What Umbrellas Do
Why everyone needs an umbrella (Re: photography)
1. One direct flash at 28 inches (a random distance, seemed about right).
Harsh - the usual sharp dark shadows. No fill or reflector used here. Some reflections on the eggs. The contrasty light shows the detail of the imperfections of the egg shell surface (this example is like human skin imperfections and wrinkles). Note that a speedlight flash head is a very SMALL diameter light source.
So this is the problem.
2. One 40x32 inch double diffused softbox, fabric at 18 inches.
Note the reflections on dish in front of eggs are reflections, not shadows. The shadows are soft and vague (under dish, for example). The large light source wraps light around the eggs and under the dish. The way it does that is because the 40 inch softbox (or umbrella) is 18 inches from the 7 inch dish (big and close), so light comes to the egg from the left and from the right, and from every which way, which fills its own shadow. This is how large light sources work, by being close in order to become relatively large. And large is what makes soft. The softness smooths skin, which is good for portraits.
There are mirror reflections of these eggs on the dish (shiny dish), but notice the soft light wrap also lightens the dark canyon between the eggs. This is a day and night difference, in several respects.
Another Flash Basics page details the definitions of Soft Light.
3. One 45 inch shoot-through umbrella, fabric at 18 inches (its nearest center point was 18 inches).
Very nearly the same and equal light quality as the softbox (both are 40 inch size at 18 inches). I would say equal light quality, especially for a reflected umbrella at same distance, but the curved shoot-through umbrella edges are not as close as the flat softbox edges at this close distance, so it acts a bit smaller. The main difference is the softbox light is more contained frontally, and the umbrella has wider side spill, and a shoot-through umbrella has extreme spill out the back side. Two thirds of the light goes out the back of a shoot-through, spilling all over the room. Up close at 18 inches however, we really don't care, but at say five feet, it would extreme to deal with (when direct subject and rear spill reflection paths may become more equal strength).
One egg from the first "1" Direct and from this "3" are enlarged below. In "3", the egg shell texture is smoothed (no shadows to show surface texture or imperfections), and especially notice how the light literally wraps around the left dark end of the eggs (more than in 1 because 3 is large, and more than in 4 and 5 because 3 is close). Imagine this contour was a nose or chin or cheek on a face. This "smooth" and "wrap around" is what soft light is, and large and close make it happen. Just open the umbrella, and set it close.
The softness smooths skin, which is good for portraits. Shadows enhance wrinkles and skin pores and blemishes, makes them more visible. Shadowless soft light hides them, no shadows to show them. Seems to me that no matter how technically and artistically great your photo may be, if it shows their wrinkles, the ladies won't like it.
And this is just one light. Two umbrellas can essentially eliminate all shadows. A second fill umbrella near the lens axis really helps minimize wrinkles.
Umbrellas definitely are equally as soft as softboxes. No actual difference. The size and closeness is what makes soft. If it is 40 inches size at 40 inches distance, it matters not if it is a softbox, a umbrella, a white reflector board, a white cloth diffusion screen, or a white reflecting wall surface. If the size and distance is the same, the light is pretty much the same. This size and closeness determines the angles of the multiple self-filling paths, creating the soft properties.
Catchlight reflections in human eyes will look different from umbrellas and softboxes. This eye picture is with a reflected fill umbrella at 4 feet. It is not normally viewed this large, and it is hard to see the detail at any regular size. However, shoot-through makes it closer and larger to exaggerate it. A softbox catchlight is rectangular, which we imagine to look like a window reflection.
4. One 45 inch reflected umbrella, fabric at 40 inches (a distance not exceeding the umbrella diameter by much).
Almost as good, and 18 inches is not always practical. The greater distance fills less well than if it were closer, the shadows are slightly darker, but the difference is subtle. The umbrella shaft does prevent it being as close as shoot-through can be, but reflected is a wider light for larger subjects. As close as possible always applies, and the umbrella "diameter" is a typical close distance for portraits - the sitting subject typically can reach out and touch the light stand pole of the main light (not the fill however, it has to be more back with the camera to be out the way of the lens).
5. One 45 inch reflected umbrella, fabric at ten feet.
Shadows sharper and darker yet - still better than a direct light, but fading fast. The light source is becoming small at ten feet, and this hurts softness. But groups do require a greater distance, for the wider width of the light beam to cover them. However closer is always better when it is possible (closer to be a relatively larger light source). Do not place the umbrellas at ten feet for a head and shoulders portrait. Ordinarily should be about as close as possible. However too close means the light falls off fast behind the subject. 12 or 18 inches will have little depth behind, but 30 or 40 inches is pretty reasonable.
Note that a 40 inch light at 10 feet is the same angular "size" as a 12 inch light at 3 feet, or a 4 inch light at 1 foot (all fill about 19 degrees of view from subject). Large is what makes soft. Close can make large. Both large and close is even better.
One speedlight directly bounced on ten foot ceiling. Flash was pointing up about six feet distant from the eggs. The light is more even, and has much appeal, but it is coming from overhead. Which is sometimes appropriate, but maybe not best for portraits, at least not without some forward fill (a small bounce card works).
This ceiling is more than 7 feet above the eggs, but the ceiling is larger than the umbrella to compensate, and a large light is what works. Bounce flash is an extremely powerful general purpose tool. The large ceiling is like a large umbrella, but umbrellas are easier to aim than ceilings. Bounce Flash is pretty important.
For comparison, here is an animation including all six frames above
The flash used above was a Nikon SB-800 speedlight in a 45 inch white umbrella, except frame 2 with softbox was an Alienbees B400 studio light. The first four frames adjusted power level to f/11. Frame 5 was f/5, and frame 6 bounce was f/7, both at full power ISO 200.
Play with this yourself (umbrella at the distances above), to see it for yourself, to become a believer. Nothing is ever as dramatic as seeing our own result. An umbrella is an inexpensive tool that makes a huge difference. The best way to use umbrellas is: large and close, early and often.
There are more sample pictures similar to the above, as part of another section pertaining to understanding flash basics. That Fundamentals Part 3 is about soft light.