Softbox sizes

[Belle04]

Looking to purchase some new softboxes. You can assume that I don't have anything despite the fact that I do.

I am looking at getting some strip, square or rectangular softboxes. I was going to buy in pairs.

For strip I was looking at 12"x48" (30cmx120cm) or 14"x60" (35cmx150cm).

For square I have the options of: 32"x32" (80cmx80cm)or 40"x40" (100cmx100cm)

For rectangular: 30"x40" (75cmx100cm) or 36"x48" (90cmx120cm).

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

The subject being used with these are human. What type of situations would I be faced with (when shooting humans) that a square or smaller rectangular softbox is going to be preferable?

 

[photolando]

Having shot thousands of portraits over the years I can tell you to get at least a medium size box. This usually starts around 36".

I have a lot of medium size boxes. I have a Chimera Medium rectangle that is 36"x48". I don't use at as much anymore but it's produces a beautiful soft light when placed about 3-4 feet from the subject.

My latest favorite boxes are not square/rectangle. They are Octas. There is something about an octabox that just gives a nicer light. Maybe because you get equal angles of light from all sides of the box but I haven't used my Chimera for a long time now.

With Octas you want to go at least 40" or so. My Elinchrom is 39" but I also have a Glow Para Snap that is 44". For the price, this box is fantastic! The light is soft and pleasing. It's a little deep but for 1/2 body shots and head and shoulders it's great.

The "rule of thumb" is to place the box, whatever shape and size, no more than the size of the box. So a 36x48 box should be no more than 4 feet. And a 44" octa should be about 44". You can place it wherever you want. Closer in the light of course will be softer with a faster fall off and further away it will be harder with a wider fall off.

Same with the strips. Stick with the medium sizes. You probably don't need the large ones and the small ones are too limiting/specular.

 

[Gato Amarillo]

Looking to purchase some new softboxes. You can assume that I don't have anything despite the fact that I do.

I am looking at getting some strip, square or rectangular softboxes. I was going to buy in pairs.

For strip I was looking at 12"x48" (30cmx120cm) or 14"x60" (35cmx150cm).

For square I have the options of: 32"x32" (80cmx80cm)or 40"x40" (100cmx100cm)

For rectangular: 30"x40" (75cmx100cm) or 36"x48" (90cmx120cm).

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

If you'll be shooting full length I'd agree with this, provided your lights have enough spread to fill the large boxes and enough power to use them effectively. If you're doing mostly head-and-shoulders you could go smaller. If you do a lot of full length you might consider an even larger rectangular or square. Or even a very large round or octa.

(With very large boxes studio size and ceiling height can be a consideration, so think about your work space.)

I like the idea of the long strip box if you want to edge light a full length, Otherwise smaller should be fine.

The subject being used with these are human. What type of situations would I be faced with (when shooting humans) that a square or smaller rectangular softbox is going to be preferable?

Personally, I don't see much difference between square and rectangular. As far as size a smaller box might give a bit more contrast and definition in a head-and-shoulders or waist up shot.

And I'm assuming this is for indoor studio type use. Large softboxes outdoors can be a serious challenge.

Gato

 

[John Vickers]

[...]

The "rule of thumb" is to place the box, whatever shape and size, no more than the size of the box. So a 36x48 box should be no more than 4 feet. And a 44" octa should be about 44". You can place it wherever you want.

I guess you mean place the box no further away than the diameter of the (octa)box.

Closer in the light of course will be softer with a faster fall off and further away it will be harder with a wider fall off.

No. The closer to the softbox, the slower the falloff with distance.

The falloff with distance approaches 1/r^2 when the distance is more than a few times the diameter of the softbox. When the distance from the softbox to the subject is less than about half the diameter of the softbox, the light intensity is nearly independent of the distance from the softbox - there's almost no falloff at all.

Jim Kasson wrote about that here: Light falloff vs distance for round sources

He makes some measurements, and includes at the end a graph of the falloff from a uniformly radiating circular disk in free space - an ideal softbox.

I tried to explain it here (on DPReview): Re: Inverse square law and size of source

Same with the strips. Stick with the medium sizes. You probably don't need the large ones and the small ones are too limiting/specular.

 

[Models By Day]

For strip I was looking at 12"x48" (30cmx120cm) or 14"x60" (35cmx150cm).

Strip Lights are for a specific type of lighting. If you use 2 of them one on each side of the model, it will create a dark strip down the middle of the model. However this also depends on how they are positioned.


Refer to the right side of the above diagram only.

In the diagram above the Strip light is used as a rim light. I stopped using the above setup and reduced to only 1 or 2 strobes.

I only ever bought 1 Elinchrom Rotalux 50x130cm

I can post examples with 1 and 2 strip lights.

I use a 5 foot Umbrella , (Photek SoftLighter Umbrella with Removable 7mm Shaft – 60″) it is kinda light a softbox as it has a diffuser on it. Not sure if they even sell them anymore.

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

60" strips might be too large for model photography.

The subject being used with these are human. What type of situations would I be faced with (when shooting humans) that a square or smaller rectangular softbox is going to be preferable?

One think you need to be aware of is the catchlight in the eye will have the shape of the softbox. I personally feel that round catchlights look nicer.

 

[Travis Burnside]

I learned something today. Thank you for this explanation, it helped fill in a gap in understanding that I didn't even know I had.

 

[photolando]

[...]

The "rule of thumb" is to place the box, whatever shape and size, no more than the size of the box. So a 36x48 box should be no more than 4 feet. And a 44" octa should be about 44". You can place it wherever you want.

I guess you mean place the box no further away than the diameter of the (octa)box.

Closer in the light of course will be softer with a faster fall off and further away it will be harder with a wider fall off.

No. The closer to the softbox, the slower the falloff with distance.

The falloff with distance approaches 1/r^2 when the distance is more than a few times the diameter of the softbox. When the distance from the softbox to the subject is less than about half the diameter of the softbox, the light intensity is nearly independent of the distance from the softbox - there's almost no falloff at all.

Jim Kasson wrote about that here: Light falloff vs distance for round sources

He makes some measurements, and includes at the end a graph of the falloff from a uniformly radiating circular disk in free space - an ideal softbox.

I tried to explain it here (on DPReview): Re: Inverse square law and size of source

Same with the strips. Stick with the medium sizes. You probably don't need the large ones and the small ones are too limiting/specular.

Well, no.

If you place a subject say 3 feet from a white background and the main light 3 feet away from the subject and lets say the exposure for the subject it f5.6, the light will fall off in intensity before it hits the background and render it a light gray.

Leave the subject there but pull the main light back say 6 feet AND adjust power so you still get that same f5.6 on the subject, now the background will actually be a lighter gray then before.

Now if you leave the light where it is and move the subject closer and closer to the light, adjusting for exposure, the light will fall off faster behind the subject.

 

[John Vickers]

[...]

The "rule of thumb" is to place the box, whatever shape and size, no more than the size of the box. So a 36x48 box should be no more than 4 feet. And a 44" octa should be about 44". You can place it wherever you want.

I guess you mean place the box no further away than the diameter of the (octa)box.

Closer in the light of course will be softer with a faster fall off and further away it will be harder with a wider fall off.

No. The closer to the softbox, the slower the falloff with distance.

The falloff with distance approaches 1/r^2 when the distance is more than a few times the diameter of the softbox. When the distance from the softbox to the subject is less than about half the diameter of the softbox, the light intensity is nearly independent of the distance from the softbox - there's almost no falloff at all.

Jim Kasson wrote about that here: Light falloff vs distance for round sources

He makes some measurements, and includes at the end a graph of the falloff from a uniformly radiating circular disk in free space - an ideal softbox.

I tried to explain it here (on DPReview): Re: Inverse square law and size of source

Same with the strips. Stick with the medium sizes. You probably don't need the large ones and the small ones are too limiting/specular.

Well, no.

If you place a subject say 3 feet from a white background and the main light 3 feet away from the subject and lets say the exposure for the subject it f5.6, the light will fall off in intensity before it hits the background and render it a light gray.

Leave the subject there but pull the main light back say 6 feet AND adjust power so you still get that same f5.6 on the subject, now the background will actually be a lighter gray then before.

Now if you leave the light where it is and move the subject closer and closer to the light, adjusting for exposure, the light will fall off faster behind the subject.

Sure, but that has nothing to do with softboxes, which are the subject of this thread.

...

Edit: Or are you saying the main light is a softbox?

If so, then unless the softbox is truly enormous - like 5m / 15' in diameter or something - your first two cases will behave as you describe.

In the third case, as the subject gets closer to the softbox - less than about half the width of the softbox - the need to change exposure as the subject moves closer becomes less and less, and the light on the background stops falling off relative to the light on the subject.

Err, in this last case, there may be a problem of where to put the camera.

...

It seems like someone must have tried making enormous softboxes by hanging diffusion fabric off of the rails for backgrounds.

 

[BAK CDN]

There are two distances involved in flash phptography, whether or not softboxes are involved.

There's the flash (or softbox or umbrella surface) distance to the subject, and the distance from the subject to whatever you consider the background.

"Whatever you consider the background" can be a sheet of background paper, or the wll of a room, or an elephant standing behind his trainer.

Assuming you want the trainer well exposed, you can move the elephant closer to the trainer, or farther way, and the elephants skin will be lighter (close to the trainer) or darker (farther from the trainer.)

OCTABOXES: If you properly place a flash inside an octabox, the light will come out in more or less a circle, and you don't need to turn the softbox when you turn the camera from landscape to portrait and back to landscape.

The same applies to square, but all things considered, you'll need the square to be farther from the subject than you'd need an octabox to be.

A possible scenario. A baby held in front of a mother, standing in front of a taller father.

The flash is infront of the three of them

You need the power level to be as even between front baby and back dad.

If the light is right on junior, it will be less on mom, and even more less on dad.

If you move the flash close to the kid, the dad will be darker (more falloff) than if you move the flash farther away from the baby.

So if you want "soft" light and lots of front-to-back evenness, you need a bigger softbox.

MY RECOMMENDATION A two foot octabox and a three foot octabox and two flashguns

BAK.

 

[Belle04]

Looking to purchase some new softboxes. You can assume that I don't have anything despite the fact that I do.

I am looking at getting some strip, square or rectangular softboxes. I was going to buy in pairs.

For strip I was looking at 12"x48" (30cmx120cm) or 14"x60" (35cmx150cm).

For square I have the options of: 32"x32" (80cmx80cm)or 40"x40" (100cmx100cm)

For rectangular: 30"x40" (75cmx100cm) or 36"x48" (90cmx120cm).

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

If you'll be shooting full length I'd agree with this, provided your lights have enough spread to fill the large boxes and enough power to use them effectively. If you're doing mostly head-and-shoulders you could go smaller. If you do a lot of full length you might consider an even larger rectangular or square. Or even a very large round or octa.

Mainly full length with a mix of 3/4 length. Using with Godox AD600Pro or Elinchrom equiv. I do have some larger modifiers like umbrella with diffuser but it is 8mm and Elinchrom use 7mm.

(With very large boxes studio size and ceiling height can be a consideration, so think about your work space.)

I like the idea of the long strip box if you want to edge light a full length, Otherwise smaller should be fine.

The subject being used with these are human. What type of situations would I be faced with (when shooting humans) that a square or smaller rectangular softbox is going to be preferable?

Personally, I don't see much difference between square and rectangular. As far as size a smaller box might give a bit more contrast and definition in a head-and-shoulders or waist up shot.

The only difference I can see is the catchlight and that's really splitting hairs. Maybe more important with product?

And I'm assuming this is for indoor studio type use. Large softboxes outdoors can be a serious challenge.

Yes studio usage.

Gato

 

[Belle04]

For strip I was looking at 12"x48" (30cmx120cm) or 14"x60" (35cmx150cm).

Strip Lights are for a specific type of lighting. If you use 2 of them one on each side of the model, it will create a dark strip down the middle of the model. However this also depends on how they are positioned.

In the diagram above the Strip light is used as a rim light. I stopped using the above setup and reduced to only 1 or 2 strobes.

I only ever bought 1 Elinchrom Rotalux 50x130cm

I can post examples with 1 and 2 strip lights.

I use a 5 foot Umbrella , (Photek SoftLighter Umbrella with Removable 7mm Shaft – 60″) it is kinda light a softbox as it has a diffuser on it. Not sure if they even sell them anymore.

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

60" strips might be too large for model photography.

What would be the result of this?

The subject being used with these are human. What type of situations would I be faced with (when shooting humans) that a square or smaller rectangular softbox is going to be preferable?

One think you need to be aware of is the catchlight in the eye will have the shape of the softbox. I personally feel that round catchlights look nicer.

I do have other modifiers but I'd lean towards strip when needing a rim light for example. Now you've got me thinking of getting a smaller one also for a hair light or something!

 

[Belle04]

There are two distances involved in flash phptography, whether or not softboxes are involved.

There's the flash (or softbox or umbrella surface) distance to the subject, and the distance from the subject to whatever you consider the background.

"Whatever you consider the background" can be a sheet of background paper, or the wll of a room, or an elephant standing behind his trainer.

Assuming you want the trainer well exposed, you can move the elephant closer to the trainer, or farther way, and the elephants skin will be lighter (close to the trainer) or darker (farther from the trainer.)

OCTABOXES: If you properly place a flash inside an octabox, the light will come out in more or less a circle, and you don't need to turn the softbox when you turn the camera from landscape to portrait and back to landscape.

The same applies to square, but all things considered, you'll need the square to be farther from the subject than you'd need an octabox to be.

A possible scenario. A baby held in front of a mother, standing in front of a taller father.

The flash is infront of the three of them

You need the power level to be as even between front baby and back dad.

If the light is right on junior, it will be less on mom, and even more less on dad.

If you move the flash close to the kid, the dad will be darker (more falloff) than if you move the flash farther away from the baby.

So if you want "soft" light and lots of front-to-back evenness, you need a bigger softbox.

MY RECOMMENDATION A two foot octabox and a three foot octabox and two flashguns

I already own modifiers like a 7 foot umbrella with a diffuser. I think I even have a couple 60" octaboxes in storage. The question wasn't about octaboxs and was limited to strip, rectangular and square.

BAK.

 

[Belle04]

[...]

The "rule of thumb" is to place the box, whatever shape and size, no more than the size of the box. So a 36x48 box should be no more than 4 feet. And a 44" octa should be about 44". You can place it wherever you want.

I guess you mean place the box no further away than the diameter of the (octa)box.

Closer in the light of course will be softer with a faster fall off and further away it will be harder with a wider fall off.

No. The closer to the softbox, the slower the falloff with distance.

The falloff with distance approaches 1/r^2 when the distance is more than a few times the diameter of the softbox. When the distance from the softbox to the subject is less than about half the diameter of the softbox, the light intensity is nearly independent of the distance from the softbox - there's almost no falloff at all.

Jim Kasson wrote about that here: Light falloff vs distance for round sources

He makes some measurements, and includes at the end a graph of the falloff from a uniformly radiating circular disk in free space - an ideal softbox.

I tried to explain it here (on DPReview): Re: Inverse square law and size of source

Same with the strips. Stick with the medium sizes. You probably don't need the large ones and the small ones are too limiting/specular.

Well, no.

If you place a subject say 3 feet from a white background and the main light 3 feet away from the subject and lets say the exposure for the subject it f5.6, the light will fall off in intensity before it hits the background and render it a light gray.

Leave the subject there but pull the main light back say 6 feet AND adjust power so you still get that same f5.6 on the subject, now the background will actually be a lighter gray then before.

Now if you leave the light where it is and move the subject closer and closer to the light, adjusting for exposure, the light will fall off faster behind the subject.

This was my understanding as well. It's why with bodyscape the light is almost right next to the subject and the light drops off considerably by the time the light has reach the other side of someone's body. If you backed that light off, the fall off would be slower.

 

[BAK CDN]

This is, I believe te best bet, assuming a biggish room. Be bold.

(But I'd still pick Octaboxes to replace the rectangulars.)

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

BAK

 

[ronscuba]

This is, I believe te best bet, assuming a biggish room. Be bold.

(But I'd still pick Octaboxes to replace the rectangulars.)

I am leaning towards 2x 14"x60" strips and 2x 36"x48" rectangular.

BAK

Something to consider with strip boxes is even lighting. Strip boxes will have stronger light in the middle and less lighting at the ends. 14"x60" is a very long strip box. I prefer 36" or no longer than 48".

 

[photolando]

For most out there, as a mentioned, a medium size, 36"46" ish range is probably your best bet. When I shot senior portraits some 15 years ago, I used it daily and loved the result. The catchlight shape was never a concern. Round simulates the sun, square simulates a window. Indoors portraits, soft boxes are designed to mimic windows, sooo.....

As long as there IS a catchlight. Without one the eyes, look dull and lifeless.

 

[John Vickers]

I learned something today. Thank you for this explanation, it helped fill in a gap in understanding that I didn't even know I had.

This assumes a fairly evenly lit softbox, or a large LED panel with some diffusion in front of it.

Trying to light up a softbox with a zoomed-in speedlight is likely to give a strong hotspot in the middle, unless the softbox has a reflector in the middle to spread out the light.

The hotspot can behave as the main light source, so the softbox gives 1/r^2 falloff much quicker than might be expected just from the size of the softbox.

Conversely, if the softbox has an internal central reflector to spread out the light, it is possible to have a dark spot at the centre of the softbox: in this case, illumination might initially increase as the subject moves away from very close to the centre of the surface of the softbox, along the axis of the softbox.

...

I edited my linked post in the other softbox thread to include another way of thinking about the problem: symmetry.