cgardner
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 p.1 #4 · soft box for of camera flash units | |
Trying to do studio-style, large diffuser lighting is like trying to pound nails with a screwdriver: it can be done, but isn't the best tool for the job. So all things considered if you want to do studio lighting you'd be better off buying studio lighting gear and leaving the Canon flash for the lighter, more mobile lighting tasks. That's not said to discourage experimentation, but rather to prevent the throwing of money at solutions which could be better spent elsewhere to meet your goal of doing portraits.
Your first mistake is assuming you need a soft box. That's a bit like going the doctor and telling them what to prescribe rather than letting them prescribe a solution. If you want to use a single tethered light and a reflector a modifier like the PhoTek Softlighter would be a better choice than a 28 x 28 softbox because it is larger, will wrap the light more, and because its basically an umbrella with a cover on it will diffuse the light better because 100% of it is forced to change direction, not blast straight through a piece of diffusion fabric.
If you plan on using two flashes in a key / fill arrangement it is possible to get similar soft looking lighting with smaller modifiers. Something on the order of the 28x28 Westcott is ideal. The guy who taught me how to get soft looking light with two direct flashes, Monte Zucker, later used and endorsed the 28x28 Westcott for studio work in his later years. The size of the modifier used for the fill is less critical if it is kept center where it cast few shadows. But a problem with big modifiers on Canon flash is that the control of the slaves is done via visible light pre-flash from a 580ex (not IR or magic) and modifiers block the sensor making radio triggers necessary. That means spending as much on the triggers as on the flashes.
If your goal is better lighting for on the go candid portraits and general editorial / PJ style shooting you could get by quite well with a pair of Canon flashes and simple reflection / diffusers:
http://super.nova.org/TP/DIYdiffusers.jpg
I have both hot shoe and studio lights and use the hot shoe and diffusers when I need a portable solution and use the studio lights when I can get the subjects to the studio. Admittedly I'm lazy but can afford to be because I do photography for amusement, not to make a living. But still I find it easier to do the job with the proper tools. One day a few years ago when visitors dropped by I grabbed the camera with 580ex attached and shot a dual flash photo of the boy below, then decided to switch to the studio lights.
http://super.nova.org/TP/DIYvsSB.jpg
That comparison illustrates you don't need huge modifiers to get soft lighting if two lights are used. I find that is a much more practical way to use Canon flash with its built-in wireless. Note how the upward orientation of the flash head keeps the sensor clear and also causes 100% of the flash output to change direction? That redirection of the light is actually quite similar to how light is scattered in a softbox and size-for-size offers more diffusion than simply blasting the focused flash through a sheet of fabric.
By better understanding the underlying cause and effect you will make more effective purchasing decisions.
Softboxes don't work the same way on hot shoe flash as they do on studio lights due to the difference in flash tube location. Studio lights have bare flash tubes which stick out in the box radiating (and diffusing) in all directions, while the hot shoe focused with fresnel lenses just blasts all its light forward. Also something to consider If using two or more lights with Canon wireless a pitfall is that they are not designed for use with modifiers and modifiers will block the sensor on the slave. A 580ex master uses visible pre-flash, not IR, for communicating with the slave. That's why people find it necessary to use radio triggers, an added expense.
What actually causes diffusion isn't size and distance. Those are just factors which change the direction if light relative to the object casting the shadows: how parallel the light rays are and how many directions they come from. The impression that lighting is "soft" or "hard" in photo is an optical illusion created by several factors. The biggest clue is how light or dark the shadows are, which is a function of how much fill light there is relative to the highlights.
The goal of lighting control, on a technical level is controlling contrast: fitting the range of the scene -- from highlight to shadow -- to the sensor. Fill is needed in most situations because the sensor in the camera has a limited range of only about 6-7 stops of detail. That means when highlights are exposed correctly with any single light source indoors detail the mid-tones will look darker, and shadow detail. That is also true outdoors in direct sun where a subject with back to the sun will have fill from the sky, but because it is 3 stops darker will render the face darker in the photo than seen by eye.
Single Big source vs Smaller Dual Sources:
Big diffusers, used close enough to an object to dwarf it will cause it light to come from many directions including some angles so shallow the light will "wrap" the object and make the edges of the shadows created by the source look lighter. So what is happening is that the key light is also acting as fill. There is no independent control of the shadow tone, it depends on the size and distance of the light. Also unless the light wraps completely the shadows will have a dark core (umbra) in the center of the shadows. As any size source moves further away the character of the light on the object changes because the light rays relative to source and object becomes more parallel.
Dual light key/ fill strategies control contrast, lighten shadows, and create the illusion not by wrapping the key light but by flrst lifting all the shadows the camera sees up to the point the sensor records detail in the darkest shadows
http://super.nova.org/TP/LE01.jpg
Then overlap all the other key and accent sources on top of the fill
http://super.nova.org/TP/LE04.jpg
The net result is a flash lit scene which exactly matches the sensor with a full range of detail. I first learned that cause and effect with hot shoe flash back in the early 1970s. I had the good fortune to work for the photographer who introduced the idea of using dual flash to cover wedding receptions. We used direct flash: one on a bracket the other on a stand, overlapping the key light on top of the even fill like putting white icing on a chocolate cake. Its a brilliant strategy for wedding work because it allows capturing detail in the bride dress and groom suit at the same time, something impossible with single flash due to the short range of the camera.
When fill comes from the direction of the camera, and key light is put about 45 degrees from the nose of a subject the result is flattering "short" lighting with buttery smooth shadows, even with direct flash. The fill light is flat and neutral, casting few shadows and clues about shape in the photo, but it illuminates everything evenly. When the key light is added on top of it to create the illusion of shape with the highlights the shadow tone created with the fill does not change, except to the extent the key light is close and big enough to have the wrap effect explained above. The net effect of even fill and a key light placed to the side is like a very large source which is brighter on one side. Even with direct flash lights used in a key over centered fill arrangement will produce "soft" looking lighting if enough fill is used to light the shadows. It works because the brain it is conditioned to think dark = hard.
The best approach for lighting is to take advantage of any tool that is available. So in that respect when considering Single Big vs Dual Smaller source the best strategy is to use a large key source with neutral fill and get the best that both offer. Finding the best combination for hot shoe is mostly a matter of budget and logistics for use.
Chuck
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