Till today I found the Canon MR 14 EX ring lite flash and the Sigma Flash Macro Ring EM-140 DG.
Has anyone any experience with those flashes and the Canon lens and could share it?
I have had the Canon Ring Lite for about a year and a half now, and it's great! I can set the camera to manual, 1/200 sec, f9-13 and the flash outputs the correct amount of power to give a proper exposure. Since it has two tubes, you can set the ratio for each tube, from 1:1 (both output the same amount of light) to 1:8 (one tube lights 8 times as much as the other.) And that's only in ETTL mode. In manual mode you can select the output of each tube from 1/1 to 1/64.
Since it clips onto the front thread of your lens, you can place the tubes vertically, illuminating from the sides, or turn it and place one tube on top and the other below (my personal choice). This affects the lighting direction. It's also possible to turn one tube completely off.
It also has focus assist lamps, two small lights that illuminate your subject (see pic below) so you can focus. I've used AF in pitch darkness with these lights and gotten great pics and focus, so they work just fine.
It has its drawbacks, of course. The most annoying is the circular reflections you'll encounter on reflective surfaces, such as eyes and shiny bugs. You can see some examples of this on
water drops,
spider eyes I and
II,
frog eyes and
shiny insect parts (look at the tip of the "face"[rostrum]).
The other drawback is that since it's a macro flash, the range is pretty limited. So you better try to keep those bugs close!
Oh, one other cool thing is that this flash can act as a master. This means you can trigger an external flash wirelessly, if it's set as a slave. See the last pic below for a possible setup, and see
here and
here for two comparisons. Top pic is ring flash only, bottom pic is ring flash and external flash for fill light.
All in all, this is a great piece of equipment. I haven't used the Sigma (Or the more expensive Twin Lite), but I'm very happy with my unit, and if you can either tolerate or work around its shortcomings, then you'll be very happy.
Feel free to ask anything you like! FYI, virtually all of my macro pics on my site (link in my sig) were taken with this flash.
PS: All pictures used in this post were taken by me, so if you have a question about a particular pic, shoot!