One of the reasons why I started writing was to answer common questions, and one of them is Whats the difference between the MR-14EX and the MT-24EX?. Im no expert, but I own both of those macro flashes so here is my .02 on their strengths and weaknesses and what really separates them. In a nutshell I could say that the MT-24EX allows greater freedom in where the flash heads are placed and call it a day. But things are never quite that easy are they
One note: Both Canon macro flash units can be used to wirelessly control another flash like the 430EX or 580EX (II). The slave flash shows up as a ratio controlled C channel flash on the macro flashs controller. Its very easy to use and works really well.
The MR-14EX has two semi-circular flash heads built into a circular ring that clips directly on to Canons EF-S 60mm, MPE-65mm, and 100mm macro lenses, and it will also clip on to Canons 180mm macro lens (or any other macro lens) with a macrolite adapter. Canon makes adapters for 52mm, 58mm, and 72mm lenses. The adapter just supplies a groove for the flash head to clip on to. The flash heads are fixed in the ring and cannot be moved, but you can turn the entire assembly to move the position of the flash heads (I normally shoot with one flash head at the top of the lens and the other flash head at the bottom).
The diffuser plastic on the flash heads is a milky white color and produces light that is warm colors really pop. The light is not flat as long as you enable ratio control on the flash controller. I had mine set to a 4:1 ratio so that the A flash head was four times brighter than the B flash head (although a 2:1 or 3:1 ratio might be better) and I placed the A flash head toward the top of the lens by rotating the flash assembly 90 degrease (which also places the B flash head at the bottom of the lens since the flash heads cannot be independently moved). Turning the assembly even a little can make a difference in how the light and shadows look, so experiment with it. You can also turn one flash head completely off and just use the other one. Example Image
Reflections from shiny surfaces are a problem for any flash, but its particularly bad for the MR-14EX. Some people like the half moon flash reflection that the flash heads produce, and some dont. Also since the flash heads are longer than the MT-24EXs the reflections can be a lot more difficult to edit out of an image. In my opinion reflections are not a huge problem for the MR-14EX, but you do need to be aware of it.
The MR-14EX has two modeling lights located between the flashes to help you focus by illuminating the scene for 20 seconds or until you fully press the shutter release, and they are bright and well diffused so they cover a wide area. But you have to press a button on the controller to activate them which means taking your eye off of the viewfinder. After you take a photo the modeling lights turn off, so you have to reach up and turn them on for the next shot dumb
Bottom line: Set the ratio control from 2:1 to 4:1, attach the flash to your lens, and take pictures the MR-14EX is really that easy to use. The quality of the light is extremely good, and E-TTL flash metering is very accurate. Its an excellent choice if you dont need more diversity in the placement of the flash heads and you dont want to spend a lot of time experimenting with diffusers. Very, very, easy to use
The MT-24EX is supplied with a flash mount that clips directly on to Canons EF-S 60mm, MPE-65mm, and 100mm macro lenses, and it will also clip on to Canons 180mm macro lens (or any other macro lens) with a macrolite adapter. Canon makes adapters for 52mm, 58mm, and 72mm lenses. The adapter just supplies a groove for the flash mount to clip on to.
Ive had a love / hate thing with the MT-24EX. The light that it produces is harsh, since the diffuser plastic is clear (what a stupid idea!). So I tried various ways to lessen the glare and most of them didnt work very well. I finally settled on hot gluing a set of Gary Fong Puffer diffusers to the MT-24EXs flash heads. Recently Ive been talking to Quest Couch (owner of Lumiquest) on making a set of diffusers for the MT-24EX, so maybe there will be a good commercial solution soon. Ive tried the set that Sto-Fen makes but they are not big enough relative to the subject unless you have the flash heads really close (shooting at 2x or higher with the heads on the flash mount that Canon provides with the MT-24EX, for example). For an explanation on how the diffuser size to subject distance affects diffusion see this post at Strobist
The MT-24EX has two flash heads that connect to a lens mount. The heads are shorter than the MR-14EXs flash heads and they extend out from the lens about an extra centimeter. You can place the MT-24EXs flash heads anywhere on the lens mount, or remove them and place them anywhere you want. Several third party manufacturers make flash mounts for the MT-24EX. Being able to place the flash heads in a wide variety of configurations is a plus, but in my opinion its not a big deal since the further you get the flash heads from the subject the harsher the light becomes, and the flash duration increases (so freezing motion becomes more difficult). Just because you can separate the flash heads over a meter apart doesnt mean that you should
Ratio control is available, but now I hardly use it on the MT-24EX. I normally have the flash heads set about 90 degrees apart so I can get shadows without using ratio control, or I have one flash head pointed at the subject and the other pointed out toward the background. Being able to use one flash head to illuminate the background in a scene is one of the best features of the MT-24EX, but due to light falloff there isnt a lot of reach. Typically I wouldnt expect to illuminate any object in the background thats more than 12 (~30.5cm) behind the subject when shooting at ISO 100 (increasing the ISO can help to illuminate distant background objects, but you might get more illumination from the natural light in the scene than from the flash).
The MT-24EX has modeling lights built into each flash head, and if you enable a special function on the flash you can turn them on by double half pressing the shutter release and they will stay on for 20 seconds or until you fully press the shutter release (set C.F-9 to 1). So you can turn the modeling lights on without having to take your eye off of the view finder cool! But the lights are yellowish in color and they are not diffused like the modeling lights on the MR-14EX so the flash heads have to be pointing almost directly at the subject or you wont see them in the viewfinder. In one way it makes sense, because if you can see the modeling lights then you at least know that the flash is pointed toward the subject in the image frame. But the modeling lights are useless if you need them, but dont want the flash heads pointed directly at what you are photographing
Another annoying aspect of the MT-24EX is the cables that run between the controller and the flash heads. They are coiled, but still pretty long and they have a tendency to flop around. Not a big deal until you are right next to a critter and one (or both) of the cables move and all youre looking at is a place where an insect use to be. I added my own cable management
to solve the problem, but youd think that Canon could have built something into the flash heads to hold the cables a little tighter.
Bottom line: If you need more control over where the flash heads are placed, and you dont mind experimenting with diffusers, then the MT-24EX is an excellent flash! But dont expect to take it out of the box and get good light quality with it
This shot is an example of all my experimenting with the MT-24EX and Im still looking for new ways to use and diffuse this flash
Shot with the flash heads attached to the flash mount that Canon provides with the MT-24EX. One flash head at the top of the lens and the other is on my right.