How big of softbox with my speedlight???

And for anyone interested, here are the files as captured with tether and shown by DPP with exposure data and histogram.

I am a lighting novice who wants to put her speedlite into a large or very large softbox.

The new 600EX-RT can zoom to 20mm, which should help. No wires or cords required.

I have one, am ordering two more, for real estate interiors, but realized I should check on this functionality, first.

So, how big of a softbox can a 600EX-RT handle (using two or three in a studio, in various configurations)? I was going to order a 4x6-ish and maybe a strip box.

Don't laugh, but I mostly take photos of my kids hamming it up, one to three at a time, but I am very analytical/technical so this questions has been bugging the crap out of me.

alintx wrote in post #15289489
I am a lighting novice who wants to put her speedlite into a large or very large softbox.

The new 600EX-RT can zoom to 20mm, which should help. No wires or cords required.

I have one, am ordering two more, for real estate interiors, but realized I should check on this functionality, first.

So, how big of a softbox can a 600EX-RT handle (using two or three in a studio, in various configurations)? I was going to order a 4x6-ish and maybe a strip box.

Don't laugh, but I mostly take photos of my kids hamming it up, one to three at a time, but I am very analytical/technical so this questions has been bugging the crap out of me.

Firing up the old trigonometry knowledge and consulting trig tables, I compute that with flash coverage of 20mm lens, a softox which is 48" x 72" (4' x 6') needs to have the flash face about 40" from the softbox face for its coverage to completely fill the softbox face.

With 24mm coverage angle, the box needs to be about as deep as it is wide, for the 24mm coverage to fill its face. So 48" wide softbox needs the flash head to be about 48" deep to fully fill the front panel.

Wilt wrote in post #15289530
Firing up the old trigonometry knowledge and consulting trig tables, I compute that with flash coverage of 20mm lens, a softox which is 48" x 72" (4' x 6') needs to have the flash face about 40" from the softbox face for its coverage to completely fill the softbox face.

With 24mm coverage angle, the box needs to be about as deep as it is wide, for the 24mm coverage to fill its face. So 48" wide softbox needs the flash head to be about 48" deep to fully fill the front panel.

Wilt, using your math skills and table is an interesting intellectual exercise. Unfortunately it has little to do with answering the OP's question.

If you want to fill a soft box with a speedlite its necessary to make it appear as a bare bulb, similar to what one gets from a monolight. There are a couple of ways to do that; a) use the wide angle deflector that is built into the flash head on the 600EX. Another, used by Joe McNalley, is to add a Stofen type omni-bounce to the head. Both will widely disperse the light coming from the embedded tube in the speedlite. They may absorb a portion of the output but not too much within the confines of a soft box.

Its also prudent to expect that the light coming from the front of the soft box may fall off toward the corners. The fall off is a two edged sword. On the one hand it means you may not have even light across the subject. On the other hand it means you can feather the modifier to more precisely control where the light goes.

dmward wrote in post #15289567
Wilt, using your math skills and table is an interesting intellectual exercise. Unfortunately it has little to do with answering the OP's question.

If you want to fill a soft box with a speedlite its necessary to make it appear as a bare bulb, similar to what one gets from a monolight. There are a couple of ways to do that; a) use the wide angle deflector that is built into the flash head on the 600EX. Another, used by Joe McNalley, is to add a Stofen type omni-bounce to the head. Both will widely disperse the light coming from the embedded tube in the speedlite. They may absorb a portion of the output but not too much within the confines of a soft box.

Its also prudent to expect that the light coming from the front of the soft box may fall off toward the corners. The fall off is a two edged sword. On the one hand it means you may not have even light across the subject. On the other hand it means you can feather the modifier to more precisely control where the light goes.

you apparently have forgotten my opening post in this thread, where I use a speedlight with 30mm coverage angle, and it fails to fill the front panel, and if I use 24mm coverage angle it fills the front panel. Just as my trig predicted.

Admittedly with single diffusion softbox, there is a hot pattern + visible, with double diffusion the hot pattern disappears.

If your contention (blue text) were absolutely true, my test should have failed, shouldn't it?! The 600EX covers 24mm without the wide angle lens pulled out; with the wide angle flash lens it covers 20mm, the same as the OP statement about her flash.

Just 'for grins' I'll put my bare bulb Dynalite 4040 into the same softbox with only single diffusion, and shoot the softbox for comparison, and also measure evenness of illumination using incident meter at center and four sides, both with Metz 45CL and with Dynalite bare bulb head.

Wilt, we are not making arguments before the supreme court, we're trying, at least I am, to pass along some useful knowledge based on about 40 years experience doing commercial photography and having to solve lighting problems.

The point here is that for a speedlite to "fill" a large modifier it has to appear to the modifier as a wide angle light source that can take advantage of the modifier's construction. How that wide angle light dispersion is accomplished is relatively unimportant. What's important is that the photographer understand that there are ways to get it done.

dmward wrote in post #15289608
Wilt, we are not making arguments before the supreme court, we're trying, at least I am, to pass along some useful knowledge based on about 40 years experience doing commercial photography and having to solve lighting problems.

The point here is that for a speedlite to "fill" a large modifier it has to appear to the modifier as a wide angle light source that can take advantage of the modifier's construction. How that wide angle light dispersion is accomplished is relatively unimportant. What's important is that the photographer understand that there are ways to get it done.

That above statement I fully agree with! I simply did not want alintx to think that she had to mimic a bare bulb head to properly fill the box.

Thank you both. Looks like I should find a "add a Stofen type omni-bounce to the head" to help things along. 40" seems way too deep for a softbox and would start to defeat the purpose, wouldn't it, by moving the light source farther back (rather than closer to the subject for softening)?

alintx wrote in post #15289691
Thank you both. Looks like I should find a "add a Stofen type omni-bounce to the head" to help things along. 40" seems way too deep for a softbox and would start to defeat the purpose, wouldn't it, by moving the light source farther back (rather than closer to the subject for softening)?

The location of the flash HEAD isn't the factor that contributes to 'softening of the light'...the distance between the subject and the FRONT PANEL of the softbox is what matters, as that is the determinant of 'virtual size'.

Ahhh, good point.

Wilt wrote in post #15289715
The location of the flash HEAD isn't the factor that contributes to 'softening of the light'...the distance between the subject and the FRONT PANEL of the softbox is what matters, as that is the determinant of 'virtual size'.

You said it before I could. Well said.

Heck of a deal....

http://fjwestcott.com …undle-holiday-promo-offer

Alison,
The Westcott Apollos use a different approach to getting a soft light. As noted in the video on the site Harley linked they create an indirect light by bouncing the light into the back of the box.
The box I used on post 15 of this thread is a Chinese knock off. Its available here: http://www.photoloving​.com …catshow/FlashSo​ftbox.html

They call them reflective umbrella soft box. If you have yet to acquire your soft box, these or the Apollos are an attractive alternative.

There one drawback (for me) is limited ability to tilt. I found a solution and discuss it on my blog here: http://dmwfotos.wordpr​ess.com …esting-with-phottix-octa/

Thank you!

dmward wrote in post #15292003
Alison,
The Westcott Apollos use a different approach to getting a soft light. As noted in the video on the site Harley linked they create an indirect light by bouncing the light into the back of the box.
The box I used on post 15 of this thread is a Chinese knock off. Its available here: http://www.photoloving​.com …catshow/FlashSo​ftbox.html

They call them reflective umbrella soft box. If you have yet to acquire your soft box, these or the Apollos are an attractive alternative.

There one drawback (for me) is limited ability to tilt. I found a solution and discuss it on my blog here: http://dmwfotos.wordpr​ess.com …esting-with-phottix-octa/

Wescott has wisely designed a box that helps to reduce the hot patterns caused with direct lens speedlights, and used the reflector design to try to even out the illumination from the front panel of their box.