No assistant? No problem — a guide to mobile light diffusion

Feb 16, 2020

Dan St Louis

We love it when our readers get in touch with us to share their stories. This article was contributed to DIYP by a member of our community. If you would like to contribute an article, please contact us here.

No assistant? No problem — a guide to mobile light diffusion

Feb 16, 2020

Dan St Louis

We love it when our readers get in touch with us to share their stories. This article was contributed to DIYP by a member of our community. If you would like to contribute an article, please contact us here.

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Hi — My name is Dan St. Louis, and I’m the Owner and Head Photographer at HeadShots Inc, a San Francisco-based photography service focused exclusively on professional headshots.

In the regular course of my business, I often take headshots at outdoor locations across San Francisco. For a long time, I struggled to get great portraits on sunny Bay Area days.

I haven’t seen anyone else using the following technique, so I thought I’d share, to help other photographers out there avoid the same issues!

Some Challenges With Outdoor Portraits:

So, when trying to get great portraits in outdoor settings, there are a couple of problems that will be familiar:

First, depending on cloud coverage, shots with a pleasant background and in the shade can be underexposed/uninteresting. We typically want about a half-stop more light on the subject vs. the background to get a nice halo effect, but that shot isn’t always available at any given location. Direct sunlight is also obviously a no-no.

Oftentimes the angles I need to use to get a shot in the shade have a dumpster, porta-potty, or some other generally undesirable object in the background. I work primarily for lawyers, consultants and entrepreneurs, and these clients don’t necessarily want a gritty “urban” street vibe around them.

Second, I’ve been kicked out of many, many public spaces in San Francisco — so I need to move fast, before getting booted. Most cool-looking public parks require a commercial license if any piece of photography equipment is touching the ground. And frankly, the hassle/expense of getting those forms submitted isn’t worth it for a single headshot session. So I can’t use a traditional set of tripods and stabilizers.

Third, I don’t want to pay or spend the time coordinating with an assistant to stand there holding a diffusion disk. A) It’s annoying to have to line up an additional schedule  (my clients and I are busy enough without adding a third person to the mix), and B) I’d rather not add that expense to my service offering.

Adventures With Traditional Light Diffusers:

So begins my adventures in using traditional light diffusers.

First, I tried a traditional circle diffuser, and just held it by the rim with one hand.

Photo from Amazon

Unfortunately, I couldn’t manage to hold the disk steady while also holding the camera.

Then, I tried one of these “Handheld” diffusers:

These puppies flap in the wind like ____

These tripod diffusers can be handy indoors, but they’re a pain in the butt to control when there’s even a hint of wind. Also, all of the versions on the market are too small to cover the subject’s entire torso.

The System

So, finally, I created a combo of the two tools.

My three best friends. Studio Arm + Circular Diffuser. Cold brew is optional.

Note: I needed to add super glue to the cap of the studio arm in order to keep those puppies from popping off during the shoot.

The kit I’ll be suggesting here involves:

1. A light diffusion disk. Any brand is OK — I’ve used different ones before and ended up with similar results.

2. This indoor studio arm (similar B&H link)

This is the end result:

Note, I bought several versions of that arm before, but Selens is the only brand that’s worked for me (again, not an affiliate, just giving credit where it’s due :) ). I also had to make some modifications in order to stabilize the disk. If you’re curious about more details, just email me at to get the latest version I’m using.


The core concept here is that light diffusion is your absolute best friend in outdoor shoots. It gives you a ton of flexibility and mobility when selecting poses and backdrops for portraits.

But, you need a studio arm in order to stabilize the disk and adjust it to the subject’s pose and desired level of exposure.

Depending on the strength of the sunlight, you will need to keep the diffusers somewhere between 1.5 and 2.5 feet from the subject. Too far, and the lighting will be flat. Too close, and the subject will be overexposed.

You’ll want the diffusion disk between 1.5 and 2.5 feet away from the subject.

Here is the end product from that shot:

This is a decent shot overall,  but the lighting is a bit flat on the subject’s face, because I have the diffuser too far away.

In order to properly highlight the irises and fill in the eye sockets, you should hold the diffuser as low as possible in relation to the subject. Holding the diffuser to one side of their face will also add more depth to the photo.

Bingo! When held at the right distance, you get flattering light that isn’t too flat. Clients love the natural magazine-style look that light diffusers plus sunlight create.

You can also use the arm to bounce light upward via the white reflector. This kit is particularly useful when diffused light from a cloudy day is coming from behind the subject.

You’ll want to hold the reflector as close to the subject’s face as possible, while avoiding white color cast.

Example reflector shot:

The hand-held reflector increases exposure on the subject and helps fill in their eye sockets.There’s still a bit of shadow in the eyes here, but at least it’ll be fixable in Lightroom without a major undertaking. Without the reflector, though, this shot would have been way too backlit.

Some notes on limitations

If the subject is sensitive to light, you might struggle to get them to keep their eyes open for extended periods of time when using the diffusers. In that case, I would move them into the shade and use the reflector disk instead.

As you’re shooting with one hand, your two big enemies are camera shake and wind.

To address camera shake, you’ll likely have to increase exposure compensation + ISO to keep a tight shutter speed. I wouldn’t shoot at any shutter speed slower than 1/250. I shoot at +1.7 Exposure Compensation, and between ISO 1000 and ISO 1250. If you shoot at a lower ISO, the subject will likely be underexposed and/or blurry.

As for wind, you’re still basically holding a big sail up in the air, so you’ll have to 1) Shoot between gusts of wind, and/or 2) Jam the end of the stick against a street sign, tree, etc. to stabilize the device. Both methods can be helpful.

Metering your shots is tough and can create a lot of overexposed photos. I’ll typically spot meter on the brighter side of the subject’s face to avoid this problem.

There are still some problems with this device as I’ve constructed it, so I’m working on a Version 2.0, but for now, it’s a critical part of my gear list, and of keeping my operation tight — no off-camera flash and no assistant needed!

More samples of hand-held diffuser shots:

Mobile diffuser in broad daylight in front of GG Bridge:

Diffuser placed directly in front of subject to create flatter light in broad daylight:

About the Author

Dan St Louis is the Owner and Head Photographer at HeadShots Inc, a headshot photography studio based in San Francisco. To see more of his work, you can go to his website and follow him on LinkedIn.

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7 responses to “No assistant? No problem — a guide to mobile light diffusion”

  1. Zack Schindler Avatar
    1. Motti Bembaron Avatar
      Motti Bembaron

      Almost $50 for that? No thank you.

  2. Motti Bembaron Avatar
    Motti Bembaron

    To our Canadian readers, here is a link to vastly more affordable solution:

    1. Daniel St. Louis Avatar
      Daniel St. Louis

      Have you tried that one? I think I bought that one and the clips which attached to the diffuser exploded within 10 minutes of my first shoot with it. I’d be open to recommending a cheaper one though.

      1. Motti Bembaron Avatar
        Motti Bembaron

        I have something very similar. It’s plastic and does not hold much but definately strong enough for a small reflector or a speedlight. I now use a reflector that has a handle and it is much easier to hold.

  3. Eranda Abeysinghe Avatar
    Eranda Abeysinghe

    Cool setup , having the cam on a monopod migt work too

    1. Daniel St. Louis Avatar
      Daniel St. Louis

      Thanks! I may try that.