For clarity on the macro flash adapter kit, it includes:
- 1× Mount Ring A AD-M1-MA
- 2× Flash Head Mount A AD-M1-FA
- 1× One Macro Lite Adapter AD-M1-LB (RF85mm f/2 Macro IS STM)
- 1× Macro Lite Adapter AD-M1-LC (RF24mm f/1.8 Macro IS STM)
- 1× Macro Lite Adapter AD-M1-LD (RF50mm f/1.8 STM)
Canon also launched two additional adapter rings, sold separately:
- AD-M1-RA for RF35mm f/1.8 Macro IS STM
- AD-M1-LA for RF100mm f/2.8L Macro IS USM
There's an error in the description of the kit, which refers to a, "Macro Twin Lite MT-26EX-R"...unless Canon is making a new twin flash that they didn't bother announcing, there's a 'T' missing and the flash in question is the Macro Twin Lite MT-26EX-R
T. This is not a typo on the part of CR, it's Canon's fault. The Canon USA page is wrong (and B&H, et al., mimic the error).
Canon HK gets it right, though:
I do finally understand the purpose of this kit, which wasn't clear to me before.
The $179 kit is designed to enable you to use the MT-26EX-RT with three RF lenses, the RF 24/1.8, RF 50/1.8 and RF 85/2. For an additional $74 and $59, respectively, you can buy the adapters to use the kit to mount the MT-26EX-RT to the RF 35/1.8 and RF 100/2.8. My initial confusion was because there is already a way to mount the MT-26EX-RT to four of those lenses using one of Canon Macrolite adapters, there are 52mm, 58mm, 67mm and 72mm versions available that work with both the older MT-24EX and the current MT-26EX-RT (they share the same mount ring). For the RF 50/1.8, a cheap set-up ring to one of the Macrolite adapter sizes would enable mounting. The 52mm and 58mm adapters are no longer 'current' but they're available used, and in some cases new from smaller camera stores.
Out of curiosity, I tested that approach with my RF 24/1.8, a 52-58mm step-up ring, a Canon Macrolite 58 adapter (which I use on my MP-E 65), and the MT24-EX flash. Though the lens itself gets a little lost among all the other gear, the setup appears to physically work.
It turns out the problem, and thus the need for the new adapter kit, is that the RF 24/1.8's extending focusing mechanism can't handle the weight of the twin-lite setup. When performing autofocus (or even when turning on the camera on), with the twin heads mounted if the lens is held at an angle, the camera gives an Error 60 (problem with lens movement).
Looking closer at the images of the new adapter rings, the back sides that attach to the lens aren't threaded like the Macrolite adapters but rather have a bayonet mount. They attach to the respective lenses via the lens hood mount instead of the filter threads, meaning they remain fixed in place as the inner barrel extends to focus closer. Of the five lenses supported by the kit and two separately sold adapters, the four non-L lenses all have an extending focusing design.
Given that Canon designed a new mount ring for the twin flash heads to clip onto, I presume the attachment to the lens adapters is different from that of the ring that comes with the MT-26EX-RT. That would explain the reason for the $59 AD-M1-LA adapter for the RF 100/2.8L. That lens does not extend with focusing so the Macrolite Adapter 67 will work fine screwed into the filter threads of the lens. I have the Macrolite 67 adapter and the older MT-24EX twin flash (which has the same mounting ring as the MT-26EX-RT), and the setup works perfectly on my RF 100/2.8 lens – in terms of physical attachment and actual use.
