Gina Freeware is a simplified version of Gina - Skin Tone Correction.
Gina has just three sliders: Tone, Saturation and Glow. But before I talk about them, I need to talk about skin tone (at least as far as Gina is concerned). Gina is balanced for skin that, technically speaking, is pale and slightly more yellow than magenta. This type of skin is notoriously hard to photograph well, especially with digital equipment. There are several reasons that this is so, and basically it comes down to the camera capturing more infrared light than it should, a problem that flash can exascerbate.
Infrared light registers as red on your camera, and any areas of the skin that are particularly reflective to infrared light are going to photograph as more reddish than you can see with your eye. These areas are particularly: veins, blemishes, blotchy/blush areas (even when they don't look blotchy right now), the tip of the nose, upper cheeks and the centre of the forehead. (Interestingly, subjects with substantial skin pigment, no matter what tone it is, don't generally have this photographic problem -- the pigment absorbs most of the IR -- so you won't need Gina for those shots.)
These reddish areas are only a little obvious on the screen, but really stand out when printed -- many people don't like their photograph taken because often prints of them look too red, and they look sunburned or blotchy.
Gina can fix that, and make your portraits -- even ones taken with inexpensive cameras in bad/flash lighting -- look good, perhaps even great. Well, at least keep your subjects from going "ew, I look horrible!" And that's very, very important, especially when your subjects are your family.
Skin tone correction isn't a professional secret, but it is something that pro photographers have to deal with on a daily basis. The same correction that used to require playing with curves or fiddling around with lots of sliders in HueyPRO or (worst of all) using Some Other Program to fix can now be done in five seconds with one slider -- with Gina.
Gina has a simple user interface and is easy to use.
When checked, the plug-in can affect the image. When unchecked, disables the plug-in.
Resets all plug-in values to startup defaults. Useful for getting back to a sane place after experimenting wildly.
Reveal the plug-in version number, author and homepage.
Number one thing to remember about using Gina: go easy on the sliders! If a photo looks doctored, you've gone too far.
Adjusts the skin tone -- this is Gina's main control. 99% of the time, you'll move this slider to the right, not the left. Left adds red, right subtracts it. Move this slider one "click" at a time -- click to the right of the pointer. Don't just grab it and haul it over to 1.0, unless the "embalmed" look pleases you. I suppose if you're taking pictures of someone who's queasy and "green" you might move it to the left, but I haven't seen a case where this is necessary. You can certainly add sunburn if you want, but most people want to look tanned, not burned!
Adjusts the saturation (colour intensity) of skin tones. Generally you won't need to mess with this unless you've got camera or exposure or conversion problems. Still, a little bit (0.1 or so) can help someone who's looking pale.
This is a fancy trick -- it adds subtle amounts of light to the shadow tones of skin. At higher values, it increases the overall brightness of skin tones. Visually, it acts as if someone was shining a light through your subject's skin, making it look brighter than it would from just reflected light. It can really make simple portraits look lush.