Canon makes two similar macro flash systems, the MR-14EX Ring Lite and
MT-24EX Twin Flash. Both are intended to surround the front of a
standard Canon macro lens, e.g., the
Canon EF 100mm f/2.8 Macro USM, (compare prices) (review), which is the lens used for all of
the example images here.
The MR-14EX Ring Lite has two tubes forming a ring around the front of
the macro lens. This will be a reasonably diffuse light source if the
object to be photographed is small, e.g., less than four inches in
width. Ring lights are among the most uniform light sources,
producing shadowless images with little variation from photographer to
photographer. As such, they are the standard for much medical
The MT-24EX Twin Lite is basically the same hardware, but the two
strobes are packaged into mini shoe-mount boxes. These can be packed
on either side of the lens, in which case the light is similar to that
from a ring light. They can be angled. One or both strobes can be
held off-camera. The MT-24EX offers much more creative control of
light at some risk of operator error.
Here are a couple of typical ring flash photos, both taken with the
Canon EF 100mm f/2.8 Macro USM, (compare prices) (review). These are the kinds of pictures
you might expect a doctor's assistant to create. Notice the
reflection of the ring flash itself in the subject's eye.
Selling Stuff on eBay
Suppose that you discover that your $5000 Rolex is less accurate than
a $10 Timex. You decide to sell it before it needs another $500
cleaning. Let's try a couple of images first with the MR-14ex ring
flash. Note that the first image required exposure compensation of
+2/3 f-stop and the second, due to the glare from the crystal,
required reverting to manual flash at 1/32nd power. Both are with the
100mm lens at f/11. Adjusting relative power between the ring light
tubes did not reduce the glare, only shifted it around.
Here is the same subject with the MT-24ex twin light. Automatic
exposure, compensated +2/3, worked fine for this and glare from the
crystal was not a problem. For the first image, the two strobes
remained mounted to the ring. For the second image, also including
the entire watch, one strobe was handheld above the subject pointing
straight down. This brightened the background a bit.
Selling Stuff on photo.net
Suppose that you had been saving a treasured Canonet QL17 compact 35mm
film camera as a 16th birthday gift for your beloved first-born child.
Upon reaching that age of wisdom, he scorns the gift saying "What's
wrong with you, gramps? Where do you think I could ever buy film for
that thing? Do you really want to destroy the environment with
chemicals anyway? All the cool kids use cell phone cameras." Time to
sell the camera in the photo.net classifieds.
Below are a couple of images with the MR-14EX Ring Lite. Note the
Switching to the MT-24EX Twin Lite and keeping both strobes on the
lens ring, we get very similar images:
Holding one strobe of the MT-24EX Twin Lite off camera results in
substantially more even light:
Adjusting the Output Ratio
Both macro strobes provide for an adjustable output ratio between the
two tubes. The effect of a 4:1 ratio is much more dramatic with the
Twin Lite than with the Ring Lite. Here is a series of Twin Light
images, at 1:1, 1:4, and 0:1 (only the right tube firing). All were
taken with the 100/2.8 USM lens at f/16 and a magnification of 1:1.
The basis of both of these macro strobes is a big power pack that
mounts into any Canon EOS body's hot shoe. The power pack design
appears to have been lifted from the standard EOS system speedlites.
The switches and display are more or less the same. The features are
the same, including ones that wouldn't seem to be useful in a macro
strobe, such as second curtain sync, high-speed sync, and exposure
bracketing. The battery compartment holds four AA cells and there is
a jack for an external power pack.
The main physical difference between the power pack for these stobes
and a standard EOS strobe is that there is no actual strobe lamp. One
or two cables come out from the power pack to attach to the strobe
tubes at the front of the lens.
These are powerful flashes. Unfortunately, in macro work that is not
necessary a good thing. Despite that nobody taking macro photos is
going to think in terms of guide number, Canon specifies the flash
power as if these were conventional on-camera strobes. The Twin Light
has a guide number of 85 in feet at ISO 100. This means that, at a distance
of 20', a properly exposed photo could be taken at ISO 100 and f/4
(divide guide number by distance to get aperture).
Unless the aperture is set to a fuzzy-from-diffraction f/32, which
becomes f/64 when a macro lens is racked out to 1:1, such an abundance
of power is typically unnecessary for macro work. A more interesting
question is how little power the flash can be set to put out. At
optimum sharpness apertures around f/8 and a subject that is only a
few inches from the lens, a huge blast of light is not required,
especially at ISO settings or film higher than 100. The owner's
manual (disappointingly not available online) includes a table of
workable magnifications and apertures. At ISO 400 with a 100mm lens,
for example, the MR-14EX ring light is overpowered at f/2.8 through
f/8. At ISO 100, the flash should work for all magnifications between
0.33 and 1 and all apertures between f/2.8 and f/32. In manual mode,
the minimum flash output is 1/64th of full power, i.e., six f-stops
less than full power.
Both macro strobes can control an off-camera EX-series EOS speedlight
wirelessly. The command sequence to do this is complex enough that
you will need to bring the owner's manual with you, but it should work
well once configured. The off-camera strobe will be useful for
The MR-14EX Ring Lite is the best choice if you need a consistent
series of shadowless photos of small objects, especially if the
photographers are going to be inexperienced. The MT-24EX is a better
choice for creative projects.
Where to Buy
You can get these strobes overnight from amazon.com: