Back in the dark ages when I was young, people with cameras would love bright, sunny days. It's not surprising; lenses were slow and so was the film emulsion. You had to take what you could get, especially in the higher latitudes. Family snaps from that period usually show people squinting into the sun, but with reasonably well-exposed faces.
I think many people have carried this behaviour into today's world - despite the faster sensors and better lenses. They shoot in bright conditions - but don't always get the results they're hoping for. The reason is the nature of the light on bright, sunny days.
Check out these two images from the Perth Zoo.
Elephants at Perth Zoo.Elephants at Perth Zoo - photographed in harsh light. Tricia the elephant at Perth Zoo.Tricia the elephant at Perth Zoo in soft light. Ok, neither will win the Wildlife Photographer of the Year; they're just snaps, but they show the effects of shooting in bright light. The first image has completely blown-out highlights and deep shadows; and it was shot with my Nikon D800 using raw. (Had a been shooting JPEGs and/or a less capable camera, it would have been worse.) The second shot is quite nice. It has a good tonal range because everything is within the capacity of the Nikon to record the light.
What's the difference? The first was shot on a typically hot, clear, bright day in Perth. The second was made on an overcast day. In one, the sun is creating contrast ratios beyond the capacity of the camera's sensor (which has a very good capacity in that regard). In the second, the cloud is producing softer light and lower contrast ratios which are well-within the camera's ability. What do I mean by "contrast ratio"? It's the range of light levels from the brightest to the dullest part of an image. Modern sensors are good, but they still can't match our eyes in this regard.
If this is an issue when photographing an elephant, it's much more so when photographing family and friends?
So, what do we do? We can't dial-up cloud on demand.
We have a few options. Time of day can help. Early or late in the day provides a softer (and warmer) light which is kinder on the skin and won't throw deep shadows under eyes and noses. Getting technical, the lower light levels also make it easier to produce a show depth of field and a nice soft, creamy bokeh in the background.
Orangutan at Perth Zoo.Orangutan at Perth Zoo.
This image of one of the Orangutans at Perth Zoo was made under very heavy cloud. Note the nice even light on his face, and the bokeh produced by a combination of the wide aperture and long lens needed to get this close-up.
Even if you have no choice but to make a portrait or group shot around midday, you can still do a few things.
Stand people in shade. They will feel better (especially if it's hot), will be less likely to squint into the light, and you will get a softer (if somewhat "cooler") light with better skin and few if any deep shadows.
If you're really keen and are prepared, you can use a diffuser. These can be anything from a purpose made unit [link] to a white bed sheet or curtain and are held between the sun and your subject to give a softer, diffused light.
Take a lead from the animals at the Perth Zoo. They move around when the sun's soft. But when the sun's blazing and throwing hot and hard light, they get in the shade and take it easy. Do the same with your subjects, whether they be family, friends or animals or plants. They (and your images) will do better on overcast days, or in some gentle shade.