Size matters; Comparing Octabox sizes with high speed sync

One of the questions I see pop up often through various portrait groups on Facebook is “what softbox do I buy?”. After they settle on an octabox, it’s invariably followed up with “How big should I go?”. Personally, when it comes to Octaboxes, I’ve always been of the belief that the bigger the better. But, that’s just because I like nice big soft light. And, if you’re using a flash capable of filling it, why not?

In this video from photographer Francisco Joel Hernandez, we’re shown how they measure up in a direct comparison. Using 18″, 38″ and 60″ we get an overview of how size affects how the light falls on your subject. We also get a look into some of the more practical reasons why you might choose one size octabox over another.

The biggest visible difference between the three boxes is the softness of the light they produce. As the light source (the front of the octabox) gets larger, the softer the light becomes on your subject. So why would you want to use a small 18″ box?

Well, for a start, unless you know you specifically need hard light with well defined shadows, any softbox is better than no softbox. 18″ boxes aren’t generally considered very soft, but they do take the edge off shadows. This helps stop those shadows being so distracting from your subject. The lighter areas just blend into the shadows.

18″ octaboxes also have the advantage of being fairly compact and lightweight for transporting. If you’re shooting out on location and you’re walking a distance to get where you need to be, light weight is the key. Their small size also means they’re far less susceptible to the elements. You can use these in some fairly windy conditions.

Let’s take it up a notch, though, to the 38″ octabox. As you can see, this produces a much softer light. The darkness underneath the chin and behind the arms makes a much smoother transition to the lit areas. There’s also less of the dark areas because the light is creeping in from so much extra space. This is when we start to see that gorgeous large soft light, especially when used closely.

This is starting to get to the size I personally prefer. My own go-to lighting modifier is a Bessel 48″ octabox. It’s a nice lightweight box, easy to pack up and assemble quickly. It gives a nice soft light, and it’s pretty inexpensive.

But, once we’re at this size, as Francisco mentions in the video, the wind definitely starts to play a factor. It doesn’t even need to be a strong wind, either. A quick little gust you can barely feel can easily topple a light with such a modifier. So, this is where sandbags and assistants come into play. If you’re shooting on grass or similar ground, a lightweight option to hold down your stand is tent pegs and bungee cords (one of my personal favourite lightweight combos on location).

A larger octabox offers the ability to cover more area. It lets you get more light on your subject for full length shots. It also allows you to cover groups of several people more easily while retaining some softness of light.

Stepping up to a 60″ octabox gives something more like this. It’s an even softer light, which wraps around your subject even filling in those shadow areas. This is why I love big lights on location. With the sun behind your subject acting as a rim or hair light and an octabox from the front, it’s one of my favourite looks on location.

On the huge 60″ octabox, wind is definitely a big factor. You might be able to get away with a sandbag or two on a 38″ box, but with a 60″, you will almost certainly want the weight of a human assistant to help hold it down. It’s definitely worth the hassle to use one of these though. It offers a beautiful soft even full length portrait light.

You can find out more about Francisco on his website, more of his tutorials on YouTube, follow his work on Instagram, or reach out to him through Facebook. Images used with permission.

How about you? Do you, like me, feel that bigger is better when it comes to softboxes and octaboxes? Or do you prefer a smaller, harsher light? What’s your go-to modifier for using flash on location? Let us know in the comments.