no need restrict the diagram to specific areas. If you need, you must create a mask so that other areas are not shown.
2. well, the vectorscope does exactly this, it shows where the colors in the image are as light colored points. Look at the scope panel.
3. Use any of the selection / masking tools which works best for the actual image. You can select by color/hue, lightness, or use a brush to define areas. Then add adjustments which work best for you, e.g. hue, curves, selective color and adjust them, and try to get the scope to match the I line. You may go hardball and use the gradient map, this will remove any natural hue/sat variations and enforce advertisement colors.

there are tons of tutorials in youtube guiding you through the process. Search for 

skin tone vector scope affinity

 

btw using the I bar for color grading is discussed controversially, so some argue to use other appraches.

[Alfred]

1 hour ago, NotMyFault said:

there are tons of tutorials in youtube guiding you through the process. Search for 

skin tone vector scope affinity

https://www.youtube.com/results?search_query=skin+tone+vector+scope+affinity

[SteveFogel]

Thanks to you both. How do I enlarge the vectorscope? I can drag to make the vectorscope window larger, but the scope itself doesn't grow. Thanks!

[Ldina]

@SteveFogel Steve, I'm not sure if you can enlarge the actual vector scope graphic. If so, I haven't found a way.

One thing I often do when skin tones are an important element of the photo is to switch from RGB to HSL samplers in the Info Panel. That "I" line (i.e., skin tone line) in the vector scope corresponds to a Hue value of about "18" (red, with some added yellow). Skin tones vary from person to person, and even in the same person in the same photo, so a Hue of 18, plus or minus about 5 points either way, is a good general starting point. Relying on a single sample point doesn't always work well, so I prefer to run my cursor over nicely lit skin midtones. Highlights and shadow often skew away from that "I-line" more than midtones.

Redheads and young pale children often lean a bit toward the red side of 18 (13-18), and people with a rich tan tend to be more yellow (18-25). Those are just ballpark numbers. Saturation and Lightness make a big difference too, but this is a good starting point. I do use the vector scope, but I often rely even more on HSL readouts in the Info panel. I also like CMYK readouts for skintones, and when dealing with portraits, I often set both HSL and CMYK samplers in the Info Panel. I suspect you know this already, being an experienced videographer and longtime photographer, but I figured others may read this and find it helpful.

[SteveFogel]

Actually, I wasn't aware of the I line equivalent in HSL. I just tried it on a portrait that I shot recently and the skin hue varied between 17 and 18. Very good to know! Thank you!

[Ldina]

@SteveFogel Steve, I'll add a few thoughts about using CMYK for skin as well. This applies to skin "Midtones", not to bright highlights or shadows.

A good general rule is that Cyan should be approximately one third (¼ to ½) of Magenta and Yellow, with yellow equal to magenta, or slightly higher (but not excessively so). For example, for Caucasians, a good starting point is about 10C, 30M, and about 30-35Y or so. Again, this is for well lit skin MIDTONES. Highlights and Shadows will vary quite a bit. (RGB is generally useless for assessing skintones). 

Redheads, young children, etc, will tend to have yellow and magenta close to equal, but yellow will rarely be less than magenta (except for rouge makeup or cold wintery cheeks). Someone with pale, light skin might have values of 5C, 18M, 18-20Y or thereabouts. Dark races may have more yellow (Asians, Latinos, Africans, Middle Easterners, etc), but sometimes they have more red. If you have too much Yellow combined with higher Cyan values found in darker skin, faces tend to skew toward green (never too attractive, unless you're a Martian). Due to their darker skin, they may also have a Black (K) component. Shadows and highlights tend to vary, but it's good to guard against too much saturation in shadow tones. 

Anyway, I like seeing both HSL and CMYK readouts when working on portraits. Each offers a different perspective. Sometimes HSL tells me what I am missing, but sometimes CMYK does. For example, it's easy to end up with a value like 0C, 30M, 32Y, which is definitely RED. It's too saturated and needs some Cyan for balance. That's where I like looking at CMYK. Together, they keep me on track. FWIW..