Monday, January 14, 2013

Some Truth about Strobist softbox work

Today, I´d like to talk to you about some facts in light modifying. With the rise of speedlight photography, the invention of flash brackets, speedring adapters and all sorts of toys, so many fellows went out, saying "now I´ve got a perfect studio setup for no money at all" - but that´s not the entire truth.

---NOTE TO EVERYBODY---

Please don´t be offended! I´m not going to rant about your favourite way of light shaping. I use all these techniques listed here myself and they work PERFECTLY. It´s just that I want to show you some minor flaws in the whole idea of modifying speedlights. Let´s go!



First, let´s have a look at the basic studio strobe compared to a speedlight.


The light emission characteristics are fundamentally different. The speedlight was made to project light into the subject´s direction when mounted on the camera. You can´t change that - it was invented to do so! Of course, you can zoom the head, but then it´s still built in a housing with a reflector and a fresnel screen. The studio strobe, in contrast, was invented to provide "REAL BARE BULB" light, ready for modification (that´s because it HAS a real bare bulb in the true meaning of the word).

Note the weird spray pattern of the Sigma EF 530 DG Super:



Rectangular, weird and pretty useless unless you modify it heavily. Point it up a bit and it gives a nice, yet strange flame shape on that blue wall, but that´s it. Not very useful if used naked and that holds true to every speedlight. So there´s not much use for barn doors or normal reflectors. It´ll always throw out this useless pattern. Okay, but what about a softbox?

Let´s see what the studio strobe does inside a softbox:


Okay, so you see, because of its bare bulb characteristic, it emits light about everywhere in the box from where it bounces back and around, being diffused twice before it leaves the front of the box. No matter how much you squint (or stop down, that is), you will always see a perfectly even white surface, when you look at the front diffusor. Here´s what a speedlight does:

The beam is directed forward, even if you pull out your diffusor panel and zoom back to 21mm or whatever you can do. There will be a hotspot on the inner diffusor which will continue to the front diffusor. It won´t be visible when you look at it or photograph it with flash power relatively high to the chosen f-stop, but when you see a reflection of it, the hotspotting becomes visible (this goes for cooking pot photography, shots of any other shiny reflective object and, sadly, for portrait photography, where it can be seen in the catchlights in the person´s eyes. Any reflection swallows a stop or two, revealing the effect). The inner silver coating doesn´t help much with diffusion here, because the spdlght doesn´t send any direct light there.
I used a speedlight in a softbox as white blown-out background for my pumpkin shot. I had to diffuse again, using a large WD sheet and still had to ´shop it a little to get rid of the vignetting. See "The High-Key Still Life", below.

What else can we do?

Many of you will use a reflective or shoot-through umbrella, because they produce wonderful light and are a cinch to storen transport and set up. But again, there is a hotspot. In practice, it doesn´t matter, but again, you´ll be able to see it in the catchlights.


Here´s my EOS 3 again. It was lit with umbrellas. The light on the device is flattering, but look inside the lens: you can clearly see that there are two hotspots inside that umbrella structure. Problem is, they are asymmetrical due to the off-ness of the flash head (it´s always above the umbrella center and that´s where the hotspot rests). This only shows up in less confusing reflections than those inside a front lens. Unfortunately, peoples´ eyes reflect VERY clear.

Okay, so what about a simple WD gel as a diffusor?


Now, this ist what most people don´t get. You want flattering light? You need a BIG light source. It´s very simple. Putting on a WD gel, a yogurt cup, Gary Fong stuff or whatever is out there, is a great idea for event photography and everything else where you are forced to keep your flash on-camera and move rapidly. Heck, even pulling out your bounce card helps! But remember: you don´t increase the size of your light source, you don´t lose the ugly tiny catchlight that the strobist-man is up against - you only spill more light everywhere else. Of course, you produce much, much nicer shots than if you´d flash everybody directly in the face. But you lose a lot of power. The WD gel even reflects a lot of light to the rear.

"So... how about a speedlight with WD gel inside a softbox. Should give me less hotspotting, huh?"

Um, yes, But only if you can afford the loss of power. Feel free to do so! But for now, let´s not talk about a simple gel as a light shaping tool.

"Damn, is there nothing I can do to mimick a real studio strobe?"

Let me think... you´d need a light shaper that blocks the direct flash from the speedlight and then diffuses it nicely.
Enter the BEAUTY DISH!

There you go. The speedlight-powered dish will only show absolutely marginal differences from one with a studio strobe inside. Plus, it´s a great light shaper. Put the white sock on and it´s a much better softbox than a softbox for potraiture. It also takes honeycomb grids to prevent light spill. It gives flattering light. Add to cart.

"Any last words then?"

Yes. Bounce! Bounce against ceilings, bounce against handheld reflectors, against white kitchen cupboards, washing machines, refrigerators, utility bills, bags of cocaine and letters of resignation. As long as it´s white, it´ll do a good job.

I hope you enjoyed reading. Thanks for your time!

ADDENDUM:  I must add something to this post. Let´s see a shot of a Bowens Beauty Dish in action with a studio strobe:



I guess, that´s what a dish is supposed to do. Now, let´s bring a speedlight-to-Bowens-adapter into play. It looks like this:


On with the dish, starting with the zoom head of the flash at 35mm:


Whoops! See what´s wrong? There´s spill around the deflector and I didn´t hit the direct center of the deflector, so there´s a dark spot as well. (Damn! I wish I hadn´t done that bloody test...) Okay, let´s zoom the flash to 85mm to see if we can stay within the deflector disc:


Ummmm....no. Let´s make a desperate move. This is an original Bowens dish, so I can take off the deflector and put it on in reverse. So I´ll turn convex into concave. That should help spray light into the dish a bit more. Also, I can push it one step closer to the flash, becaue there is a second recess in the rods that hold it.

still 85mm, but deflector disc reversed and pushed in

Thank God, that dunnit.

I haven´t used a real dish so far, but the very similar Bowens Softlite Reflector which not only has smoothed silver finish inside, but also two layered deflector shields. Thus, I never had a problem with spill from a speedlight.

Okay, note to everybody including myself: Before you get into the cost and hassle of adapting your flash to a real dish, just to find out that its quite a pain getting it right - go and get yourself a Calumet Hex21, Aurora or any other collapsible hexagonal box designed for speedlight use. They are fantastic, I own the Hex21 myself and have seen an Aurora in action. Also, a dish doesn´t fold... more than once.

3 comments:

  1. Replies
    1. Great explanation!
      Can you answer this question:
      the camera's f/stop is pretty obvious, but what does an f/stop mean on a speedlite? I always flash manually to get what I want, but using the flash's f/stop setting doesn't really compute to me.
      What do you say?
      Thanks!
      Ches
      Columbia, SC

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    2. Well, in terms of light the f-stop is the full-step increment or decrement of light output of your flash. One stop is half or respectively double the power, thus adjusting your camera's f-stop contrarily should give you the same exposure.

      But you probably refer to the "flash's f/stop setting" as the display that you find on the back of your speedlight... well, as a manually lighting photographer, you can forget about that. It is the device's recommendation for the longest or optimum distance it can light at any given ISO and f-stop. This is for the two people on earth who still flash on-camera and calculate their guide numbers in their heads. As you obviously use off-camera flash, all you have to care about on your flash is the power setting. And the zoom head, of course.

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