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MT-24EX Users Guide

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Due to the number of questions I've received I feel the need to do a step by step guide on how I set up and use the MT-24EX and now the MT-26EX RT. But before I dive in there are a few things that you need to understand.

I've spent a lot of time experimenting with the MT-24EX/26EX and looking for a way to get the light I want from a flash that, out of the box, is really harsh. I started by learning how a flash works from reading the HiViz web site and reading the tutorials at Strobist like Aperant Light Size. There is a huge difference between getting good results with a flash and understanding how you're getting the light that you're seeing in your images. If you're not willing to invest a little time to read those two sites then, IMHO, you should stop reading this tutorial now. Odds are I'm going to confuse you in the long run because you're not going to understand what you're doing and you're not going to understand why the things that I do work.

The last disclaimer before we get into the nuts and bolts of things: I am not now, now will I ever be, the last word on any photographic discipline. There are a lot of ways to get from point A to point B and I'm only giving you one of them, my way. Take what you read here and elsewhere and experiment. Make your photography look like it's coming from you and not me otherwise you will always be walking in my shadow.

Let's get started by going over what I've learned about ratio control on the MT-24EX. With ratio control you can vary the power of the flash heads to create deeper shadows, but it has some limitations...

With E-TTL flash metering the camera will send out a pre-flash that's used to determine the exposure for the scene, and then it sets the power of the flash heads for the main flash burst. With ratio control you're telling the flash to take the total amount of light that the camera want's to use for the scene and send more of it out a single flash head. But the total amount of light that the flash produces is the same with or without ratio control, in other words ratio control is not the same as flash exposure compensation (FEC). So with ratio control enabled you run the risk of over exposing part of the scene, and it's been my experience that the E-TTL pre-flash is not affected by ratio control (or if it is it doesn't have any effect on how the camera is metering the scene).

You do not need ratio control to get good shadows, so turn it off. The only time you should have ratio control enabled is if the flash heads are 180 degrees apart on the flash mount and even then if you have the heads angled differently you still don't need ratio control. If you do feel the need to use ratio control then don't set it higher than two to one, and keep in mind that I do not use it.

I usually have one flash head at the top of the lens (the key) at the 12 O'clock position and the other flash head is off to the side (the fill) at about the 3 O'clock position (relative to me) on the flash mount that Canon supplies with the MT-24EX/26EX. I also use a Kaiser Adjustable Flash Shoe to get the key flash higher, and at a different angle, than the fill to cut down on glare. If both flash heads are  mounted directly to the Canon flash mount then the angle between the flash heads, subject, and sensor will be the same -any shiny surface is going to cause problems since both flash heads will be hitting the same spot at the same angle. The Kaiser Adjustable Flash Shoe is not "keyed" to clip into the Canon flash mount, but I cut two groves in mine with a Dremel tool so that it locks in place like the MT-24EX's flash heads.

The angle of the individual flash heads can also make a big difference. I usually keep them both pointed directly at the subject. If I'm getting some glare that I don't like and I have time to correct it then I'll angle the flash head that's causing the problem either toward the lens or toward the subject (it depends on the scene). Also the magnification that I have the MPE-65 set to determines how I have the flash heads angled, and it's kinda tough to show it in a photo so I'm going to do my best to explain it.

If you own the MT-24EX/26EX then you know that the flash heads make a clicking sound when you move them up and down. So as a starting point push the flash heads all the way down so that they are pointing toward the lens. For life size bring both flash heads up one click. For twice life size and higher magnification leave both flash heads all the way down. My method of angling the flash heads at the various magnifications keeps them pointed directly at the subject, and it keeps the flash duration short. In some situations you might what to change the angle to eliminate bad reflections, but the angle that I set the flash heads to works most of the time.

You can also turn the flash heads from side to side, and you might want to depending on how close the subject is to the background. The way that E-TTL metering works is that there is a pre-flash before the main flash fires that the camera's light meter uses to set the exposure for the scene. If very little of that pre-flash makes it back to the camera (it can happen if the background is more than 6" or about 15cm from the subject) then the background will be very dark or black and the subject will be over exposed because the light meter gets fooled into trying to expose the background. But if you turn the flash heads toward the subject, especially the fill light (the one that I position on the side of the lens) then most of the pre-flash will hit the subject and the meter will give you a correct exposure. Putting something directly behind the subject to reflect the flash back into the camera not only makes E-TTL metering more accurate but can also give you an image that looks more "natural". I'm currently using a set of artificial flowers to keep my backgrounds from being black.

Because the light from the MT-24EX/26EX is so harsh the trick to getting the quality of light that I want from it has been to get the flash heads pointed right at the subject, get them as close to the subject as possible, and to diffuse them with a diffuser built from multiple layers of diffusion material with some space between them. The end result is that people are starting to think that my images are taken in natural light and that tells me that I'm on the right track. My goal when I started experimenting was to get flash photos that didn't look like flash photos. But keep in mind that I'm still learning, still experimenting, and that you should do the same.

One final note: Getting the flash heads close to the subject gives me a flash duration that is extremely short and enables me to freeze the motion in a scene. The resulting images are razor sharp and have a lot of detail even though I'm shooting at high magnifications and Fstops. So if you're not getting the sharpness that you see in my images you might have your flash too far away from the subject, you need to take more control over the motion in the scene, or your diffuser is better at blocking the light from your flash than it is at diffusing it...
A guide on how I use the Canon MT-24EX macro twin flash.

Updated text on 18 Feb 09.
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CC7D's avatar
Thanks again - I'll let you know how the diffuser build turns out