Oversized, double-concave diffuser for MT-24EX twin flash


Megaloxantha bicolor palawanica, photographed with oversized, double-concave diffuser

This jewel beetle is, of course, Megaloxantha bicolor palawanica me beetle on several occasions while testing out different diffuser designs for my Canon MT-24EX twin flash unit. In the most recent one, I had tried combining SoftBoxes with my oversized concave diffuser and was pleased enough with the result that I thought I might try it in the field. Well, let’s just say the extensions for the flash heads and SoftBoxes attached to them was far too clumsy for field use, and I abandoned the idea after just a couple of hours. Back to the drawing board.

Despite the problems with using the SoftBoxes in the field, I still wasn’t ready to give up on the idea of double diffusion, and I had also learned that extending my oversized diffuser out over the subject (leaving it “open”) produced better lighting than curling it back (as I had been doing). Curling the diffuser back only served to turn it into a convex diffuser, which results in more specular highlighting because the center of the diffuser is closer to the subject than the edges. A concave diffuser provides more even lighting because all parts of the diffuser are roughly the same distance from the subject. Just about that time, I saw a DIY diffuser design by Piotr Nascrecki that, in principle, resembled Alex Wild‘s tent diffuser. It was, however, much larger—like mine, and thus amenable for use with a 100mm macro lens (the macro lens I use most commonly). This resemblance to Alex’s diffuser did make me notice one missing feature—double diffusion layers. That’s when I thought, why not do the same with an oversized diffuser rather than fussing with separate diffusers attached to the flash heads? I had some Bogen Imaging filter sheets on hand (#129 Heavy Frost), so I picked up some 1-mm steel wire at the hardware store, found a Bic pen in the drawer that I could cut in half, and built the diffuser as shown in Piotr’s post. I then secured a second filter sheet above the first sheet by taping the two together along their sides, being sure to ‘bow’ the upper sheet above the bottom sheet to achieve the double diffusion effect. Here is the result (please excuse the iPhone shots):

Oversized double diffuser for Canon MT-24EX twin flash.

Canon 50D with MT-24EX twin flash and oversized, double-concave diffuser.


Better view of the double diffusion layers and Piotr’s “Bic pen” attachment system.

I have big hopes that this will finally be the diffuser I’ve been looking for. For as quick a test shot as the jewel beetle photo above was, the lighting is great and the colors are vibrant—both achieved with typical post-processing. My only complaint is the slightly greater “hot spot” intensity in the lower parts of the highlights in the eyes. This is due to the flash heads sitting near the base of the diffuser, and (as Piotr recommends) a second set of Kaiser shoes will allow me to move the flash heads not only more towards the center of the diffuser but also further above it to help spread out the light throw and even out the highlights. I’ll need to play around positioning the flashes to figure out the best positions depending on the size and distance of the subject—sitting up higher as they are puts them more on “top” than in “front” of the subject, so they will need to be directed downward more than I am used to doing. Even more important, however, is field usability, and I really think this diffuser will prove to be convenient and easy to use in the field—no more gawky arms attached to the camera, the diffuser attaching quickly and easily and, just as importantly, coming off easily and storing flat in the backpack, and large enough to do the job while not so oversized that it gets in the way. Piotr says this diffuser also works well with the 65mm macro lens, so I will certainly be testing that out as well.

Copyright © Ted C. MacRae 2013

12 thoughts on “Oversized, double-concave diffuser for MT-24EX twin flash

  1. How cumbersome is the twin macro flash in the field? I need to get an external flash and the twin flash is probably ideal, but 1) it’s hundreds of dollars more than a normal Speedlight, and 2) it would add a lot more weight to my camera! I shoot hand-held so this isn’t a trivial consideration (saving up for a tripod that’s light enough that I’d be willing to cart it around for hours). Holding a Speedlight off-camera might be the best thing for me right now.

    • I have little experience with a Speedlight, but I don’t consider the twin flash to be at all cumbersome or heavy. All of my photographs are taken hand-held (oftentimes with only one hand while I use my other hand to hold the plant part on which the subject is sitting). I prefer the twin flash because it makes it easier to get the flash heads close to the subject and results in more even lighting with just enough shadowing to make the image lively. If I did use a Speedlight, I certainly wouldn’t want to hand-hold it all the time, as I need the other hand to hold or brace relative to the subject.

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  3. I realize this is an ancient thread, but could you elaborate on Piotr’s bic pen attachment set up? I’m looking for ways to attache my diffuser in a stable manner and am looking for ideas! Thanks. Gabriel.

    • Hi Gabriel – Piotr’s post was not public, and now it seems even I don’t have access to it anymore. Not a problem, as the design is very simple. Take the ink tubes out of two bic pens and cut the pen about 2 inches from the tip. Glue these tips to the face of the MT-24EX flash bracket that fits onto the front of the lens, one on each side of the central opening. Then fashion a length of stainless steel wire into a triangle about 10″ on each side with the two ends meeting at one of the corners. With the wire triangle laying flat on a table, bend the wire up about 4 inches from each tip, then bend the tip back onto itself about 2 inches from the tip. Turn the triangle upside down, tape diffusion material onto the platform formed by the triangle and insert the U-bend of the bent tips into the bic pen holders. It may take some adjusting, but you’ll end up with diffusion material held just above the lens that can be placed and repositioned easily and quickly. Hope this helps.

  4. Hello! I came across this while looking for ideas for flash diffusion via Google. This looks splendid; I do have the MP-E 65, and would love to try this out, but my current frustrations lie in diffusing properly for subjects that are between 5-10 inches away from, say, a 100mm lens.


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