Softbox Lighting and Theory

Learn all you need to know about the ever-popular softbox.

In highly informative live photography workshop, where Karl takes a closer look at these versatile modifiers, explaining how they work and what sets them apart from other light shapers.

This show answers common questions such as “What is a softbox used for?”, “What size softbox should I buy?” and “What’s the difference between softbox and umbrella lighting?” Whether you’re relatively new to softboxes or have been using them for some time, this show covers both the fundamental and more advanced knowledge you need to get the most from your softbox.

In addition to looking at the theory and science behind them, Karl also goes into detail about the Inverse Square Law, how this can impact your photography and how you can use it to take complete control of your lighting. He also demonstrates multiple lighting setups, showing you how you can be incredibly creative with just a few lights.

In this photography workshop:

  • Softbox lighting
  • How softboxes work
  • The difference between different softbox sizes
  • Softbox accessories
  • How to use softboxes
  • Understanding the Inverse Square Law
  • Softbox lighting setups

You can also read more about softboxes here.

If you have any questions about this show, please use the comment section below.


  1. Gary Stasiuk

    Question about the inverse square law and large versus slightly smaller softboxes. At one point in the video you talk about buying the largest one you can afford. For the record, I have a half dozen in various sizes. Then you further suggest that a very large softbox can be used at say 2 meters away.. and a smaller softbox could be used a 1 meter away to create the same affect because it is relative from the model where those two softboxes appear to be the same size. I completely understand that, makes sense. However, I am curious as to the inverse square law applied in that situation as the soft light falls across the subject. Is it really the same? Does the falloff happen faster across the face or body when the light is closer?… lets restrict this to a single subject and not worry about the background.. for sure then the light intensity fall off would come into play. I guess my question looks at the contrast of the fall off of the soft light falls across your subject to the point where one size IS better. Or is it so nominal where any difference is relative?

    One last question… I am trying to decide on one more purchase. For whatever reason, I just never found and bought a large octabox. I have several sizes of rectangle, 2mx1.5m, 90x120cm, 30x40cm, strip boxes.. for portraits my key is usually the 90 x 120cm… up close it is very large, although a touch clumsy.. I do have a very small octabox but not a large one.. I’m of the mind that for the right price.. yeah I should buy one. The catch light would be different .. the round shape would make it more convenient.. specially on location. I think in one of the videos you suggest it is a key bit of tech you would suggest. Is it going to make a difference and I should get one, and if so, what size?

    1. Hi Gary, on your first points yes all correct and you can see the effect of the inverse square law fall off on two different size softboxes in this video the fall off on the background is very noticeable and it will be noticeable on the face too however alot depends on how much bounce back there is in your studio or if you use a white reflector nearby which would counter the effects of inverse square law fall off. If we were to determine true lighting effects the only way we could do it accurately is to do it in the blackness of space with no nearby bounce back or a completely matt black big room. Also keep in mind that true inverse square law fall off rates are based on the light emanating from a point light source, as soon as that becomes a softbox or where the light is collimated then the rates change as demonstrated in this video On your second question: My octabox 150 is a workhorse but it’s quite big but equally they are shallow which is very useful, I use it mainly from front above but you need a bit of height in that position. It can also be used from the side effectively too, for completely round catchlights I believe you can buy a circular mask to go over it (or you could have one made) so if you have the space then it’s a great tool for portraits, beauty and some fashion. Whether it makes a difference will largely depend on if you can get it above – refer to your ‘Lighting comparison App’ tool in the resources section for comparisons.

  2. @1:10 :36 this is equally or even more important for video when shooting in horizontal format and wider frame sizes to keep the softbox out of the shot, but still wanting a “soft” light. At a certain distance in a wider frame, the biggest softbox will become too small unless someone makes much larger sizes. 8 foot or 12 foot perhaps and that’s more than likely scrim or bounce off a white wall.

  3. If I wanted to invest in a “continuous light” like the Aputure 600d Pro I have seen in your studio, what softbox modifier would you recommend? I’m pretty sure you cannot use an internal diffuser against the flat face bulb because it’ll get too hot being a continuous light source. What is your thoughts on getting it homogenous without an internal diffuser? Thanks.

    1. Hi Ty, the internal diffusor would be at least 30cm away from the light source in any decent softbox. The fitting is Bowens so I’d imagine there are plenty of softbox options to choose from. A bigger one with more airspace is likely to be better but I would check the manufacturers guidelines before committing.

      1. The softbox I found is 12″ to the middle diffuser, but only 6″ from the middle diffuser to the front diffuser. It is 18″ depth total which is slim. In your expertise, would you say 6 inches is enough space/time for the inner baffle to fill the front diffuser evenly?

        1. Hi Ty, that’s very difficult to answer without seeing it. A lot depends on the diffusion material and the reflective angles and properties of the inside of the softbox. The best way to tell is to take an underexposed picture of the front of the softbox and see how homogenous the spread of light is.

  4. Have you ever considered using a “grid” on a softbox that only has the vertical grid and not the horizontal? This would cut the light spill in the horizontal and leave the spill in the vertical. I am curious if this would retain its softness as putting a normal grip that cuts spill in both directions seem to “harden” the light. I know Roger Deakins uses this method for his feature films. As controlling spill in the horizontal is often more important for the set.

    1. Hi Ty, I prefer to use vertical flags just either side of the softbox instead which stop the spill but then leave the centre of the softbox uninterrupted. You will see me use this technique occasionally but whenever it isn’t necessary to reduce spill then I never bother with grids as they just reduce softness.

  5. Shimmy

    Greetings Karl and the whole team!

    I have my first question after watching most of the lightning videos.
    Is there any difference in lighting between the octaboxes that you’re using and the round softboxes, if they are the same size, depth and used with the same type of diffusion materials (inner and outer)?
    I am asking because the ones that I am using are more of a round shape instead of octagonal, and I have checked on B&H (where I buy a lot of my gear) that Broncolor actually doesn’t have “round ones” same as the brand that I am using seems not to sell octagonal shaped ones (Phottix). So is it just a difference between brands or am I missing out on something?

    1. Hi Shimmy, the main things that you mentioned are the most important, size, depth, diffusion. That’s what determines the primary effects of a softbox, if those things are equal then there would be hardly any difference between and octagon shape or a circular shape other than the catchlight in the eyes.

  6. These lessons are so good Karl! Most of my work is shot in landscape vs vertical, so getting a softbox that close works in some scenarios for me, based on lens choice and my distance to subject, but seeing how u show the softbox further away (out of my wider frames) will help my work dramatically.

  7. Hi, Karl. I was wondering if adding grilles would harden the quality of light, and how many steps should I compensate for doubling the distance of my lamp according to the inverse square law?

  8. Hi Karl, great content, thanks for that! When it comes to the inverse square law, I wonder, to which degree, if any, does a narrow grid “collimating” the light affect the falloff with distance? In theory it should lower it, but is this of practical importance?
    Thanks again!
    Cheers, Harry

    1. Hi Harry, yes in all instances where the light is collimated then the fall off will be less. Grids however are ‘artificial’ collimators as they simply block the light from going elsewhere rather than redirecting it so you are only left with light that can escape forwards whilst a great deal of it is built up as heat and absorbed into the black metal, this is also why you loose so much light exposure with a grid. Fresnels are much better as the light is ‘captured’ and redirected forwards so less loss of energy. The inverse square law is still noticeable over distance though even with a fresnel but true inverse square law is related to light emanating from a point light source (which technically doesn’t exist)- You might like this chapter where I explore the practical implications of the inverse square law more –

      1. Hi again, and thanks again. Thank you for the swift and clear answer plus the interesting link! Highly appreciated!!!
        Have a great day!

  9. Going big, would it make sense to use two strip lights 30×120 without the front diffuser behind a scrim if you do not have a big softbox?

  10. Hi Karl. I’m not good at English and take the time to watch each recorded live for 5 hours. Would you please add captions to all videos for me?

    1. Hi, we are gradually adding captions (and other languages) to all our classes but we have a team of people working on this an unfortunately it takes time, especially to keep up with our live shows. Most of our normal classes have captions though.

  11. Good refresher course. I may get a compact beauty dish by next year. May get a name-brand entry-level single strobe for product photography. Maybe in 24 months work with a model to photography some fashion jewelry for my portfolio too.

  12. Hi Karl,
    Thanks for all this videos, I am learning a lot from you, I am a landscape photographer mostly, and this field is very interesting.

    My question is the following,
    When stiffany is being photographed with the softbox 75 or the the two small 30×120, there are some concentric shades coming from the light, so there is one concentric shading on the background for the 75 shots, and two one each for the 30×120, the concentric lights reduce some when applying the window mask to correct for flare, but its still there. Please could you comment on that?

    1. Hi and thank you I’m very glad to hear you are enjoying the platform. With regards your questions on this video (and any other video) we kindly ask our members if they could detail the time in the videos at which they are wanting clarification that way it becomes easier for myself or one of the team to handle any training support questions and note it down for future reference. If you could reply please with the times I’ll get back to you as soon as possible. All the best Karl.

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