You might think about a compensating developer to give yourself a bit of safety with highlights. But it sounds to me like an issue of metering. Another thing is that my people (=fair skinned) tend to show blemishes very easily, and for that you may want to filter in the direction of red.
Fair hair is hard in uncontrolled top light, it blows out very easily. A bit of fill (reflector or flash) should allow you to boost the ambient light and thus meter in such a way as to keep the hair in range. A warm reflector would be nice. Wish I had one following me around always
Even with not so fair skin and hair, it's hard to control proper exposure in broad daylight. I even had a situation where reflection on nose or part of forehead caused issues and she wasn't white skinned.
I understand you are shooting outside but are you shooting in broad daylight in sunny areas? That would cause problem with any type of subjects. How about finding a nice softly lit area where it is in shadow but lit by light reflecting from nearby objects? (ie. open shadow) Or use a reflector to create your own? Or use a scrim if you must? I think your problem isn't really your exposure setting of your camera but an excessive contrast created by too harsh of lighting. (ie. direct sun light)
The palm of my hand meters +1.5EV brighter than an 18% gray card. If you metered the skin of a fair complexioned person from the north, and only gave the exposure +1, their skin was actually overexposed by +0.5EV (assuming their skin was as light colored as the palm of my hand). The RIGHT way to expose would be simply to meter an 18% gray card or to use an incident light meter, with the exposure setting on camera exactly as suggested by either meter, and the skin would then show up +1.5EV brighter than the 18% gray card in the photo!
wiltw is on the right track,but was diverted to a siding.
No matter the ethnicity of a person, meter their palm, place it on Zone VI and their skin should record correctly.
More than 30 years ago two friend and I experimented with this. I am Caucasian, one is African American and the other Hispanic.
We tried varying lighting conditions, and several films. The objective was to make it easier to get proper exposure of each individual in a multi-ethnic church congregation regardless of the light. It was successful.
[FONT=Comic Sans MS]Films NOT Dead - Just getting fixed![/FONT]
Metering off the palm of your hand (with your hand in the light that the subject is in!), then opening up +1 stop will assure you get the skin tones placed properly.
However in days of yore, LF photographers would shoot a few Polaroids to make sure they nailed the exposure, then take their final exposure on their 4x5 or 8x10. I've done the same with my d*g*t*l P&S and my 35mm in tricky lighting situations. I've taken several exposures with varying exposure compensations on the P&S. Once I nailed the amount of exposure compensation I wanted on the P&S, I dialed in the same compensation on the 35mm and took the shot, knowing that the exposure on film would give me the look I wanted. Basically the d*g*t*l P&S served as my Polaroid before committing the shot to film.
1) Place your subject in the shade
2) Use diffusion to reduce the high contrast light from the sun.
3) Use reflectors to reduce the imbalance between direct sun and shade (although this can make subjects close their eyes, due to the brightness of the reflector).
Combinations/permutations of all three may produce the best results.