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Many speedlight-style flashes have a pull-out / flip-down wide angle panel built in. This isn't really meant as a light modifier, but is intended to help the flash provide better coverage at wide angles.

It seems to me that, in addition to zooming the flash head to the widest setting, it's probably best to use this panel when shooting with a portable softbox. (Or, I guess a large softbox, for that matter.) But I don't want to just do things based on superstition; does anyone have solid information on whether this makes a difference, based on evidence or experience?

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Short answer:

Yes, totally worth it, unless you want your softbox light to have a hot-spot and falloff.

Details:

Okay, so I was inspired to actually test this out, and with Stan's suggestion, to also add a Sto-Fen push-on diffuser to the mix as well. (Slight off-topic note: just as the wide-angle panel isn't really a light softener by itself, push-on diffusers like the Sto-Fen are not actually meant as diffusers on their own. Instead, they give a "bare bulb" effect. See this Q&A for more.)

The Setup

Westcott Rapid Box 10"×24" Strip with Cheetah Light V850 (radio trigger hotshoe flash). I dialed the flash power back to ¹⁄₁₂₈th, and selected a relatively narrow aperture and low ISO. First I tried the flash zoomed in at its 105mm setting, as a control. Then, zoomed out to 24mm. Next, at 24mm with the wide-angle panel, and finally with the push-on diffuser.

The Results

softbox plus wide panel test

Frankly, I was surprised by how much of a difference it makes. I knew the 105mm setting would cause a hotspot, but 24mm isn't really much better. So, the take-away is: use the wide angle panel or a push-on diffuser.

It's a little hard to judge between the last two. The push-on diffuser gives a softer overall pattern, but the hot spot that does exist seems more concentrated in the center. On the other hand, that spot doesn't reveal shadows of the internal structure, which the one with the wide panel does. So I repeated the last part of test with the same flash power but the aperture down another stop. And I added a shot with the wide panel down and the push-on diffuser:

test of wide panel vs. push-on

Again, mostly inconclusive. The doubled-up last shot is darker, but on careful inspection, I don't think the falloff is any less; I think we're just wasting light at this point.

Also note that the apparent darker shadows in the center of the hotspot with the wide-panel test are only relatively darker — that's still brighter than the top and bottom of the box. And that center spot with the push-on diffuser is still brighter than the brightest parts of the hot spot from the panel. This is probably getting to the point where the construction of your particular softbox matters most of all, followed slightly by the light pattern of your particular flash and the construction of the wide panel or push-on diffuser.

Conclusion

So again, the take-away is: use the panel or a push-on diffuser for more even light. Doing both together doesn't seem to be much use.

Oh, and what's the weird black shape at the bottom? The back reflective fabric wasn't quite straight, and that's the shadow. I'll be a little more careful about that where it matters. If the flash power is higher, that all blows out and the whole rectangle is apparently white.

See also

I did a similar test with the 26" Octa, including with and without Westcott's deflector plate. Again, the conclusion is that a push-on diffuser is an important addition.

  • Other random fun finding: at ¹⁄₁₆th power, the Cheetah Light flash can keep up at 8 fps until my camera's buffer filled (20-something frames). Not sure if that's useful but it's kind of fun. – mattdm Feb 28 '14 at 22:32
  • That's the new Li-ion battery flash, right? As far as I know, front snap-on accessories for the Canon 580EX will fit it (same as the Yongnuo 560/II/III), and a dome diffuser/Sto-fen (which turns the flash into a pseudo bare bulb, with significant side emission) helps a speedlight a lot in a softbox. (They're originally meant to be a combined reflector and diffusion panel for studio strobes, after all, even if the speedlight strobist world has gotten hold of them.) It'll cost you half a stop (and around six bucks ea for generics) but they'll be worth it. – user2719 Mar 1 '14 at 6:37
  • @StanRogers Yes, that's the one (I got it mostly for the remote power-level control). Thanks for the tip — I'll pick one up in the right size and add it to the test. – mattdm Mar 1 '14 at 9:13
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The softbox itself will have a hot spot where the middle is brighter than the corners. The additional diffuser would spread the light more evenly inside the softbox and reduce this hotspot. That would translate to flatter light and less hotspots in your image.

If you use the softbox without the additional diffuser your images should be soft but still have sparkle and be more lively.

So, if you want a more lively image don't use the additional diffuser, or do use it for a flatter image. It depends on the look you want.

  • Thanks Jason. This is absolutely spot on and very helpful. I've gone and accepted my own answer, though, because I included pictures. :) – mattdm Mar 6 '14 at 4:29
  • Good test! I usually do a similar test where I put the flash sideways on the floor so that I can see the shape of the light that is emitted. This would also let you see if any light was leaking out from the back of the softbox which could give you inconsistent results. – Jason Sweeters Mar 6 '14 at 17:56
1

Yes, it is going to cause more diffusion, anything that scatters light is going to diffuse it, but how much of that light is diffused and becomes usable light for the softbox is another question.

The exact overall impact is going to depend primarily on the size of the softbox and the distance of the flash from the screen of the soft box. If the flash wasn't already covering the entire screen, it will make it so that the screen is covered more evenly and you'll get the biggest gains.

If the screen was already covered entirely, then further dispersing the light within the soft box is going to bounce the light off the side walls (possibly multiple times). You'll lose some power overall from the extra reflection, but it would still be more diffused. The question of if that extra diffusion is worth the drop in power is really up to the needs of your situation though.

Personally, I end up doing a mix of with or without the wide angle diffuser when I'm using my soft box. If I notice hotspots still I'll flip it down, if not, I'll leave it up to keep my power high, though I also use a diffuser that has a built in center hotspot suppression (thicker material in the spot where the majority of the flash energy hits that reflects more of it back around the soft box.)

If you want to test it more experimentally with your particular flash and softbox, if you have the ability to use the flash off-camera, then you could set it to a manual power level you want to test and adjust the exposure so that you can see the amount of light on each part of the softbox. That should show you objectively how much of the light is coming from each part of the screen from a given angle.

  • So just to be super-clear: do you often actually often notice hotspots in practice that go away when you flip the wide-angle panel down? (And out of curiosity, with which softbox?) – mattdm Feb 28 '14 at 20:33
  • @mattdm - Not regularly, but if I'm in particularly close and people have a particularly shiny makeup I sometimes notice and flipping it down did seem to help a little. I use the Lumiquest softbox. – AJ Henderson Feb 28 '14 at 20:41
  • Thanks. The Lumiquest is pretty little, right? I'll test with mine and see what results I get. – mattdm Feb 28 '14 at 20:52
  • @mattdm - I think it is like 8 inches or so across. I forget exactly, it's designed to be able to used on-camera without interfering with normal operation, so it isn't that big. – AJ Henderson Feb 28 '14 at 20:54
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I just put my flash meter up with a bare flash (SB800) at 1/8 power. With the flash zoomed in to 105mm from about 4' away I got a reading of f16 at ISO200, then with the it at 24mm the reading was f11, the diffusion panel gave a reading of f8, and then stofen was f5.6.

This makes sense because you're spreading the light out over a larger and larger area, therefore the meter receives less and less light in it's little dome.

I do think however, that in this Apollo Orb that I just picked up where I'll be using 3 flash heads and bouncing them off of the reflective umbrella back before it hits the front diffuser, I'll leave the flash heads at 24mm and adjust from there.

  • Thanks, Tony. Yes, it's well-established that changing the flash zoom changes the guide number. You can find this in the manual of most decent flash units, usually as a chart or table. I'm not quite getting the logical leap to the diffusion pattern, though. Can you expand on how this answers my question? – mattdm Oct 11 '15 at 6:57

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